Mineral-Geochemical Criteria to Gold and Silver Recovery for Geometallurgical Sampling Campaign on Primorskoe Gold-Silver Deposit

. Ore variability study at Primorskoe gold-silver deposit demonstrated wide variety of mineral composition and gold and silver recoveries with cyanadation. The ore consisted of quartz-feldspar veins, quartz-rhodonite, quartz- “ pyrolusite ” , quartz-epidote-garnet and quartz-Mn-silicates/hydroxides. Todorokite, birnessite, rancieite were the most common among the last ones. Statistical analyses of chemical and mineral composition, parameters of cyanidation tests showed occurrence of three main ore types – feldspatic, manganese silicate and oxide. Gold recovery effected by locking in Fe-oxides. The highest silver recovery strongly correlated with feldspathic cluster and whiter sample color re ﬂ ecting Ag mineral forms: acanthite and electrum. Ore with silicate Mn showed good recoveries of acanthite, electrum and iodargirite associated with Mn silicates. Main silver losses were connected with Mn-oxides content and dark ore coloration where Ag chemically bound in Mn-oxides. Sr and Ba content along with sample color were indications that could be used as a proxy for recovery in geometallurgical mapping and ore-sorting. and native silver and gold. Abundance of speci ﬁ c manganese oxides effected gold and silver extraction by cyanidation. The mineral composition study was aimed to de ﬁ ne causes of possible gold and silver losses with cyanidation tails and possible ways to recover refractory silver.


Introduction
Primorskoe Au-Ag deposit is located in Omsukchan district of Magadan oblast, Russia. It formed by hydrothermal veins of various composition: Qu-Fsp-Chl with Ep, Qu-Rdn-MnO x , Qu-MnO x and Qu-Gar ± Wol. Noble metal mineralization represented with acantite, iodargirite, aurorite, jalpaite, pyrargyrite, electrum, kustelite and native silver and gold. Abundance of specific manganese oxides effected gold and silver extraction by cyanidation. The mineral composition study was aimed to define causes of possible gold and silver losses with cyanidation tails and possible ways to recover refractory silver.
Reagents consumptions (CaO, NaCN) correlated with Mn-cluster, proving that ion exchange might take place during leaching. Zn, Cd, Pb tended to Mn-cluster without connection to a specific Mn-oxide. Sr related to both main clusters equally reflecting isomorphic distribution in feldspathic gangue as well as in MnO x .
Ag recovery demonstrated positive correlation with feldspathic cluster and sample white color (BRT). Ag losses had strong connection with MnO x . Au recovery tied together with color and quartz, Au losses correlated with MnO x and locking. PCA analysis showed same regularities. 6 principal components explained 54.78% of the total variance and described mineral composition (Fig. 2), Mn-and accessory mineralization, noble metal contents and recovery. PCA highlighted strong connection between Ag loses, todorokite and amorphous birnessite.
(1) showed strong relation (R 2 = 0.66) between silver recovery, color (BRT) and some elements contents (in ppm). Variables listed in the order of their significance:

Conclusions
Individual and composite samples of Primorskoe Au-Ag deposit demonstrated variety of mineral composition from high silica and feldspar to Mn-skarn association. Mn mineralization presented in silicates, oxides and hydroxides, carbonate, sulfide had great impact on Ag recovery. Wide range of vein gangue, ore and noble metal mineral associations were similar to ones characteristic for Dukat deposit, the largest silver deposit in Russia. Ag mineral forms affected recovery rate from highest presented by acanthite, electrum in feldspatic association to the lowest locked in Mn-oxides, mainly in todorokite and birnessite. Ore sorting by color and element content can be used.