Journal of Thermal Analysis and Calorimetry

, Volume 131, Issue 2, pp 1135–1145 | Cite as

The thermal behaviour of silica varieties used for tool making in the Stone Age

  • Linda C. PrinslooEmail author
  • Elizabet M. van der Merwe
  • Lyn Wadley


Before 100,000 years ago, during the Middle Stone Age (MSA) of South Africa, silica varieties of minerals and rocks were sometimes heated during tool making in order to improve their knapping properties. If the heating and cooling process is not controlled, failure results and the nodules fracture. Recently, we postulated that the reversible α- to β-phase transition may play a role in causing silcrete, a type of rock often used to make stone tools in the Western Cape, to fracture. In this new study, we analyse the thermal behaviour (520–620 °C) of silcrete and compare it to that of two chalcedony samples from different origins, together with samples of chert, agate and flint. These minerals and rocks were commonly used to make stone tools. Differential scanning calorimetry (DSC) measurements show that the α- to β-phase transformation is prominent in silcrete, agate and one of the chalcedony samples, weaker in chert and the second chalcedony sample, but non-existent in flint. X-ray fluorescence (XRF), thermogravimetric analysis (TG) and carbon and sulphur analyses show differences in elemental composition between the rocks and minerals. X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy highlight differences in microstructure. These small differences in chemical composition and structure contribute to a variety of chemical reactions and phase transformations that can take place in rocks and minerals, which in combination determine their stability upon heating and show that care should be taken when generalising thermal behaviour.


Stone tools Thermal behaviour DSC TG XRF XRD FTIR Raman spectroscopy 



The authors would like to thank Dr. Wiebke Grote and Dr. Jeanette Dykstra from the XRD & XRF Facility, Department of Geology, University of Pretoria, for the XRD and XRF measurements, respectively. We thank Paloma de la Peña for providing the flint sample and G. L. Prinsloo for the digital images of the samples. All the authors acknowledge the National Research Foundation (NRF) for financial support. Opinions expressed in the paper are not necessarily those of the NRF. We thank two anonymous reviewers for useful comments that improved this paper.

Supplementary material

10973_2017_6602_MOESM1_ESM.pdf (623 kb)
Supplementary material 1 (PDF 623 kb)


  1. 1.
    Brown K, Marean CW, Herries AIR, Jacobs Z, Tribolo Z, Braun D, Roberts DL, Meyer MC, Bernatchez J. Fire as an engineering tool of early modern humans. Science. 2009;325:859–62.CrossRefGoogle Scholar
  2. 2.
    Crabtree DE, Butler BR. Notes on experiments in flintknapping 1: heat treatment of silica materials. Tebiwa. 1964;7:1–16.Google Scholar
  3. 3.
    Purdy BA, Brooks HK. Thermal alteration of silica minerals: an archaeological approach. Science. 1971;173:322–5.CrossRefGoogle Scholar
  4. 4.
    Domanski M, Webb J. Effect of heat treatment on siliceous rocks used in prehistoric lithic technology. J Archaeol Sci. 1992;19:601–14.CrossRefGoogle Scholar
  5. 5.
    Domanski M, Webb J. A review of heat treatment research. Lithic Technol. 2007;32:153–94.CrossRefGoogle Scholar
  6. 6.
    Borradaile GJ, Kissin SA, Stewart JD, Ross WA, Werner T. Magnetic and optical methods for detecting the heat treatment of chert. J Archaeol Sci. 1993;20:57–66.CrossRefGoogle Scholar
  7. 7.
    Schmidt P, Masseb S, Laurent G, Slodczyk A, Le Bourhis E, Perrenoud C. Crystallographic and structural transformations of sedimentary chalcedony in flint upon heat treatment. J Archaeol Sci. 2012;39:135–44.CrossRefGoogle Scholar
  8. 8.
    Collins MB, Fenwick JM. Heat treating of chert: methods of interpretation and their application. Plains Anthropol. 1974;19:134–45.CrossRefGoogle Scholar
  9. 9.
    Schmidt P, Porraz G, Slodczyk A, Bellot-Gurlet L, Archer W, Miller CE. Heat treatment in the South African Middle Stone Age: temperature induced transformations of silcrete and their technological implications. J Archaeol Sci. 2013;40:3519–31.CrossRefGoogle Scholar
  10. 10.
    Beauchamp EK, Purdy BA. Decrease in fracture toughness of chert by heat treatment. J Mater Sci. 1986;21:1963–6.CrossRefGoogle Scholar
  11. 11.
    Purdy BA. Investigations concerning the thermal alteration of silica minerals: an archaeological approach. Tebiwa. 1974;17:37–66.Google Scholar
  12. 12.
    Olausson DL, Larsson L. Testing for the presence of thermal pretreatment of flint in the Mesolithic and Neolithic of Sweden. J Archaeol Sci. 1982;9:275–85.CrossRefGoogle Scholar
  13. 13.
    Wadley L, Prinsloo LC. Experimental heat treatment of silcrete implies analogical reasoning in the Middle Stone Age. J Human Evol. 2014;70:49–60.CrossRefGoogle Scholar
  14. 14.
    Cairncross B. Field guide to rocks and minerals of Southern Africa. Cape Town: Struik; 2004.Google Scholar
  15. 15.
    Webb J, Finlayson B, Cochrane G, Doelman T, Domanski M. Silcrete quarries and artefact distribution in the Central Queensland Highlands, Eastern Australia. Archaeol Ocean. 2013;48:130–40.Google Scholar
  16. 16.
    Smykatz-Kloss W, Klinke W. The high-low quartz inversion—key to the petrogenesis of quartz-bearing rocks. J Therm Anal. 1997;48:19–38.CrossRefGoogle Scholar
  17. 17.
    Loubser M, Verryn S. Combining XRF and XRD analyses and sample preparation to solve mineralogical problems. S Afr J Geol. 2008;111:229–38.CrossRefGoogle Scholar
  18. 18.
    Raman CV, Nedungadi TMK. The alpha beta transformation of quartz. Nature. 1940;145:147.CrossRefGoogle Scholar
  19. 19.
    Rao CNR, Gopalakrishnan J. New directions in solid state chemistry. In: Cambridge solid state science series. Cambridge: Cambridge University Press; 1986. p. 148-155.Google Scholar
  20. 20.
    Barker C, Robinson SJ. Thermal release of water from natural quartz. Am Miner. 1984;69:1078–81.Google Scholar
  21. 21.
    Colomban Ph, Slodczyk A. The structural and dynamics neutron study of proton conductors: difficulties and improvement procedures in protonated perovskite. A Eur Phys J Spec Top. 2012. doi: 10.1140/epjst/e2012-01670-7.Google Scholar
  22. 22.
    Kerr R, Wood N. Science and civilisation in China Volume 5: chemistry and chemical technology, Part 12, ceramic technology. Cambridge: Cambridge University Press; 2004. p. 57. ISBN, 0521838339, 9780521838337.Google Scholar
  23. 23.
    Ríos S, Salje EKH, Redfern SAT. Nanoquartz versus macroquartz: a study of the αβ phase transition. Eur Phys J B. 2001;20:75–83.CrossRefGoogle Scholar
  24. 24.
    Dubrawski JV. The effect of particle size on the determination of quartz by differential scanning calorimetry. Thermochim Acta. 1987;120:257–60.CrossRefGoogle Scholar
  25. 25.
    Blasy M. Variability of α/ß inversion temperatures of natural quartz. Int J Sci Res. 2014;3(10):454–8.Google Scholar
  26. 26.
    Vettegren VI, Sobolev GA, Kireenkova SM, et al. Effect of water on the αβ phase transitionin a surface quartz layer. Phys Solid State. 2014;56:1228–33. doi: 10.1134/S1063783414060377.CrossRefGoogle Scholar
  27. 27.
    Ghiorso MS, Carmichael ISE, Moret LK. Inverted high-temperature quartz. Contrib Miner Pet. 1997;68:307–23.CrossRefGoogle Scholar
  28. 28.
    Kostyrko K, Skoczylas M, Klee A. Certified reference materials for thermal analysis. J Therm Anal. 1988;33:351–7.CrossRefGoogle Scholar
  29. 29.
    Colomban Ph. Proton and protonic species: the hidden face of solid state chemistry. How to measure H-content in materials? Fuel Cells. 2013;13(1):6–18.CrossRefGoogle Scholar
  30. 30.
    Xing Z, Beaucour A, Hebert R, Noumowe A, Ledesert B. Influence of the nature of aggregates on the behaviour of concrete subjected to elevated temperature. Cem Concrete Res. 2011;41(4):392–402.CrossRefGoogle Scholar
  31. 31.
    Razafinjato RN, Beaucour A, Hebert RL, Ledesert B, Bodet R, Noumowe A. High temperature behaviour of a wide petrographic range of siliceous and calcareous aggregates for concretes. Constr Build Mater. 2016;123:261–73.CrossRefGoogle Scholar
  32. 32.
    Tucker ME. Sedimentary petrology: an introduction to the origin of sedimentary rocks. 3rd ed. Oxford: Blackwell Science; 2001.Google Scholar
  33. 33.
    Adamo I, Ghisoli C, Caucia F. A contribution to the study of FTIR spectra of opals. N Jb Miner Abh. 2010;187(1):63–8.CrossRefGoogle Scholar
  34. 34.
    Gouadec G, Colomban Ph. Raman spectroscopy of nanostructures and nanosized materials. J Raman Spectrosc. 2009;38:598–603.CrossRefGoogle Scholar
  35. 35.
    Froment F, Tournié A, Colomban Ph. Raman identification of natural red to yellow pigments: ochre and iron-containing ores. J Raman Spectrosc. 2008;39:560–8.CrossRefGoogle Scholar
  36. 36.
    Fritsch E, Rossman GR. An update on color in gems. Part 1: introduction and colors caused by dispersed metal ions. Gems and Gemology. 1987;23(3):126–39.CrossRefGoogle Scholar
  37. 37.
    López A, Frost RL. Raman spectroscopy of pyrite in marble from Chillagoe, Queensland. J Raman Spectrosc. 2015;46(10):1033–6.CrossRefGoogle Scholar
  38. 38.
    Wadley L, de la Peña P, Prinsloo LC. Thermal responses of South African agate and chalcedony when heated experimentally, and the global implications for heated archaeological minerals. J. Field Archaeol. 2017 online.Google Scholar
  39. 39.
    Labus M. Thermal methods implementation in analysis of fine-grained rocks containing organic matter. J Therm Anal Calorim. 2017;15:1–9.Google Scholar
  40. 40.
    Sitarz M, Wyszomirski P, Handke B, Jelen P. Moganite in selected Polish chert samples: the evidence from MIR, Raman and X-ray studies. Spectrochim Acta Mol Biomol Spectrosc. 2014;122:55–8.CrossRefGoogle Scholar
  41. 41.
    Schmidt P. What causes failure (overheating) during lithic heat treatment? Archaeol Anthropol Sci. 2014;6(2):107–12.CrossRefGoogle Scholar
  42. 42.
    Schmidt P, Badou A, Fröhlich F. Detailed FT near-infrared study of the behavior of water and hydroxyl in sedimentary length-fast chalcedony, SiO2, upon heat treatment. Spectrochim Acta Part A. 2011;81:552–9.CrossRefGoogle Scholar
  43. 43.
    Zhang LH, Gong H, Wang JP. Thermal decomposition kinetics of amorphous carbon nitride and carbon films. J Phys Condens Matter. 2002;14:1697–708.CrossRefGoogle Scholar
  44. 44.
    Damby DE, Llewellin EW, Horwell CJ, Williamson BJ, Najorka J, Cresseye G, Carpenter M. The αβ phase transition in volcanic cristobalite. J Appl Cryst. 2014;47:1205–15.CrossRefGoogle Scholar
  45. 45.
    Mercieca A. Burnt and broken: an experimental study of heat fracturing in silcrete. Aust Archaeol. 2000;51:40–7.CrossRefGoogle Scholar

Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2017

Authors and Affiliations

  1. 1.Centre for Archaeological Science, School of Earth and Environmental SciencesUniversity of WollongongWollongongAustralia
  2. 2.Department of PhysicsUniversity of PretoriaHatfieldSouth Africa
  3. 3.Department of ChemistryUniversity of PretoriaHatfieldSouth Africa
  4. 4.Evolutionary Studies Institute, and the Centre of Excellence, PalaeosciencesUniversity of the WitwatersrandJohannesburgSouth Africa

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