Pigments — Mercury-based red (cinnabar-vermilion) and white (calomel) and their degradation products

This article summarises the history of cinnabar, from its first uses in burials to modern oils on canvas. After a brief introduction on mercury and contamination issues, the article gets to the heart of the topic. First, mercury-based minerals significant for studying pigments, i.e. cinnabar, metacinnabar, hypercinnabar and calomel, are presented. Structural information and properties precede an overview of the geographic distribution of cinnabar deposits. The following section addresses the multiple uses of cinnabar, divided into funerary use, decorative use, lustre and Chinese lacquer production. The use of cinnabar for writing (ink), medicine and cosmetics is briefly described, and a shortlist of uncommon finds is further provided. The following section approaches inherent but less known topics such as cinnabar procurement, trade, production technology, application and alteration. An entire section is dedicated to calomel before concluding with an overview of the analytical methods for the characterisation and provenance investigation of cinnabar.


Premise
This Topical Collection (TC) covers several topics in the field of study, in which ancient architecture, art history, archaeology and material analyses intersect. The chosen perspective is that of a multidisciplinary scenario, capable of combining, integrating and solving the research issues raised by the study of mortars, plasters and pigments ).
The first group of contributions explains how mortars have been made and used through the ages (Arizzi and Cultrone 2021;Ergenç et al. 2021;Lancaster 2021;Vitti 2021). An insight into their production, transport and on-site organisation is further provided by DeLaine (2021). Furthermore, several issues concerning the degradation and conservation of mortars and plasters are addressed from practical and technical standpoints (La Russa and Ruffolo 2021;Caroselli et al. 2021).
The second group of contributions is focused on pigments, starting from a philological essay on terminology (Becker 2021). Three archaeological reviews on prehistoric (Domingo Sanz and Chieli 2021), Roman (Salvadori and Sbrolli 2021) and medieval (Murat 2021) wall paintings clarify the archaeological and historical/cultural framework. A series of archaeometric reviews illustrate the state of the art of the studies carried out on Fe-based red, yellow and brown ochres (Mastrotheodoros et al. 2021); Cubased greens and blues (Švarcová et al. 2021); As-based yellows and reds (Gliozzo and Burgio 2021); Pb-based whites, reds, yellows and oranges (Gliozzo and Ionescu 2021); Hg-based red and white (this paper) and organic pigments (Aceto 2021). An overview of the use of inks, pigments and dyes in manuscripts, their scientific examination and analysis protocol

Introduction
Mercury is the only metal (chalcophile) that occurs in liquid form at room temperature. Due to its colour and form, it has also been called liquid silver, hydrargyrum and, especially, quicksilver, a term, this latter, mainly used by geologists involved in the study of its occurrence and mode of transport (especially in the 1940s/1950s, e.g., Dreyer 1940a(especially in the 1940s/1950s, e.g., Dreyer , 1940bRoss 1942;Krauskopf 1951).
Mercury is classified as a rare element as it is present in low concentrations in the Earth's upper (~0.05 ppm), middle (0.0079 ppm) and lower (0.014 ppm) crust (Rudnick and Gao 2004).
Its multiple uses ranged from measurement tools such as thermometers, barometers and pressure-sensing devices to dental amalgam, batteries, lubrication oils, lamps and other industrial processes and products.
Despite its varied and widespread use, mercury is toxic, and, for this reason, it has been banned for paints since 1990, while mercuric chloride is still used as a pesticide and a disinfectant. The WHO identifies mercury "as one of the top ten chemicals or groups of chemicals of major public health concern", that "may have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes" (https://www.who.int/news-room/fact-sheets/detail/ mercury-and-health). However, natural cinnabar is less toxic than organic mercury (methyl mercury or dimethyl mercury) or liquid mercury. At the same time, the process for mercury extraction can be highly toxic (esp. mercury vapours) as well as the accumulation of methylmercury ([CH 3 Hg] + ), which is mainly formed by the action of anaerobic bacteria 1 (see, e.g., Manceau et al. 2015 and Supplementary materials Appendix 1). Environmental issues have stimulated the creation of an extensive body of literature both focused on specific case studies related to the mining exploitation of geological deposits and of a more general nature, aimed at unravelling the main processes (Burkstaller et al. 1975;Rytuba 2000Rytuba , 2003Horvat 2005;Holley et al. 2007;Levin 2014;Chen et al. 2017).
The first category includes such a large number of research papers that it is impossible to mention them all in this contribution; however, it is useful to point out two important aspects. Firstly, mercury pollution has an extremely vast range. Therefore, it is possible to find clear signs of pollution in soils, waters, flora, fauna and atmosphere at considerable distances from the extraction area, especially in correspondence of river courses. Secondly, ancient and modern working places are often mentioned and investigated in these studies, near and far from the mining district; therefore, they represent "a mine of information" for archaeometric studies on provenance and technology.
Indeed, mercury poisoning is thoroughly documented by ancient literary sources and archaeometric investigations. For example, cases are reported for the Late Neolithic/Chalcolithic (5400-4100 BP) population of southern Portugal (Emslie et al. 2015), for miners buried at the archaeological site of Ranas in the Sierra Gorda Querétaro (Mexico; Serrana culture) 2 and for Southern Denmark and Northern Germany medieval population (Rasmussen et al. 2015). This review will tackle the "cinnabar" theme from multiple perspectives, based above all on its characteristics and use. The main objective is to provide the broadest possible framework for the study of cinnabar rather than address each topic in detail. While the dimensions of a single article would not allow a comprehensive discussion, it is possible to provide an overview of the state-of-the-art to guide both the study and the bibliographic search.
The sulphides are the most abundant, and, among them, the three HgS polymorphs-namely cinnabar, metacinnabar and hypercinnabar-prevail. Among chlorides and halides, calomel, terlinguaite and kenhsuite are significant in the Cultural Heritage studies because they are the only ones found in artworks to date. Among natural alloys, the amalgams have a technological and historical interest (Giumlia-Mair et al. 2014) that, however, go beyond the objectives of this review.
A shortlist of research articles that may help study Hgbearing phases is provided in Supplementary materials Appendix 1.

Cinnabar, metacinnabar, hypercinnabar and calomel
Cinnabar (α-HgS) is bright red mercury sulphide (HgS; Fig.  1), also named κιννάβαρι (kinnabari) in Greek, minium cinnabaris in Latin and šangarf or sīm-šangarf in Persian (the Arabic zinjifra should correspond to red lead). On the etymology of cinnabar and the corresponding names in Latin, Persian and Arabic, the reader is referred to the detailed study by Rosół (2018) and Becker (2021 in this TC). On the distinction between inorganic cinnabar and dragon's blood, or Fig. 1 Macrophotos of A cinnabar from the Almadén Mine, Ciudad Real, Castile-La Mancha, Spain (specimen and photo: fabreminerals.com -Mindat.org Photo ID: 56508); B cinnabar from the Tongren Mine, Bijiang District, Guizhou, China (Arkenstone specimen. Photo credits: Rob Lavinsky, irocks. com -Mindat.org Photo ID: 206087); C cinnabar from Pozo de San Teodoro, Almadén district (specimen and photo: fabreminerals.com -Mindat.org Photo ID: 942728 ); D cinnabar crystals on pyritic matrix from Las Cuevas Mine, Almadén district, Spain (photo credits: Carlos Gonzalez Bargueño -Mindat.org Photo ID: 867406); E metacinnabar with pyrite from El Entredicho Mine, Almadén district (photo credits: Borja Sainz de Baranda Graf -Mindat.org Photo ID: 937144); F distorted cluster of cubo-octahedral metacinnabar crystals, intermixed with hypercinnabar, on quartz matrix, from the Mount Diablo Mine, Clayton, CA, USA (photo and specimen, Jeff Weissman -ID 1035520); G intermixed, highly modified and distorted trigonal/ hexagonal appearing hypercinnabar crystals with cubic metacinnabar crystals, with pale yellow flaky copiapite crusts on crystalline quartz (photo and specimen, Jeff Weissman -Mindat.org Photo ID: 1035520); H calomel from Terlingua Mining District, TX, USA (Arkenstone specimen. Photo credits: Rob Lavinsky, irocks.com -Mindat. org Photo ID: 716834). The CC-BY license does not supersede previously copyrighted material; therefore, these images remain under owners' copyright Hypercinnabar (γ-HgS) is a hexagonal phase (Table 1; Fig. 2), first identified by Mikolaichuk and Dutchak (1965). Later, it was found by Protobyakonova et al. (1971) in Russia and approved by the IMA commission in 1978 (Potter and Barnes 1978) as a new HgS polymorph. This black mineral -which may contain minor Fe-has an undefined hexagonal structure (Table 1; Fig. 2). An intermediate pseudocubic phase (XHgS) has been further observed by Bell et al. (2010) between 467 and 552 K, i.e. below the metacinnabar → cinnabar transition temperature.
It is curious to note that the English word calomel (καλομέλανο, calomelano in Greek) derives from the Greek καλός (kalos, beautiful) and μέλανος (melanos, black). Swiderski (2008) narrates that according to Pereira (1849Pereira ( -1850 the name is "referred to Dr. Theodore de Mayerne's black servant, who was so skilled in preparing the drug that Mayerne called it "beautiful black" in praise of both drug and servant". Soon after, Swiderski reconstructs the history of the name's assignment and, above all, traces the significant correlation between the term and the production of mercury sublimates. Considering the medicinal use of sublimates, the author observes the convenience of a term recalling beauty and honey (μέλι, meli, honey) compared to one that explicitly mentions mercury. The latter would undoubtedly have been more frightening for a patient than the former. In any case, while the name calomel does not refer to the natural whitish mineral, it reflects the characteristic blackening obtained with exposure to light (photosensitivity) or ammonia.
Apart from the literature mentioned above, the phase relations in the mercury-sulphur system have been chiefly investigated by Tunell (1954, 1959), Kullerud (1965), Ohmiya (1974) and, above all, by Potter and Barnes (1978), Mel'chakova and Kiseleva (1990), Sharma et al. (1993) and Ballirano et al. (2013). Stable under ambient conditions, cinnabar converts to metacinnabar between 315 and 345±2°C (depending on Hg%; see Potter and Barnes 1978) or even higher at 673°K in an oxidising atmosphere (=399.8°C in Ballirano et al. 2013). In turn, metacinnabar converts to hypercinnabar between 470 and 481°C. Above these temperatures, hypercinnabar is stable up to 788°or 804°C, still depending on Hg%. The diagrams in Fig. 4 show that the stability of the various phases is directly linked to the stoichiometry (i.e. purity) of the HgS. Moreover, the variation in temperatures is also due to different experimental setups (e.g., in situ, ex situ, under vacuum, in an oxidising atmosphere, etc.).  (9) 218.83 (8) 2 Calos et al. 1989 Fig. 2 XRD patterns (Cu-Kα) and (ball-stick) packing along a, b and c (unit cell shown) of cinnabar and metacinnabar. A Buckley and Vernon (1925); B Ramsdell (1925); C Auvray and Genet (1973); D Lehmann (1924); E Wyckoff (1963) Beyond these thermal transformations, it is worth underlining that metacinnabar can also form at room temperature from mercury iodide dissolution in an aqueous solution of potassium sulphide ).
These occurrences and relative quantifications must serve exclusively as an example as they reflect the state of the art of the studies carried out in each country. On the other hand, the numbers account for more modern exploitation than the actual extent of the deposits. Moreover, some attestations are missing, while others refer to the same mining district.
The list is not exhaustive but it gives an idea of the distribution of cinnabar. In support of what can be easily found online, Fig. 5 illustrates the distribution of the main geological deposits of cinnabar. The occurrences have been drawn based on >250 papers indexed by Scopus; therefore, some information is missing but can be recovered on the mindat.org database. In Supplementary materials Table 1, the deposits shown in Fig. 5 are listed together with the corresponding bibliographic reference.
Quartz/chalcedony and barite are the most common gangue minerals, followed by calcite/aragonite and kaolinite.
To summarising, cinnabar is mainly found in volcanic environments and hot springs deposits. It is often associated with stibnite and other Hg-, Sb-and Pb-based phases, as well as with gangue minerals as quartz, barite and calcite. In some archaeometric publications, we read that a cinnabar deposit's limited size may have prompted local populations to obtain supplies elsewhere. While this assumption is undoubtedly  Table 1 valid for industrial applications and thus related to the modern world, it seems less effective when applied to ancient civilizations.

The multiple uses of cinnabar
Cinnabar has been mainly used -To paint human bones and offerings (funerary use).
Based on the archaeometric evidence available so far, the first use of cinnabar appears related to funerary practices and ceremonial activities. To the best of my knowledge, the 9 th millennium BC painted plaster skull from Kfar HaHoresh in Israel (Goren et al. 2001) represents the oldest attestation of the use of cinnabar as a colouring pigment. Similar examples increase when dealing with the Late Neolithic and especially the Chalcolithic periods.
The following section "Funerary use: esoteric power, social self-representation and archaeological evidence" is entirely dedicated to this topic. -To decorate architectural structures and mobile objects (decorative use). Based on archaeometric data, the decoration of ceramic vessels, sculptures and cartonnages precedes that of wall paintings. Over time, the use of cinnabar to decorate structural elements increases considerably while its use for ceramics apparently disappears. This topic is discussed in the section "Decorative use: cinnabar over time and space". -To write (ink in manuscripts). The use of cinnabar as ink is frequently attested, especially during the Middle Ages (see, e.g., Vlad et al. 2011;Serhrouchni et al. 2019;Safronov and Sozontov 2020). For the discussion of this topic, the reader is referred to  in this TC. -To enhance the reduction in lustre production, addressed in the section "Cinnabar for ceramic lustre". -To colour red lacquers, addressed in the section "Cinnabar in lacquered objects". -To serve for medicinal and cosmetic purposes (pharmacological use). Long-lasting use of mercury compounds is attested in ancient and oriental medicine, for example, in Indian Ayurveda (Murthy 1983), Oman (Hardy et al. 1995), Japan (Yamada et al. 1997), China (Anonymous 1967;Wu et al. 2002;Huang et al. 2007;Liu et al. 2008;Jain et al. 2019) and ancient Tunisia (Huq et al. 2006). The numerous therapeutic indications of cinnabar (esp. mercurial salts and other Hg-based compounds mixed with ointments) included fever, insomnia, lice, stoke, trauma, mouth ulcers and syphilis (Liu et al. 2018a). A further indication of the importance of mercury compounds in oriental tradition may be represented by the translation of the tanden (now better known as dantien) as the "cinnabar field", which is situated "two inches below the navel" (Ahn 2008) and represents the centre of gravity of the human body. The discussion of this topic is limited to some hints functional for the general discussion. For the details, the reader is referred to Pérez-Arantegui (2021) in this TC.
Other "particular" findings and occurrences are also reported in the last section of this brief roundup on cinnabar occurrences (namely, "A (very) shortlist of other particular findings and occurrences of cinnabar").
An indispensable premise for the following sections concerns the bibliographic collection. Firstly, the publications collected are limited (almost always) to those in which the authors identified cinnabar through analytical techniques. Secondly, I am sure many publications were overlooked for various reasons ranging from accession difficulties to the language in which they were written. Consequently, the collection presented is not exhaustive but may offer a sufficiently articulated panorama of the state-of-the-art of the studies. The literature search was carried out by setting "cinnabar" as the key term in the search field (title and abstract) of Scopus. Eastaugh et al. (2004) and Siddall (2018) are also recommended on the uses of cinnabar and its characteristics.
Funerary use: esoteric power, social selfrepresentation and archaeological evidence The wide occurrence of Hg-based compounds in funerary contexts has long attracted the interest of researchers. Already in 1927, Peabody compiled a list of numerous occurrences in which "red paint" could be associated with the direct or indirect colouring (transfer from the burial) of the bones (Peabody 1927). He foc u s e d h i s r e v i e w o n o c h r e s a t a t i m e w h e n archaeometric analyses were not yet performed. Therefore, the achieved conclusion is also of interest for cinnabar: "We have seen that the use of color, especially red, in mortuary ceremonies is practically universal in time and space over the earth among prehistoric and primitive peoples". Peabody wondered, "what is the meaning of red?" and, after having warned the reader that "color symbolian is anything but obvious", came to the conclusion that "the most obvious suggestion of red is blood" (thesis argued and expanded in the following lines of his text).
Several authors have returned to this concept in the following years and the debate has opened numerous hypotheses and reconstructions. The common opinion is still focused on the correlation between red colour and blood and, consequently, the symbolism of life, death and sacrifice. In this regard, one of the anonymous reviewers rightly invites me to recall a concept dear to ancient philosophy, such as the "cosmic sympatheia". According to this Stoic thought, all beings on earth and in the heavens are closely connected 3 . However, other aspects such as the preservative properties of cinnabar, its use for body painting and tattooing and its magical aura are equally interesting and must be considered.
As for the conservative properties, cinnabar can delay the decomposition of the body thanks to its powerful bactericide and insecticide properties (Martín-Gil et al. 1995;Cervini-Silva et al. 2013). This intent is usually highlighted by the location of burials in underground environments and/or far from sunlight and humidity. In this case, its use would have been functional rather than symbolic; consequently, determining whether cinnabar was applied soon after death or after decomposition of the soft tissues can undoubtedly be of crucial importance (see also Domingo Sanz and Chieli 2021in this TC).
As for its use for body painting and tattooing, the discussion becomes more complicated and intriguing. In this case, the use of cinnabar may directly connect the deceased to her/ his life. Body painting could probably have had both an aesthetic and a social self-representation purpose during life. This practice would have followed a social dynamic that does not seem so distant from today's reality (with 60 million tattooed in Europe and more than 20% in the USA. Percentage considerably reduced in those countries like Japan where it is considered a social stigma -Harris Poll).
In this regard, the studies presented by Carter (2008) on EBI Cycladic society, Padilla et al. (2012) on argaric civilisation and Burger and Leikin (2018) on prehispanic Central Andean communities are exemplary. Carter (2008) connected the geographical and social expansion of the cultural and commercial exchanges of Early Bronze Age I Cycladic society (late 4 th -3 rd millennium BC) with a new way or a renewed interest in personal adornment (from tattooing to hair removal and jewellery). Quoting the authors, cinnabar "may have been reserved for special occasions (and people), limited body decoration and tattooing", thus "embodying" the ongoing political change. To support this intriguing hypothesis further, Carter also recalled the votive use testified by red-painted marble figurines and vessels found in Early Cycladic burials (references therein). Padilla et al. (2012) observed that the diffusion of cinnabar in Argaric funerary contexts was more widespread among female individuals than in males and, therefore, deduce that cinnabar was linked to face and body makeup. Burger and Leikin (2018) underlined that the prehispanic Central Andean communities used cinnabar for facial and body paint and its use went far beyond a vain desire for beauty to become an "expression of social identity" (Burger and Leikin 2018).
Observing the use in life for both beautification and social self-representation, it follows that the use after death (for the painting of human bodies) may achieve multiple values, from the desire to preserve one's natural appearance for the afterlife world to the desire to externalise one's social rank also through one's own burial or even, more simply, to give the deceased the appearance of a leaving body for the benefit of the living.
Even the magical aura to which cinnabar was likely associated could have played a role in all this. Still, several distinctions would become necessary as it is not obvious to assign a unique meaning to a pigment that has gone through very different cultures and chronological periods. Finally, it is good to include among all these likely hypotheses the possibility that the bodies of the deceased and the offerings were sprinkled with cinnabar to keep thieves and profaners away. The poisonous nature of the pigment was already well known in ancient times. This aspect may have represented both an intended use and an added value of cinnabar compared to red ochre.
Other aspects concern analytic practice more closely, such as assessing whether mercury entered bones either biogenically or diagenetically. In the former case, mercury derives from direct exposure; while in the latter, the process involves a transfer from the soil. On this topic, the research conducted by (a) Emslie et al. (2015Emslie et al. ( , 2019 on skeletal material from Middle and Late Neolithic and Early Bronze Age Iberian and Portuguese necropolis and (b) Cervini-Silva et al. (2013, 2018 on Mexican Red Queens and other funerary contexts must indeed be cited for both their intrinsic and methodological value. As anticipated above, a significant body of literature exists on the contamination of land and rivers following mining activities and valuable information can also be drawn from these publications. In this regard, two case studies clearly explain how complicated or controversial it may be to correctly interpret the presence of mercury/cinnabar in archaeological sites. The first case regards the mobilisation of cinnabar during diagenesis. This naturally occurring phenomenon has been recognised by García-Alix et al. (2013) as the alteration process responsible for the red colour of Miocene fossil mammals (bones and teeth) found in the Otura section (Granada Basin, Spain).
The second case regards the black mercury alteration detected on the surface of numerous jades found in "high-grade" Chinese tombs. This alteration has been recognised as a human-related phenomenon by Bao et al. (2019), who found that the alteration was due to the fire ("Liaoji") ceremonial activity (burning oblations) during which the jade was placed over cinnabar. The latter turned into mercury vapour (> 800°C) and thus caused the superficial alteration of jade.
As for the occurrences of cinnabar in burial contexts, the attestations are many; however, the archaeological findings are not accompanied by archaeometric analyses in many cases. Therefore, it is not always possible to know whether it is ochre or cinnabar or a mixture of both or if there are associated aromatic compounds. Here, only a few verified examples are presented to show the spread of this practice broadly. The number of studies performed on this topic also appears unbalanced as most refer to Spanish, Portuguese and South American archaeological sites.
The occurrences in Spain are listed in Table 2 and shown in Fig. 6. Those reported in Meso-and South America (Belize, Chile, Guatemala, Honduras, Mexico and Peru) are provided in Table 3 and shown in Fig. 7.
In Meso-and South America, the occurrences are mainly concentrated in the Mayan territory and scholars partially agree in stating that cinnabar was used above all in the funerary contexts of the ruling elite (Schele and Mathews 1999;Vázquez de Ágredos Pascual 2007, 2018Fitzsimmons 2009;Quintana et al. 2015). A comprehensive work on the use of cinnabar and other pigments for body paint is provided in the recent volume edited by Vázquez De Ágredos Pascual and Dupey García (2018), in particular, by Vázquez De Ágredos Pascual (2018) within the volume. The numerous contributing authors examined the phenomenon from all its points of view (material and cultural) and in the various social and cultural contexts of Mesoamerica, from pre-Columbian to modern times.
Apart from these two large areas that have returned most of the evidence (or in which the researchers carried out the highest number of archaeometric investigations), we must finally also remember the few occurrences around the Mediterranean basin: -Israel -On the 9 th millennium BC (Pre-Pottery Neolithic B) plastered skull of the KHH-Homo 8 from Kfar HaHoresh (Goren et al. 2001; Goring-Morris and Horwitz 2007 for an insight on the site); -Syria -On the painted Pre-Pottery Neolithic B skull inv.
No. 73.2772 found at Tell Abu Hureyra (Trench A, level 212) (Molleson et al. 1992); -Turkey -In the 8 th millennium BC phase of Çatal Hüyük, where cinnabar was used to paint the skull of a "woman with a necklace of sliced dentalium beads" and for wall paintings (Mellaart 1967); -Russia -In the 34 th -30 th century BC burial 1 (individual 1) at the Maikop-Novosvobodnaya settlement of Chekon-2 (Taman Peninsula), cinnabar was found in the fragments of the upper cranial vault (Korenevskiy et al. 2015).
To conclude, it is also worth underlining that the use of cinnabar in burials is also attested in prehistoric and historical China and Japan (Bao et al. 2019;Liu 2004).
In China, a comprehensive study on textiles and cinnabar decorated leather objects (1 st millennium BC-1 st /3 rd century AD) associated with mummies from the Xinjiang Uyghur Autonomous Region was performed by Kramell et al. (2016). The leather scabbard of a bronze sword covered by cinnabar was also found in the tomb M4 of the Qiaojiayuan site (Yun country, Hubei province; Luo et al. 2011).
Another example is represented by the cinnabar powder covering the surface of a set of the mid-11 th -mid-9 th century BC jade artefacts related to burial ceremonies from a tomb of the Ying State's Cemetery (Pingdingshan, Henan; Zhao et al. 2014). Particular use is also testified by the Shang epoch (1766-1122 BC) oracle bones (turtles plastrons and bovine scapulas used in divination) painted with cinnabar from Yin Hsü (Anyang, Honan;Benedetti-Pichler 1937).
In Japan, the funerary use of cinnabar lasted from the mid-Yayoi period till the late Kofun period (4 th century BC-6 th century AD). It was aimed at decorating (coffins), preserving (antisepsis) and staining (textiles), as well as having a ritual function and representing a symbol of power (Kawano et al. 2014). An example is provided by the Takamatsuzuka tumulus (7 th -8 th centuries) at Asuka (Nara prefecture, Kinki region), where cinnabar was identified in the murals (Kitada et al. 2015).
As a very last example, it is also worth mentioning the cinnabar painted skull found in Idaho that, dated to 600-700 years BP, was assessed to belong to one of four major Native American mitochondrial DNA lineages (Watkins et al. 2017).

Decorative use: cinnabar over time and space
Cinnabar was used for the decoration of mobile objects and probably later for the decoration of architectural surfaces. This trend seems valid both for the Mediterranean world and the Near East as well as for Meso-and South America. The most ancient attestations include mobile objects decorated with cinnabar found worldwide in funerary, religious and, to a lesser extent, residential contexts.
In South America, to give a representative example, the enormous number of 1500-1200 BC objects related to funerary practices and daily life found at Gramalote in Peru were painted with cinnabar or hematite or a mixture of both (Prieto et al. 2016).
In the Mediterranean area, particularly ancient attestations are sporadic. The likely oldest attestation on wall paintings dates to the level VIII (6700 cal. BC) onwards of the archaeological site of Çatalhöyük in Turkey (Çamurcuoğlu 2015). Out of a total of fifty-nine red pigment samples taken from wall paintings and burial contexts, the author found cinnabar in only 3 of them. Cinnabar was identified by Raman spectroscopy, either used alone or in mixture with red ochre, and was tentatively traced back to the mercury deposits "in the southwest and north of Konya region as well as around Niğde in the east". Mellaart (1967) hypothesised a provenance Table 2 Cinnabar in funerary contexts in Spain and Portugal (the numbers in the second column refer to Fig. 6) Spain 1. 5300-5000 cal BC Cova de l'Or (Beniarrés, Alicante). Cinnabar was found as a fine and pure red powder inside a Glycymeris sp. shell. Roldán et al. 2008;Domingo et al. 2012 2. Early Neolithic (likely between 5300 and 5200 cal BC) flint mine of Casa Montero. A thin cover of cinnabar was found on a flint blade. Hunt et al. 2011 3. Fifth millennium BC dolmen de Alberite (Villamartín, Cádiz). Finely chrushed cinnabar (silt and clay as prevailing fractions) mixed with hematite was covering bony remains and structural elements, also forming a~10-cm-thick layer in a portion of the gallery's floor.
Interestingly, this was the only use that was made of cinnabar onsite while hematite was used for the decoration of the structural elements. The authors also draw a correlation between the use of light-reflecting materials such as cinnabar, amber, quartz and gold and lighting that was to play an important role in the ceremonial. 7. Neolithic (3000 BC) dolmenic burial of "La Velilla" (Osorno, Palencia). Hundreds of pure and finely grained kilograms of cinnabar were covering human bones. Martín-Gil et al. 1995 8. Cueva de los Murciélagos (Cordoba). Cinnabar was found in a Neolithic container. Barrios et al. 1999;Martínez-Fernández et al. 1999 9. Montelirio megalithic tomb within the Valencina de la Concepción settlement (Copper Age, early 3 rd millennium BC). Cinnabar of likely Almadén provenance was mixed with minor iron oxides contents and spread over human bones, ivory and pottery along with coating a large slate slabs that formed the walls of the mortuary chambers.  Rocha et al. 2018 from the Sizma deposits but no supporting archaeometric investigations are available in this regard (Doherty 2011). In any case, the Sızma deposit (not reported in the Mindat.org database) is about 60 km away as the crow flies from Çatalhöyük and it is, therefore, the closest deposit known so far (Fig. 8).
The Vinča settlement provides another example. Cinnabar appeared ubiquitous in layers dated from the mid-6 th to the mid-5 th millennium BC (Vasić 1932(Vasić -1936, I as quoted by Gajić-Kvaščev et al. 2012). A cinnabar powder was also stored inside Neolithic pottery (inventory no. C-417, dated to 5200-4200 BC) (Mioč et al. 2004). Similarly, at Pločnik, a Gradac sub-phase ceramic vessel (end of the 6 th -early 5 th millennium BC) was found to contain a cinnabar powder (cinnabar mixed with quartz, illite, kaolinite and other clay minerals); moreover, cinnabar was also used to decorate figurines (Gajić-Kvaščev et al. 2012).
In the 1 st millennium BC, ancient examples (based on archaeometric evidence) are present on ceramic pottery and sculptures from Spain, Italy and Greece. As for ceramic decoration, it is possible to mention: Regarding sculpture, the Early Cycladic II (3100-2400 BC) marble figurines (Hendrix 1998; Carter 2008) provide a representative example.
Moving forward in time, cinnabar has been frequently used for the decoration of numerous Egyptian coffins. The cartonnages dated between the 21 st and the 25 th Dynasty (1070-525 BC) show a somewhat standardised palette with slight variations. Six basic pigments are constantly found: cinnabar, Egyptian blue, yellow and red ochres, orpiment and carbon black. Other copper-based pigments such as atacamite have been found less frequently; conversely, the presence of azurite, Prussian blue and lead white are generally attributed to retouches and restorations of a later period. The study performed by Gard et al. (2020aGard et al. ( , 2020b on a Ptolemaic cartonnage (305-30 BC) deserves a special mention because-besides the typical pigments-pararealgar, bonazziite and/or alacránite, uzonite and Egyptian green ((Cu,Ca)SiO 3 ) were also found (for the As-containing phases  Table 2 Table 3 Cinnabar in funerary contexts -Meso and South America (the numbers in the second column refer to 7. In the Classic Period (250-900 AD) burials of Toniná.

Fitzsimmons 2009
8. At the Olmec site of La Venta, cinnabar was found on human bones and among some offerings (e.g., on figurines), together with basalt, asphalt and salt.

Pool 2007
Belize 9. A late 9 th or early 10 th century offering consisting of 19g of cinnabar and 100g of hematite, along with other objects (jade, shell and pearl), were found at the Lamanai archaeological site in Belize (central Maya lowland) attesting the use of cinnabar for cerminial activity.
Pendergast 1982 Guatemala 10. At Kaminaljuyu, cinnabar was found amoung the offerings of several tombs (A-V. A-VI, B-I and B-III) covering jade (frequently found in Spondylus shells) and/or sting-ray spines. In this site, cinnabar was also used to paint miniature vessels as well as on a pyrite encrusted plaque, a cilindrical trypod with plano-relief carvings filled by cinnabar, a pair of thin orange jars, and a textile-impressed effigy. Cinnabar was sometimes mixed with calcite or diatomaceous earths and liquid mercury was also found. Kidder et al. 1946 11. At the underwater site of Contreras Alto -Los Jicaqnes (in the Lake Amatitlan), fragments of cinnabar and graphite were found together with about 400 fragments of jade ear-spools. Borhegyi 1959 12. At the archaeological site of Rio Azul, the men in the tombs 19 and 23 were covered by cinnabar. Carlsen 1986Carlsen , 1987 13. At the Early Classic (250-550 AD) archaeological complex of El Diablo (San Miguel La Palotada Biotope in the Municipio of San José, Department El Petén), in the Royal Maya Tomb of El Zotz where cinnabar (and hematite) was found on human bones and in (spondylus) shells. Cheung et al. 2013 14. In the Classic Period (250-900 AD) tomb burials of Tikal and those interred in the ancient city of Sacul. Honduras 15. At Copán, in the excavation of the mound in centre of the Plaza, a pot containing cinnabar powder and bones covered by cinnabar were found (1) . At the same site, bones painted by cinnabar has been found in several tombs: the 400-450 AD Hulan tomb of the Copán founder K'inich Yax K'uk' Mo'; the Margarita tomb (burial 93-2), presumably the wife of the previous, the mid-6 th century burial 92-3 and the~450 AD disarticulated burial 92-1. Other and/or same occurrences are reported in Gorokhovich et al. (2020). Maudslay 1889Maudslay -1902Schele and Mathews 1999;Sharer et al. 1999;Sedat and López 2004;Bell et al. 2004;Ashmore 2015 Peru (2) 16. In the necropolis of Ancón, cinnabar was found on one 11 th -13 th century AD mummy's hair.

Degano and Colombini 2009
Chile 17. In the 1399-1475 AD burial of two girls at Cerro Esmeralda (close to Iquique) likely testifying an Inca capacocha, i.e. a human sacrifice, cinnabar was found on the mantos (textile) of one of the mummies. Arriaza et al. 2018 (1) "In the centre of the mound, about 6 feet from the top, an earthern pot (Plate XXL, a) was found containing a bead-shaped piece of greenstone, pierced, diameter two and three quarter inches (b), the jade whorl of a spindle (c), the remains of a necklace of nine jade beads (d), four pearls (e), some small rough figures and other ornaments cut out of pearl oyster-shell (f), and other irregular pieces of roughly carved pearl-shell (g). At the bottom of the pot was some red powder (which proved to be finely ground cinnabar), and several ounces of quicksilver. Eighteen inches above this pot some traces of bone were found mixed with sand. At the level of the ground, more traces of bones were found mixed with red cinnabar powder and sand, and one large pierced bead-shaped stone, diameter three inches (h). About eight to nine feet below the level of the plain, a skeleton of a jaguar was found lying under a layer of charcoal." Further occurrences in Peruvian pre-Hispanic period are also reported in Burger et al. (2016). and the Egyptian blue and green pigments see Švarcová et al. 2021, respectively in this TC). Going further in time, the evidence of pictorial decorations on architectural elements begins to take on consistency. The fragments of decorated walls, floors and columns recovered in Persepolis and Pasargadae (6 th -4 th century BC), the wall paintings of the Tomb IV in Phoinikas in Greece (end of 5 th -4 th century BC; Avlonitou 2016), the second tomb of Vergina in Greece (4 th century BC; Filippakis et al. 1979), the Etruscan 'Tomba dell'Orco' at Tarquinia in central Italy (4 th century BC; Sodo et al. 2008) and, probably also the first Pompeian style House in Pella (400-168 BC; Calamiotou et al. 1983) are among the earliest attestations. However, it will be necessary to wait until the 2 nd and 1 st century BC before finding cinnabar constantly used to decorate architectural elements (based on sure evidence verified through archaeometric analyses).
Between the 3 rd and 1 st centuries, verified evidence testifies the use of cinnabar on both mobile objects and wall paintings in Europe and Asia. In the first case, some examples are found:   Table 3. Sites 14a and 14b correspond to Tikal and Sacul, respectively. Site 5-6 indicates the location of Dzibanché The numerous bowls containing powdered pigments found in Pompeii and analysed by Aliatis et al. (2010) must also be referred to an unspecified time before 79 AD.
Up to this period, the association with inorganic pigments is limited to carbon black and sporadically to madder lake while animal glue prevails among the binders. Other organic pigments such as indigo and other binders such as oils will be more frequent in the following centuries.
Between the 1 st and 3 rd centuries, the testimonies relating to the wall paintings gradually increase. However, most of the investigations are relevant to Italian archaeological areas: Other case studies regard wall paintings found in Morocco (Thamusida, 1 st -3 rd centuries by Gliozzo et al. 2012), Switzerland (Gallo-Roman villa at Dietikon, 1 st -3 rd centuries by Béarat 1996) and Turkey (Sinop Balatlar Church Complex, 2 nd -4 th centuries, by Bakiler et al. 2016).
In Egypt, most findings relate to paintings on wood. In this regard, famous examples are represented by the Roman mummy portraits of approximately the 2 nd century found at Tebtunis and investigated by Salvant et al. (2018).
From about the 4 th century up to the Middle Ages, the evidence relating to manuscripts (see Burgio 2021 in this TC), scroll painting and, overall, to painting on parchment, paper and various types of textiles is added to mobile objects (Table 4). In this regard, it is worth adding that, in manuscripts, cinnabar was used both for illuminations and as ink (see also above).
Among mobile objects, I have not found any evidence of possible use in ceramic decoration. On the contrary, I have collected numerous attestations relating to the sculptural decoration and, above all for the clay or sandstone sculptures of Buddha present in many Chinese regions such as Sichuan  Chongqing (late 12 th -mid 13 th centuries, retouched until the 1850s -Dazu Rock Carvings; Li et al. 2020b).
Among proper mobile objects, there are also three uncommon finds. In chronological order, the first is represented by the early 11 th -century beeswax seals from the documents of the Order of St. John of Jerusalem, sc. Knights of Malta (National Library of Malta, Valetta) investigated by Szczepanowska and Fitzhugh (1999). The second concerns the late 12 th -early 13 th century Lewis chessmen in ivory preserved in the Collection of the National Museums Scotland and investigated by Tate et al. (2012). The third ones are the 14 th -15 th century alabaster panels produced in the Midlands (UK) and analysed by Mounier et al. (2020) and Pereira-Pardo et al. (2019).
As far as architectural elements are concerned, the attestations are many and geographically widely distributed. The list provided in Table 5 shows that (a) the a fresco and the a secco techniques continue to be attested, although the authors frequently specify that some pigments as cinnabar were applied over an ochre layer ( Fig. 9C-D) or on dried lime; (b) the evidence is not chronologically continuous. The gaps recorded for the 5 th and 8 th -9 th centuries may be due to the lack of archaeometric studies on wall paintings of that time, or a lack in the bibliographic collection, or an actual decrease in the use of cinnabar in these periods.
Another interesting aspect is that at least until the 4 th century, the use of cinnabar remained for the realisation of mosaics' sinopias. In fact, to the 2 nd -1 st century BC examples found in the house below the Santa Susanna church in Rome (Boschetti et al. 2008), it is possible to add the 4 th -century sinopia found under the mosaic of the villa of Lod in Israel (Piovesan et al. 2014; wall paintings of the villa of Lod in Piovesan et al. 2016).
Lastly, it is worth mentioning the copious use of cinnabar for the decoration of icons. The examples are concentrated between the 13 th and 19 th centuries and are almost always prepared with the tempera technique ( Table 6).
As for Meso and South America, apart from the wide use of cinnabar to paint human bones and funerary/ceremonial practices, the attestations regarding the decoration of mobile objects and wall paintings gradually increase. In the first case, the objects are still primarily linked to the funerary sphere; in the second case, painted walls are concentrated in tombs and monumental complexes. The documentation appears still scarce regarding residential buildings.
To give just some examples, evidence of the use of cinnabar for the decoration of mobile objects has been provided for: As for wall paintings, based on Magaloni et al. (1993), Magaloni 1998and Vázquez de Ágredos Pascual (2007), "the earliest use of cinnabar in Mayan wall painting is documented at Bonampak, around the mid Late Classical period" (i.e. 250 and 900 AD). However, further research may lead to identifying this pigment in more ancient Classic contexts (i.e. Early Classic or Late Preclassic).
The testimonies are limited in number for the most ancient periods while they increase in the following centuries. Apart   Burgio et al. 1999 from the previously mentioned findings of Bonampak, the testimonies mainly regard the following sites:

Cinnabar for ceramic lustre
The lustre (or better "reduced-pigment lustre") is a particular decoration with a metallic sheen (coppery, golden or silvery) and iridescent colours (yellow, amber, ruby red, brown, green, blue, violet), used in Medieval and Renaissance times for the decoration of ceramics (Caiger Smith 1985;Mason 2004 Smith 1985;Fermo 2003a, 2003b;Hess 2004). Each region developed its own recipes and procedures so much so that the final products differ in decoration and visual appearance. For example, metal reflectivity is a characteristic of Spanish products not found in Syrian or Egyptian lustre . At a smaller scale, Deruta and Gubbio (at 43 km as the crow flies) developed two different styles, respectively characterised by "a copper-oxide luster and a brassy, straw-colored sheen" and a "silver-oxide luster and a more golden reddish gloss" (Hess 2004).
As reported in the literature, several recipes were handed down by several authors such as:    Other ancient recipes were also found in other types of documents, such as those reporting the recipe of Jacinto Causada from Alcora (1765), the Ordinaciones de la Cofradía y Gremio de Alfareros y Vajilleros (Ordinances of the Fraternity and Guild of Potters) and a formal request emitted by the chief magistrate of Valencia in 1785 (Pérez-Arantegui and Pardos 2008). In this regard, also the distinction made by Caiger Smith (1985) between passive and active recipes is worth mentioning considering that the active ones are those using cinnabar.
All these recipes are discussed in detail by Pérez-Arantegui and Pardos (2008) and reported in Fermo (2003a, 2003b), Pradell et al. (2004) and Roqué et al. (2008) to which the reader is referred for details. Here, it is interesting to note that only the treatises at points 1, 4, 5 and 6 and the  Stojanović et al. 2015 recipe of Jacinto Causada inform about the use of cinnabar. Therefore, its use is to be considered widespread but not mandatory to produce lustre. The numerous archaeometric analyses allow the main characterising feature of lustre to be described as a few hundred nanometres thick layer, including silver and/or copper nanocrystals dispersed in a glassy matrix.
The production required three firings: (1) firing of the biscuit at about 900-1000°C; (2) glazing (likely by immersion) and subsequent firing; (3) painting of the lustre decoration (dissolved in vinegar) and subsequent firing in a 480-600°C temperature range and a reducing atmosphere (but not fully reducing, see Molera et al. 2007), able to reduce Cu and/or Ag compounds into the metal state.
The materials used and the procedures adopted in the three phases all affect the final appearance of lustre and characterise specific products. For example, among all possible types of glazes, (a) the tin-opacified lead-alkali were the preferred ones (Tite et al. 1998), (b) lead-containing glazes were necessary to obtain a metal-like reflectivity ) and (c) the Italian glazes were often characterised by higher Na 2 O contents than those measured in Spanish products (Padeletti and Fermo 2003a).
Among the key factors responsible for the appearance of the end product, it is possible to enlist: the (nanometric) dimension, composition and distribution of the particles (for iridescent metallic sheen), the firing and annealing temperatures (influencing the size of the final particles), the atmosphere conditions (influencing the reduction of Cu and Ag compounds), and the relative ratio of Cu and Ag and their absolute amounts (for colour variations).
These milestone papers represent the essential starting point for tackling a study of lustre and I, therefore, refer to these authors for the necessary insights. Here, I will focus on why cinnabar was used, although it decomposes completely during firing and, therefore, there is no trace of it in the finished products.
Experimental archaeometry performed by Pradell et al. (2004Pradell et al. ( , 2008b, Cepriá et al. (2007), Molera et al. (2007) and Roqué et al. (2008) has clearly shown that the presence of cinnabar is relevant during firing rather than in the characteristics of the final product.
The decomposition of metacinnabar creates a sulphoreducing atmosphere that reduces tenorite (CuO) to cuprite (Cu 2 O). In a temperature range between 400 and 600°C, the released sulphur forms copper and silver sulphite (e.g., Ag 2 SO 3 ), sulphate and sulphide (e.g., CuSO 4 , Ag 2 S, 3Ag 2 S· Ag 2 SO 4 ) that prevent the alloying of Ag with Cu while mercury vapours ensure that silver compounds are not reduced to metallic silver before entering the glaze.
Undoubtedly, lustre production implies a delicate process in each phase and accidents may occur along the way. For example, the formation of Ag-Hg compounds such as luanheite (Ag 3 Hg) can inhibit the formation of metallic silver. Furthermore, it has been proved by voltammetry of immobilised microparticles (VMP) studies that both iron and cinnabar promote the reduction of Ag and Cu, provided that only Ag or only Cu are present. When both Cu and Ag are present, the reduction process of Ag is made more difficult (Cepriá et al. 2007). Consequently, the role of cinnabar varies with the variation of the present quantities of Cu and Ag because it triggers different chemical processes, induces a variation in the temperatures at which the processes take place and, inevitably, leads to products with distinct characteristics.
Despite evidence mainly obtained on Hispano-Moresque pottery, further studies on Italian lustre have also suggested the use of cinnabar as a pigment in ruby red lustres from Gubbio (Padeletti and Fermo 2004) Among the archaeometrically investigated lustre productions, the use of cinnabar has been assessed for both Hispano-Moresque (13 th century Les Olleries Xiques workshop at Paterna, Valencia, Spain; Molera et al. 2001) and Italian lustres (15 th -17 th century majolicas from Gubbio; Padeletti and Fermo 2004); however, the quantification of Hg is not a common routine.

Cinnabar in lacquered objects
The lacquer is a natural resin chiefly composed of catechol derivatives that "polymerizes by the oxidation of urushiol with catalysts of laccase during the drying process" . The composition of the lacquers varies according to the tree from which the sap is extracted, and, on this basis, it is possible to draw meaningful geographical distinctions: the Rhus vernifera grows in China, Japan and Korea and urushiol is the characteristic component of the lacquer it produces; the Rhus succedanea grows in Vietnam and Taiwan (Formosa) and laccol characterises the composition of this lacquer; the Melanorrhoea usitate grows in Laos, Myanmar, Tailand and Cambodia and thitsiol identifies its lacquer.
Lacquerware has been and still is popular throughout Asia. It has been used for multiple purposes, ranging from the decoration of objects such as tableware and furniture to the decoration of inscribed plaques, jewellery and coffins.
Indian, Burmese, Thai and Japanese and, finally, European decorations are well known. The production period probably begins in the Stone Age and reaches up to the present day. The oldest examples are likely represented by Japanese (e.g., the Stone Age arrowheads; see Niimura et al. 1999 and references therein) and Chinese objects (see below). Vietnamese products also include particularly ancient lacquer decorations, dated to the Dong Son culture (i.e. more than 2000 years ago) (Naziree 2013). Conversely, Burmese lacquer-the socalled thitsi-appears chronologically later basing on archaeological evidence. Nevertheless, Tamburini et al.
(2019) pointed out that it "has probably been used for more than a millennium".
Unfortunately, most of the studies concerning Asian lacquers did not concern the pigment palette identification; therefore, the archaeometric case studies reporting on cinnabar use are few and mainly concern Chinese products.
In China, the oldest examples date back to the Chinese Neolithic age; however, the authors disagree on which is the oldest lacquered object found so far. Based on Ma et al. (2017), the oldest example is represented by a black lacquered bowl dated to 8000 years BP, found at Kuahuqiao (Xiaoshan, Zhejiang). Based on Li et al. (2009) and Wang et al. (2018), the oldest example is represented by the cinnabar-containing lacquer-painted wood bowl found at the Hemudu site (Yu-yao, Zhejiang) and dated to more than 7000 years BP. Li et al. (2009) also propose a map of the lacquerware distribution between the Qin (5000-206 BC) and the Han (206 BC-220 AD) Dynasties.
Starting from the Tang Dynasty (618-907 CE), it is possible to follow the development of the "carved lacquer", which reached its peak in the Qianlong Period (1736-1796 CE) and was particularly popular until the Qing Dynasty (1636-1912 CE) (Wang et al. 2018). This technique has its basic raw material in lacquer and consists of obtaining the decoration by carving a thick lacquer layer. Among the colours of carved lacquered objects (red, yellow, green and black or polychrome), the red one was the favoured and cinnabar was the preferred colouring pigment used to prepare it.
Archaeometric studies were conducted on various types of Chinese objects and provided comparable results. the lacquer ash layer (9 stucco layers and 10 fibres layers; the so-called wan lacquering technique) and (c) the lacquer film pigment layer, mostly consisting of organic materials (lacquer sap from Rhus vernicifera ➔ urushiol, animal gelatin, drying oil and proteinaceous materials) and four layers of inorganic pigments: calcite, carbon black, cinnabar and gold (the so-called Jin Jiao technique, i.e., the technique applied to mix pigments and lacquer and "painting lacquer above the gold technique"). & In a birthday inscribed lacquer plaque (1866 AD), Zheng et al. (2020) found a primer lacquer layer made of calcite, cinnabar, minium and Chinese lacquer, followed by a second plaster lacquer layer made of gypsum and Chinese lacquer and a third and last layer made of Chinese lacquer.
Aside from China, a few examples of cinnabar-lacquered objects from the Japanese and Vietnamese areas have been analysed by Colomban and Mancini (2013) and Kamiya et al. (2015). Burmese lacquered objects kept at the British Museum in London (UK) have been the object of the archaeometric study performed by Tamburini et al. (2019).
In Europe, lacquerware began to be imported in the mid-16 th century. Around the late 17 th century, the practice of combining local furniture with lacquered Asian panels spread throughout Europe. The example presented by Bösiger (2019) well testifies this practice and the advent of French lacquer. The history of the red lacquered chest of drawers (18 th -20 th centuries), presumably realised by Charles Chevallier dit Le Jeune and François Rübestück 4 , has a long and complicated history that not even the many analyses were able to clarify fully. The only incontrovertible results concern (a) the use of cinnabar in the Chinese lacquer, (b) the use of minium in the French lacquer and (c) a reworking in the 20 th century confirmed by the presence of the red pigment PR3 (beta-naphtholtoluidine).
A special mention of the South American lacquers decorated with the technique called barniz de Pasto 5 is deemed necessary at this point. This technique uses a native South American resin named mopa mopa. This phenolic resin is obtained from the Elaeagia pastoensis 6 tree, which grows "in mountainous regions of western South America from Colombia to Ecuador" (Newman et al. 2015). Although initially used as an adhesive (for example, glue feathers to ceremonial plumes; see Gomezjurado Garzón 2008), its later use mainly included decorative purposes. Once soaked, heated, kneaded and masticated, the barnizadores spread in wide and thin sheets and coloured with the addition of mineral pigments (e.g., ochre) or animal (e.g., cochineal) and vegetable dyes (e.g., achiote-Bixa orellana) (Mora-Osejo 1977; Gomezjurado Garzón 2008). When a particular brilliance was sought, a layer of metal leaf typically silverwas "sandwiched between two layers of coloured and/or uncoloured Pasto varnish" (Portell 1992). Depending on the materials used and the technique, various types of barniz could be obtained (e.g., bright, matt and chinesco) to waterproof and decorate (carved) wooden surfaces of domestic or religious materials (Fig. 10). The analyses carried out on this type of object are very limited. Consequently, also the claims of cinnabar are numerically small and concentrated on the qeros, i.e. the typical Andean drinking vessels: on a series of Inka mopa mopa carved and painted wooden qeros, the most common pigment was cinnabar (Pearlstein et al. 2000); in the pink samples taken from three qeros dated to the Transitional Inka/Early Colonial period, cinnabar was found together with cristobalite, anatase and α-quartz 7 or with gypsum and anhydrite 8 (Howe et al. 2018); in Inka-Colonial qero cups kept in several Museums in the USA 9 (Newman and Derrick 2001); in an Inka qero excavated at Moqi (southern Peru), cinnabar and orpiment were used for the red and yellow inlays, respectively (Newman et al. 2015).
Regarding these mopa mopa objects, it is also interesting to note that not only cinnabar but also calomel has been found (see the following section on Calomel).
Lastly, it is also worth adding that the studies performed by Strahan and Tsukada (2016) revealed that cinnabar-containing lacquered objects emit small amounts of mercury vapour and may represent a source of contamination.

A (very) short list of other uncommon finds and occurrences of cinnabar (chronological order)
-The second century -Traces of cinnabar were found on stones deemed to have served as touchstones. Together with gold and silver weapons and vessels, these stones were found in the rich burial of two males aged 40 and 60, uncovered near the Roman army camp at Mušov (south Moravia, Czech Republic). In particular, the stone no. 12 bore traces of cinnabar as well as streaks of gold, silver, tin, lead and various types of gold and silver or gold, silver and copper alloys (Ježek et al. 2018). -The fifth-seventh centuries -Cinnabar has been found on textiles at Samdzong in Nepal. The archaeological context includes ten shaft tombs containing 105 individuals. The collection of textiles analysed by Gleba et al. (2016) were coloured with Indian lac, munjeet, turmeric and knotweed/indigo. Those coloured with cinnabar likely recall a technique (dyeing with mineral pigments) that "was well developed in China already during the Shang (1600-1046 BCE) and Zhou (1046-256 BCE) Dynasties" and whose products were intended for the elite (Gleba et al. 2016). -High Middle Ages -Cinnabar, mercury and antimony were used to produce counterfeits of natural bezoars. These last are masses, sometimes mixed with food, formed in the digestive tracts of some ruminants and humans. Introduced to Europe by the Crusaderstogether with unicorn hornsthey were believed to be magical antidotes against arsenic poisoning (Barroso 2013). -The sixteenth century -In the wreck of Gnalic various kinds of goods were found: glassy materials, semifinished metals, white lead in wooden barrels and cinnabar. The ship "Gagliana Grossa" set sail from Venice in the autumn of 1583 was headed for Constantinople (Auriemma 2018). -The eighteenth century -The frigate HMS Pandora was dispatched (1790) to intercept mutineers on the HMS Bounty. Returning from Tahiti (March 1791), it struck the Barrier Reef and sank. Cinnabar powder associated with keratotic material (e.g., collagen) was found in a chest found in an officer's cabin (Edwards et al. 2003).

Cinnabar procurement and trade
I warn the reader that while the investigations carried out on finished products are consistent, those relating to mines, processing and trade are much smaller. The discussion of the various topics is therefore limited and geographically unbalanced. In Europe, apart from the Almaden district's mines in Spain, the information on which mines were exploited in ancient times is still scarce or scattered in hardly accessible publications. Perhaps the exception is the case of the mines of Mt. Altai in Serbia, where the archaeological excavations brought to light several findings of great interest. Several authors claimed that the exploitation of the Šuplja Stena mine (Mt. Avala, Belgrade), was already running as early as the 4 th millennium BC (Jovanovic 1978;Shepherd 1980 reporting the opinion of Childe 1957). This statement is likely true also considering that, before 1968, it was the only mercury mine in the whole territory of Serbia (Gajić-Kvaščev et al. 2012). As for Spain, a map of the primary cinnabar deposits probably exploited since ancient times is provided by Domínguez-Bella (2010). Other isolated cases seem deduced more from cinnabar discovery in the neighbouring archaeological sites than from investigations aimed at verifying ancient exploitation. In other cases, the information is linked to modern exploitation. Therefore, one remains in doubt about when the exploitation began (e.g., Monte Amiata in Tuscany). In China and Japan, the Wanshan mine (Guizhou, China), the XunYang mine (Shaanxi, China), the Niu mine (Mie, Japan), Yamato-Suigin mine (Nara, Japan) and Sui mine (Tokushima, Japan) were identified as ancient mines (Kawano et al. 2014).
In Meso-and South America, the Peruvian-Ecuadorian case is perhaps the one that has received the greatest attention because a real controversy has arisen over the exploitation of cinnabar from Huancavelica (Peru) and that of Azogues (Cañar, Ecuador). As far as it is possible to reconstruct, the casus belli is represented by Truhan et al. (2005) paper. During an excursion to Loma Guaschon, they found cinnabar deposits already reported in previous documentation. After providing the reader with various information about the mining exploitation of some Ecuadorian, Colombian and Peruvian deposits, they hypothesised that "la productividad del cinabrio azogueño durante la temprana colonia fue de tal magnitud que la misma Fuente puede haber tenido importancia en las redes de intercambio precolombinas" 10 . Burger et al. (2016) responded by claiming the primacy of Huancavelica in prehispanic times. These authors argued about the correctness of the interpretation of the documents presented by Truhan et al. (2005) and strongly opposed the "Ecuadorian cinnabar hypothesis". For clarity, Burger et al. (2016) did not object that there was a trade network between Ecuador and Peru (witnessed by other types of goods such as spondylus, strombus and conus) as to the fact that cinnabar was part of these trades. Burger and coworkers seriously questioned the very existence of mercury mines in Azogues. They pointed out that cinnabar had not been unequivocally identified "in any prehispanic archaeological context or on any prehispanic object in an Ecuadorian museum or private collection". To further support their theory, they recalled the isotope (Hg) investigations obtained in 2003 (Cooke et al. 2013). The Hg-isotopic analyses were carried out on geological ores from Peru (Chonta and Huancavelica), Honduras (Jalaca), Colombia (Antioquia and Quindio), Bolivia (Cerro Colorado and Mina de Pedernal) and Chile (Algarrobo Mine) and on archaeological artefacts from Peruvian archaeological sites and/or referring to the Early Horizon and Late Intermediate period of Peruvian culture. The results assigned almost all archaeological finds to Huancavelica except for samples A15-A17, corresponding to three wooden digging boards from private collections (preserved at Metropolitan Museum of Art, New York and the National Museum of the American Indian, Washington, DC, USA). As for the latter, the authors stated that further analyses of raw materials were necessary to establish their provenance.
The answer was not long in coming. Bruhns et al. (2017) refuted the objections raised by Burger and co-authors on the documentation concerning the Azogues mines and replied with an indication that seemed fundamental to me: "". The quarrel continued but on closer inspection, this seems a case in which only archaeometry can write the ending. Indeed, while there is no archaeological evidence to support the "Ecuadorian cinnabar hypothesis", there is not even to discard it definitively.
Other studies are available for the exploitation of sources in Mexico and Honduras sources.
In Mexico, Manzanilla (2005) claimed that the Teotihuacans likely exploited the Sierra Gorda of Queretaro sources and, possibly, also those of San Luis Potosi in the Classical period (1 st -9 th centuries). Moreover, the ancient and modern exploitation of Queretaro mines has been the object of the study performed by Campos and Muñoz (2013) to map the archaeological sites and evaluate the Hg contamination issues from mining.
In Honduras, Gorokhovich et al. (2020) investigated the provenance of cinnabar found in the pre-Columbian site of Copan. They carried out a field survey that led them to detect the presence of mercury in the valley. However, they believed that the field was of such limited size/extension to make it more likely to import this material rather than exploiting the local sources (e.g., those present in the Quebrada Sesesmil watershed close to the settlement). On the other hand, they believe that future research in El Tablón mountain may instead be considered promising about the possible identification of cinnabar and Asbased pigments mines.

Production technology
Theophrastus informs us about the old way of producing cinnabar (De Lapidibus, 58-60) and indicates two types of cinnabar, one natural and one artificial.
In the first category, he included the cinnabar from Iberia (Ἰβηρίαν), very hard and stony, and that found in the Colchis (ἐν Κόλχοις), which was found on mountain cliffs and was brought down by shooting arrows.
In the second category, he included cinnabar coming only and exclusively (εξ ενός τόπου μόνον) from the region located just above Ephesus (ὑπὲρ Ἐφέσου). According to Theophrastus, a particular sand that shone like the scarlet dye (λαμπυρίζουσαν καθάπερ ὁ κόκκος; Kermes) was collected in this area. This sand was first pulverised in stone vessels until it reached the desired grain size and then washed by decanting in copper vessels. The worker then repeated the process until the achievement of the desired product. Theophrastus also added that workers' skills were essential in determining the amount of finished product (from nothing to much). The cinnabar remained at the bottom while the fraction remaining suspended in the washing water was used mainly for cosmetics.
The discovery of the procedure is attributed to Kallias, an Athenian involved in the activities of the silver mines (probably those of the Laurion) who, associating the shiny appearance of that sand with the presence of gold, would have collected and processed it, about 90 years before Praxiboulos was archon at Athens.
According to Theophrastus, this was the sign of how art imitates nature while producing its own substances. After a short digression, he describes the procedure for obtaining quicksilver (χυτὸν ἄργυρον): grinding cinnabar with a copper pestle together with vinegar in a copper mortar.
Since it is beyond the subject of this review, I will omit to discuss the production technology regarding quicksilver and the evident differences between the procedure handed down by Theophrastus and that reported by Dioscorides (De materia medica, 5, 94; through heating cinnabar). However, it is necessary to specify two critical aspects of the text of Theophrastus.
Firstly, the territory indicated with the term Iberia by Theophrastus and later disclosed as Hispania by Plinius (Naturalis Historia 3, 4, 30; 33, 38, 113-114) 11 , perhaps does not correspond to Spain as to the "eastern part of the present Transcaucasian Georgia" as pointed out by Caley and Richards (1956) and Rosół (2018). On the other hand, the possible error of Pliny is well understood in the 1 stcentury Roman world, that is when "the most famous cinnabar mine for the revenues of the Roman nation being that in the region of Sisapo in Baetica, no item being more carefully safeguarded: it is not allowed to smelt and refine the ore upon the spot, but as much as about 2000 pounds per annum is delivered to Rome in the crude state under seal, and is purified at Rome, the price in selling it being fixed by law established at 70 sesterces a pound, to prevent its going beyond limit. But it is adulterated in many ways, which is a source of plunder for the company" (Plinius, Naturalis Historia 33, 40, 118-119, translated by Rackham 1952).
Secondly, according to Theophilus (De diversis artibus, first half of the 12 th century) the second "factitious" type was not cinnabar but, likely, minium.
Soon after, Theophilus does not fail to describe "the method of making the best vermilion, 'Vermiculum optimum'" "If you wish to make the best vermilion, take a glass bottle and cover it with a lute outside; and take one part of quicksilver, by weight, and two, by weight, of white or yellow coloured sulphur. Put it into the above bottle, which you afterwards place on four stones, and, laying a very slight fire of coals round the bottle, cover its mouth with a tile, and when you see the smoke come white from the mouth of the bottle, close it, but when a smoke as red as the vermilion shall come out, take it from the fire and you will have the best vermilion. Similar recipes are found amongst the medical writers of the thirteenth and fourteenth century, but are mostly repetitions" (reported from Hendrie 1847).
Other recipes have been handed down in manuscripts such as the ancient Compositiones ad tingenda or "Lucca manuscript" (8 th -9 th centuries), the Mappae Clavicula (from the 9 th century) and the Bologna manuscript 2861 (15 th century).
"If you wish to make vermilion, take a glass flask and coat the outside with clay. Then take one part by weight of quicksilver and two of white or yellow sulphur and set the flask on three or four stones. Surround the flask with a charcoal fire, but a very slow one, and then cover the flask with a tiny tile. When you see that the smoke coming out of the mouth of the flask is straw-colored, cover it; and when yellow smoke comes out, cover it again; and when you see red smoke, like vermilion, coming out, then take away the fire, and you have excellent vermilion in the flask." (Mappae Clavicula, Chapter i. Vermilion; reported from Smith and Hawthorne 1974, p. 26) "The recipe for cinnabar. Take 2 parts of clean quicksilver and 1 part of native sulphur, and put them in a flask, and, cooking them without smoke and over a slow fire, make cinnabar. Wash it properly" (Mappae Clavicula corresponding to Lucca manuscript 223v.10; reported from Smith and Hawthorne 1974, no. 105, p. 42) "A recipe for cinnabar. A recipe for true, clean cinnabar. Take 2 parts of quicksilver and 1 part of native sulphur, and 1 part of clean urine. Take a very clean strong flask that will endure heat without smoke. Put into the flask the sulphur, ground and mixed with the quicksilver, 2 ounces short of filling it; but if it is a larger flask, it should be short 3 ounces. Mix and shake. Get ready a smaller glassworker's furnace, which should amply hold the flask, leaving a place where the flask may enter. Split reeds and with them light the furnace. Leave another window so that the flames may breathe out all round the flask. The sign of [completion of] the cooking is this: when you see that the flask has less purplish smoke and is making a color like cinnabar, stop adding fuel, for the flask gives a crashing sound from the great heat. When the cinnabar is thoroughly cooked leave it to cool." (Mappae Clavicula corresponding to Lucca manuscript 229.24; reported from Smith and Hawthorne 1974, no. 221C, p. 61) "M263. To make cinnabar. Take quicksilver and two parts of white or yellow sulfur. Incorporate the finely ground sulfur with quicksilver, put it in a bottle well luted with lutum sapientiae and let dry. Then put it on the fire over a low heat and cover the mouth of the vase with a tile. Cover and uncover it frequently. When you see the yellow smoke coming out, you will know it is nearly done; let it remain and keep the fire until the smoke becomes almost peacock red. At that point you take it off the heat and let it cool and so you will have fine cinnabar" 12 (Bologna Manuscript, very similar to Mappae Clavicula, Chapter i. Translated).
Ultimately, the ancient procedures to obtain cinnabar were all relatively simple. They started from raw materials that were already well recognisable and relatively pure. They then mixed a few ingredients and let the heat do the rest, just taking care to observe the colour of the fumes. Therefore, the process did not require particularly high temperatures or complex tools. Also, the lutum sapientiae was a compound typically used for distillation and its production required raw materials that were simple to find, such as strips of linen or wool, flour, egg white, ash, dung and clay (Biringuccio, De la pirotechnia, 1540).
The production of synthetic cinnabar, on the other hand, seems to derive from a subsequent technological development, probably transferred from Arabic (Gettens et al. 1972;Miguel et al. 2014) or Chinese (Gettens et al. 1972;Franquelo and Pérez-Rodríguez 2016) artisans.
The feasible processes are essentially two: the dry one and the wet one. Gettens et al. (1972) reported numerous manuscript sources which, starting from the 8 th century, describe the dry process and its subsequent modifications. It consists of producing black β-HgS and heating it until it turns red α-HgS.
Melo and Miguel (2010) and Miguel et al. (2014) reproduced one of the dry process recipes contained in "The book on how to make colours" and verified that the complete grinding of S with Hg produces black β-HgS. Based on the process described by Franquelo and Pérez-Rodríguez (2016), it would simply consist of stirring Hg with S and successively heating at 235°C. These last authors also discuss the possible addition of small amounts of Sn.
As for the wet process, Gettens et al. (1972) seems to lead it back to Gottfried Schulz based on Kopp 1843Kopp -1847. In 1867, Schulz would have discovered that metacinnabar heated in a solution of ammonium or potassium sulphide transforms into vermillion. From here, it would have resulted in a production destined to become the favourite in Germany and England.
For further information on production technology, the reader is referred to the aforementioned publications. Still, it may be helpful to add that these authors have also provided optical and microscopic images and descriptions to favour the discrimination of the three types of cinnabar (i.e. natural, obtained with the dry process and obtained with the wet process) without hiding the objective difficulties. The distinction between natural and artificial cinnabar is not simple. The presence of other phases to which cinnabar may be associated in the supply source (see the associations described in the first section) undoubtedly represents the first clue but may prove insufficient.
On this topic, Franquelo and Pérez-Rodríguez (2016) discussed how the presence of impurities, the size and morphology of grains could guide the determination of natural cinnabar (generally heterogeneous in size and shape irregular) from a synthetic one (presence of K, S and Sn). However, they also note objective difficulties in distinguishing natural cinnabar from that produced through the dry process.

Cinnabar application
This topic requires two critical aspects to be addressed separately: (1) cinnabar and the fresco technique and (2) cinnabar and organic materials.
The first point is well known: cinnabar is unsuitable for painting a fresco. This incompatibility has been known since ancient times but has not limited its use to decorate wall structures. Cinnabar is poorly soluble and therefore when it comes into contact with fresh plaster (i.e. not yet dried = opposite of secco), it reacts and transforms into black metacinnabar. To overcome this problem, it was common to apply a red ochre base a fresco and finish with cinnabar once the fresco had dried. According to fresco and lime-painting techniques, an example of the yield of cinnabar was experimentally made by Piovesan et al. (2012).
As for the second issue, the cinnabar interaction with ovalbumin and casein has been experimentally tested by Duce et al. (2012) in both unaged and aged tests. The authors observed that while cinnabar forms stable complexes with ovalbumin and promotes oxidation, it modifies the elution pattern of casein and promotes hydrolysis. The interactions with protein-based binders and fatty acid esters from egg yolk have also been investigated by Romero-Pastor et al. (2011b). They observed how the interaction of cinnabar with the protein causes a shift in the spectral region where the polyunsaturated fatty acid esters of the egg yolk appear. Further information is also provided in the study of the degradation processes involving several types of binders due to ultraviolet (UV) radiation and ageing by Ropret et al. (2007) and Romero-Pastor et al. (2012). The interaction with eastern and western drying oils was the object of the experimental study performed by Wang et al. (2015). These authors demonstrated that, compared to azurite, malachite and ochre, cinnabar is more effective in accelerating the ageing of drying oils and their hydrolysing process.

Cinnabar alteration
The colour variation of HgS has intrigued scholars from various fields so much that it has inspired fine philosophical discussions on the reproducibility of representations and empirical imagination in the Critique of Pure Reason by Kant (Westphal 1997).
As described above, the cinnabar (α-HgS) → metacinnabar (β-HgS) conversion implies that the colour changes from red to black and occurs above temperatures that may vary from 315 to 400°C depending on the surrounding conditions and the degree of purity of the mineral.
However, it is common knowledge that high temperatures are not strictly necessary to observe cinnabar's blackening on artworks. Therefore, numerous researchers studied the phenomenon more thoroughly to trace all the possible causes and discovered that metacinnabar formation is only one (rare) cause.
Firstly, McCormack (2000) highlighted that chlorine contents are decisive for cinnabar blackening. His research focused on natural deposits containing photosensitive cinnabar (generally associated with calomel, corderoite, terlinguaite and kleinite, eglestonite, comancheite, mosesite, radtkeite and kenshuite). The chemical analysis of some photosensitive cinnabar samples showed chlorine contents ranging from 0.04 to 0.96 wt%. This evidence led the author to conclude that the "darkening of cinnabar in sunlight is caused by the presence of contained chlorine or other halogens". Furthermore, McCormack ex perimentally observed th at n onphotosensitive cinnabar blackens to light when exposed to halogens. Spring and Grout (2002) used McCormack's conclusions to explain the visible blackening of some artworks. They realised that the sodium chloride in the dirt particles on paints could trigger the same reaction that, in nature, induces the vermilion → corderoite transformation. This, in turn, would have led to the formation of calomel + S + black HgS upon light exposure. However, Spring and Grout further highlighted how even the painting technique is a crucial factor in the pigment's discolouration. They observed that the alteration was more prominent where cinnabar was used alone while absent or lower when applied together with red lake or red lead.
A few years later, the study by Cotte et al. (2006) returned to this topic, focusing on Pompeian frescoes. Their investigations confirmed the heterogeneous nature of the degradation products and the possible coexistence of corderoite (ascertained by spectra XANES), terlinguaite, corderoite and calomel. The authors indicated Punic waxoften used to protect frescoes and produced using seawateras a possible chlorine source. However, they also add another possible path involving calcite sulphation, resembling the process at the origin of black crust formation.
Regarding Pompeian frescoes, the famous eruption of the Vesuvius and the corresponding temperature increase deserve further mention. Ballirano et al. (2013) observed that the conversion temperature of the Almadén samples they investigated (> 673K = 399.85°C) was higher than that fixed as the formation temperature of the pyroclastic deposits of Pompeii (653K = 379.85°C) and thus claimed that the blackening of Pompeian cinnabar also had to be due to impurities contained in the pigment.
What unites the work of Cotte et al. (2006) and that of Ballirano et al. (2013) is that while thinking of two different processes, both recognise the blackening of cinnabar as a process chiefly due to impurities, either naturally contained within it or brought from the outside.
On the other hand, the applied and experimental research carried out by Radepont et al. (2011Radepont et al. ( , 2015 confirmed that both light and chlorine presence are the key factors in the discolouration of pictorial surfaces. Their main results may be summarised as follows: (a) evaluation of the colour changes over time; (b) identification of degradation products such as calomel, corderoite, kenhsuite, terlinguaite and sulphates; (c) iInvestigation of the reaction sequence leading to calomel and corderoite formation (in the various layers).
In 2013, Nöller proposed a review on cinnabar where the darkening by radiation, the influence of substrates and the reactions with halogens, other pigments and binding media are summarised. The author reports numerous discolouration examples in artworks and highlights how natural cinnabar alters differently from the artificial vermilion, depending on structural impurities (Nöller 2013). While confirming the importance of the role played by light and chlorine, the experimental work carried out by Kegelman Neiman et al. (2015) also demonstrated that high relative humidity must be added to the factors responsible for colour variations. Furthermore, the formation of calomel in tests exposed to saline solution, with or without light exposure, combined with the absence of corderoite led to a revision of the previous assumptions on reaction mechanisms and, especially, on the catalyst role of chlorine ions (see Keune and Boon 2005). Lastly, Kegelman Neiman and coworkers observed that the presence of white calomel and the absence of black corderoite made it challenging to explain the colour variations observed during alteration and cautiously put forward some hypotheses, including that of the presence of metallic mercury.
Other works have been conducted on this topic but they left the big picture unchanged; if anything, more details were presented on specific issues such as pigment-binder interactions upon weathering (e.g., Elert and Cardell 2019). Lastly, the work done by Hogan and Da Pieve (2015) on the mechanisms involved in the darkening of cinnabar is worth mentioning because it clarifies the role of chlorine. For the weathering of a sample exposed to light and humidity, the authors proposed a process in 4 steps: (1) uptake of Cl on α-HgS surface; (2) consequent formation of γ-Hg 3 S 2 Cl 2 first and of the more stable cubic phase α-Hg 3 S 2 Cl 2 after; (3) structural instabilities cause the release of elemental Hg (0); (4) chloride phases form (over the degradation products previously formed) and undergo further degradation processes.
In a nutshell, (a) chlorine, light and humidity or, possibly, a considerable temperature rise induce the blackening of cinnabar, (b) none of the researches presented here found metacinnabar.
The bad news is that blackening appears to be a relatively simple process to happen and, for now being irreversible, we do not currently have the means to counter it.

Calomel
The presence of calomel in an artwork is generally referred to as a degradation process. Still, on this point, we need to clarify.
The Art of limning by Nicholas Hilliard (ca. 1537/1547-1619) is often quoted in this regard (Burgio et al. 2018;Crippa et al. 2020) because the author mentions a white mercury pigment recommended for limning: "ther is also an excelent whit to be made of quicksilver/ which draweth a very fine line / this whit the women painters vsse" 13 .
These few lines testify to the use of a mercury-based white pigment and are enough to open a little discussion. However, before going into the discussion, it must be assumed that there is no confusion with cerussite/hydrocerussite because Hilliard talks about lead white production a few lines above. The fact that Hilliard delimits the use of this pigment to "women painters" is perplexing. Thornton and Cain (i.e. the editors of his treatise) suggest that Hilliard was referring to the painter Levina Teerlinc, "appointed paintrix to Henry VIII around 1546", but one may also think that he refers to the cosmetic use of the contemporary sublimates.
This last reading is perhaps the least likely. Still, the doubt comes when it is found that Edward Norgate does not mention white quicksilver in the course of dealing with whites and that his 17 th -century manuscript, Miniatura or the Art of Limning, is believed to be largely derived from Hilliard work. On the order hand, Norgate mentions "mercury Sublimata" while discussing a method to produce gold in a fine, fair and cheap way.
The nature of the "sublimate" is clearly described in the third book of "A tracte containing the artes of curious paintinge, carvinge and buildinge, written first in Italian by Paul Lomatius painter of Milan and englished by Richard Haydocke" in 1598: "Of sublimate and the bad effects thereof.
Diverse women use Sublimate diversly prepared for increase of their beauty. Some bray it with quicksilver in a marble morter, with a wodden pestle; and this they call argentatum. Others boile it in water, & therwith wash their face. Some grinde it with Pomatum, and fundry other waies. But this is sure, that which way soever it be used, it is very offensive to mans flesh, and that not only to the face; but unto all the other parts of the body besides, where it is applied. For proofe whereof Sublimate is called deadfier; because of his malignant, and biting nature. The composition whereof is of salte, quicksilver, and vitrioll, distilled together in a glassen vessell.
This the Chirurgions call a corrosive. Because if it bee put upon mans flesh it burneth it in a short space, mortifying the place, not without great paine to the patient. Wherfore such women as use it about their face, haue alwaies black teeth, standing far out of their gums like a Spanish mule; an offensive breath, with a face halfe scorched, and an uncleane complexion. All which proceede from the nature of Sublimate. So that simple women thinking to grow more beautifull, become disfigured, haftening olde age before the time, and giving occasion to their husbandes to seeke strangers i n s t e e d e o f t h e i r w i v e s ; w i t h d i v e r s o t h e r inconveniences." Further information on the cosmetic use of these sublimates is provided by Karim-Cooper (2006), where another recipe handed down by Hugh Plat 14 in 1600 is reported, and in the chapter "Making Calomel" of the Swiderski (2008) book.
In any case, the production of these sublimates and calomel was widespread since earlier times. For example, cosmetic use is documented in China (Needham et al. 1976) and Japan (Takamatsu 1878). Divers (1894) provides a very detailed review of Chinese and Japanese terminology and technology, further supplemented by sketches of the tools and furnaces. One of the recipes mentioned by Divers is reported more succinctly, albeit detailed, by Takamatsu (1878): "According to old history this substance was very early known in the year 714 (the 6 th year of Wado) when it was presented to the empress Gemmiyo from the province of Ise. Up to the present time it has been manufactured only in that province, hence it is also called Ise Oshiroi, which possessing important medicinal properties is mostly used for that purpose rather than as a pigment. (…) The mode of preparation is the following: -A mixture of 2 parts of alum, 1 part of mercury, and 1 part common salt is well pulverized in a mortar until no globules of mercury can be seen. The mass is then placed in a iron pot covered with an earthen ware cover, which is carefully luted up by means of a mixture made from wood ashes and salt water. 36 of such pots are placed in a rectangular furnace, and gradually heated by a charcoal fire for some time, meanwhile the covers are moistened with water. In this way about 2 parts of the calomel can be obtained from 1 part of mercury, subliming on the inner surface of the cover as a white crystalline powder like snow." Recipes vary in relative quantities and procedures on both a geographical and temporal scale, but it is interesting to note the morphological similarity between the Hozukigama, the pot used for sublimation (Fig. 11A), and those used for the production of lead white (see Gliozzo and Ionescu 2021 in this TC).
Based on archaeometric evidence available to date, the deliberate use of calomel as a white pigment has been claimed for a few artworks: four mopa mopa objects -A 17 th century richly decorated barniz de Pasto table cabinet "probably made during the seventeenth century in the northern zone of the Vice-royalty of Peru", two barniz de Pasto gourd flasks and a barniz brilliante casket, all held by the Victoria and Albert Museum in London, UK (Burgio et al. 2018;Melchar et al. 2021). Please note that the authors refer to calomel as "mercury white", whenever it is clear that this material has been used intentionally as a pigment in its own right;  (Cotte et al. 2006).
In conclusion, as far as we know to date, calomel may have been used as a pigment or may have formed as an alteration product. Hence, its occurrence in artworks must be discussed on a case-by-case basis.

Analytical methods for a good practice
Before going into detail, it should be noted that the choice of the methodology to adopt for investigation supports and follows the formulation of archaeological questions and the selection of samples and not vice versa. In many articles, we often read that a technique was chosen because not time-consuming and not expensive but these factors have no value in quality research. The survey methodology must be suitable to answer the research questions and respectful of the artefact's conservation. Other criteria are not to be considered a priority.

Identification and characterisation of the pigment
Identifying cinnabar would be relatively simple if we were a priori sure of the absence of other Hg-based phases. However, we have seen that: (1) other phases such as calomel may be present. Therefore, it is necessary to employ a technique capable of distinguishing the various phases with due accuracy. A simple assumption that determines cinnabar's presence by combining a red pigment's observation with mercury individuation no longer appears sufficient.
(2) the presence of impurities and the morphology of the grains may indicate the nature of cinnabar, i.e. natural or synthetic. This determination requires both microscopic observation and a technique capable of providing the chemical composition of compounds present in small amounts; (3) the surface of the frescoes tends to form thick calcite crusts that can prevent a poorly penetrating beam from reaching the pigment. Therefore, invasive sampling is required unless the find is already detached and lends itself to being transported.
While using a single technique is inadvisable based on the limited result achievable, even the exclusive use of portable techniques may lead to a partially accurate search.
The optimum is therefore achieved with a combination of techniques capable to: observe the pigment (OM, SEM); determine the chemical composition even of elements present in small minimal quantities (SEM, EMPA, LA-ICP-MS or portable XRF when there is really no possibility of transferring the sample/product to the laboratory); provide an unquestionable phase/pigment assessment (XRD, Raman, FTIR).
Undoubtedly, the problems related to the conservation of the artefact are a priority. The help comes from the vast range of portable instruments existing to date and, above all, from large facilities such as synchrotrons. These latter offer different techniques with the advantage of optimised analytical conditions (such as penetration depth). The provenance of the pigment Several authors have repeatedly attempted to determine the provenance of cinnabar through Raman spectroscopy. For example, Villar and Edwards et al. (2005) related the coexistence of cinnabar with calcium carbonates or quartz with a provenance from Tarna or Almaden, respectively. The basic assumption was that the Spanish mines exploited in Roman times were essentially two: Tarna (León) to the north, associated with sedimentary carbonates and Almaden (Ciudad Real) to the south, associated with quartz.
These two methods could provide effective developments in the future, but it seems that both suffer from two main problems: (a) representativeness, due to the investigation of a few areas only and (b) nature of the pigment (natural or artificial). Indeed, one may wonder (a) what these methods' discriminating power could be when the items used for comparison become numerically consistent and (b) are there possible overlaps in spectra and/or structural parameters between natural cinnabar from a given location and artificial cinnabar?
Another issue that does not seem to have been addressed so far (except in part for Almaden) concerns the intra-site variability. This could represent another critical factor in the comparison.
At present, therefore, the most promising techniques seem to be isotopic ones, although much work is still needed before having sufficiently comprehensive and representative data for comparison. In this case, the archaeometric literature may also use geological studies and take advantage of a pre-existing and developing database.
As for sulphur isotopes, data on natural cinnabar occurrences are limited but particularly focused on ancient mining districts (Table 7). This method has been used for provenance investigation by Damiani et al. (2003), Minami et al. (2005), Domínguez-Bella (2010), Spangenberg et al. (2010), Kawano et al. (2014), Tsantini et al. (2018) and Minami et al. (2019). Further data on natural ores are provided by Lavrič and Spangenberg (2003) for the Idrija mine in Slovenia and Jébrak et al. (2002) for the Nuevo Entredicho deposit in Spain. The authors report different methods for sample preparation. Depending on the materials analysed, some considered an initial grinding, followed by analytical techniques such as optical microscopy and XRD, to assess the possible presence of contaminants. Others adopted more laborious procedures including the following steps: 5h heating at 95°C, dilution with a HNO 3 /HCl solution (3:1), washing with ultrapure water, addition of reverse aqua regia to the insoluble part followed by 5h heating at 95°C; cooling, bromine addition, 2h heating at 95°C, washing with ultrapure water, addition of 1-ml BaCl 2 , overnight heating at 65°C, repeated washing with ultrapure water of the resulting barium sulphate, drying and addition of 1 mg of vanadium pentoxide (see Tsantini et al. 2018 for further details). The analyses are typically carried out using isotope ratio mass spectrometers (IRMS), using pure SO 2 gas as a reference. Data are conventionally reported as δ 34 S ‰ (i.e. 34 S/ 32 S) and standardized to the Vienna Cañón Diablo Troilite. The standards mostly used are the IAEA-S-1 and IAEA-S-2 silver sulphides (−0.3% and + 22.7 ± 0.2%, respectively) and, when reported, reproducibility values are better than 3%.
Lead isotopes (Table 8) are consistently used for metal provenancing, first for ancient lead (Brill and Wampler 1967;Grögler et al. 1966) and later also for copper-based alloys (Gale and Stos-Gale 1982;Pernicka et al. 1990Pernicka et al. , 1993Niederschlag et al. 2003). Their use for cinnabar investigation requires suitable sample preparation to eliminate mercury and purify lead. As a matter of fact, 204 Hg interferes with 204 Pb; moreover, the lead isotope ratios of the leachates and residues are different mainly due to lead contamination from associated phases such as pyrite (Higueras et al. 2005). For this reason, sample preparation is as crucial as the analytical technique used for the measurements. Archaeometric issues have been approached through this method by Mazzocchin et al. (2008), Hunt et al. (2011), Minami et al. (2013  and Rodríguez et al. (2020). Other data on cinnabar ores have been further provided by Jébrak et al. (2002), on recrystallised pyrite and Higueras et al. (2005) on cinnabar. These authors used different preparation procedures and analytical techniques; therefore, their results bear different levels of accuracy. Higueras et al. (2005) prepared the sample through the following procedures (in order): grinding, sieving, electromagnetic separation, ultrasonic bath, dissolution via HCl and HNO 3 , heating on a hotplate 100°C for 24 hours and ion exchange in hydrobromic acid. Measurements were performed using a micromass multicollector thermal ionisation mass spectrometer (TIMS). The reference standard was the SRM981 and the results bear an estimated error of 0.15-0.48% for 206 Pb/ 204 Pb, 0.13-1.07% for 207 Pb/ 204 Pb and 0.10-0.45% for 208 Pb/ 204 Pb and an overall confidence level of 95%. Mazzocchin et al. (2008) prepared the sample through the following procedures (in order): dissolution in hydrochloric and nitric acids, heating on a hotplate, cooling and addition of ultra-pure water. The analysis of the samples was performed by quadrupole inductively coupled plasma mass spectrometry (QICP-MS) to study 206 Pb, 207 Pb and 208 Pb. Hunt et al. (2011) did not provide data regarding sample preparation and the accuracy of the proposed results. Their own measurements were achieved using TIMS. Minami et al. (2013Minami et al. ( , 2021 prepared the sample through the following procedures (in order): decomposition with reverse aqua regia, dissolution in hydrochloric acid, ion exchange, dissolution by hydrochloric acid solution and nitric acid and evaporation. Measurements were made by TIMS and MC-ICP-MS.
In this second case, the measurements were corrected using the reference NIST981 and NIST99 standards. The isotopes analysed were 204 Pb, 206 Pb, 207 Pb and 208 Pb. In Minami et al. (2013), the accuracy of the isotopic ratios was of 0.1-0.3% and 0.3-0.6% with 206 Pb and 204 Pb as the denominator, respectively 15 . Rodríguez et al. (2020) prepared the sample through the following procedures (in order): preliminary digestion by HNO 3 (1st day), removal of supernatant and rinsing of the residue with H 2 O, digestion with HF (2nd day), removal of supernatant, rinsing of the residue with H 2 O and XRD, digestion with aqua regia (3rd day), evaporation to dryness, ion exchange in hydrobromic acid, lead elution by HCl. Measurements were made using a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). Correction was obtained by the addition of thallium with NBS997 as isotopic reference material ( 205 Tl/ 203 Tl ratio of 2.3889) and for lead the reference material NBS981 was used. Further tests allowed these authors to measure a 204 Hg contribution lower than 3.5% of the total intensity at mass 204 and established that "accurate Pb ratios are obtained for solutions containing up to 3.6% of Hg and for total signals above 40×10 −14 A on mass 204".
Lastly, Jébrak et al. (2002) analysed recrystallised pyrite instead of cinnabar. After assessing the absence of mercury contamination through the measurement of 202 Table 8 The lead isotopic analyses performed on cinnabar ores (G) and archaeological finds (A).
All measurements were performed on cinnabar samples, except for the first five by Jébrak et al.  Mazzocchin et al. 2008 From these indications, it is possible to assign different values of precision to the proposed results. The reader must consider that, while the typical precision of TIMS is ca. 0.1% or better (Begemann et al. 1995) and the precision of MC-ICP-MS can reach 0.03% and better (Nørgaard et al. 2019), the quadrupole ICP-MS is not able to provide equally precise results. The latter remains at substantially lower precision (0.1%), often ranging between 0.2 and 0.5% (Gulson et al. 2018) and sometimes reaching even the percent range (Miśta-Jakubowska et al. 2019).
Overall archaeometric investigations have shown that (a) it is possible to obtain significant results through isotopic analyses and (b) the investigated cinnabar ores are still few. Conversely, the database used for comparison should be large enough not to incur "false positives" or those cases in which provenance is assessed based on a non-representative ground for comparison.

Concluding summary of key concepts
Was cinnabar that rare and expensive?
The question may come to mind after such a long and geographically large list of occurrences.
Actually, this should be true only for antiquity, that is, when the use of cinnabar is attested in contexts related to kings, queens and wealthy families. Starting from about the 8 th -9 th centuries (before/after depending on the geographical area), the possibility of synthesising vermilion must have gradually lowered its cost.
The rarity of the raw material may undoubtedly have favoured its use in neighbouring regions or regions linked by political and commercial relations with the supply areas, such as Spain and Italy in Roman times. Still, it is too early to trace a diachronic and comprehensive picture of its distribution. On the cinnabar trade, we still have little data available, and, at the same time, 16 Raw data not shown. *Kremer pigmente GmbHαCo, Airchstetten the comparison database for provenance assessment is yet small whatever technique is to be used. The isotopic data are still few and cover only some deposits; therefore, much work is needed to reach a larger geographical area. If more effective techniques are not discovered, it would be advantageous to follow already traced paths, such as measuring sulphur and/or lead isotopes. There is already a database available that only needs to be expanded. What is certain today is that cinnabar has been used to paint almost everything, from human bones to furnishings, from architectural surfaces to manuscripts, from lacquers to lustre. The problems related to fresco painting have been typically solved with the secco technique. The association with other organic and inorganic pigments such as madder lake or minium seems variously motivated. It may reflect a technical skill, aimed at conferring stability to the pigment and preventing the blackening, or it may represent a counterfeit aimed at increasing the weight of the powder to sell it at an even higher price than the declared one. With the use of cinnabar in lustre production, perhaps a sort of technological milestone is reached because cinnabar is no longer used for its beautiful red colour but as a functional additive to reduce copper.
The discoveries relating to the use of calomel as a pigment have opened a new field of investigation, closely related to the study of the degradation products into which cinnabar can transform. However, recent findings have also highlighted that an approximate, albeit quick and inexpensive analytical approach is no longer sufficient or acceptable.
Pending desirable future developments, we may still agree on what to call it. The distinction between natural cinnabar and synthetic vermilion has worked well for a long time, and it would therefore be helpful to keep it.
Acknowledgements I would like to express my very great appreciation to Prof. E. Pernicka, who carefully revised the section focused on isotopic analyses, and to Dr. L. Burgio, who provided me with very valuable tips and advice for drafting the section on calomel. I also sincerely thank the two anonymous reviewers for the constructive feedback. Their comments and suggestions helped improve and clarify this manuscript. Jeff Weissman, Carlos Gonzalez Bargueño, Fabre Minerals and The Arkenstone are kindly acknowledged for allowing me to use the magnificent photos provided in Fig. 1.

Author contribution Not applicable
Funding Open access funding provided by Università degli Studi di Bari Aldo Moro within the CRUI-CARE Agreement.

Data Availability
No new data were created or analysed in this study. The CC-BY licence does not supersede previously copyrighted material. The images provided in Figure 1 remain under owner's copyright.

Declarations
Competing interests The author declares no competing interests.
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