Krennerite

Abstract: Experimental investigations of subsolidus phase relations in the ternary system gold-silver-tellurium are discussed in the light of their significance for interpretation of the mineralogy and conditions of formation of telluride deposits, particularly those of Kalgoorlie, Western Australia, and Vatukoula, Fiji. Calaverite is the most abundant telluride mineral at Kalgoorlie; krennerite, indicated by the experimental results to be the low-temperature, low-pressure polymorph of AuTe 2 , is subordinate, suggesting somewhat higher temperatures and pressures than those obtaining during formation of the Vatukoula deposits, in which krennerite is relatively abundant but calaverite has not been reported.

Abstract: —Gold and silver are capable of forming stable natural compounds with different elements. For gold 36 minerals are known: 10 in the class “Native metals, intermetallic compounds” and 26 in the class “Sulfides (selenides, tellurides, arsenides, antimonides, bismuthides).” For silver, 194 minerals are registered in the MMA, presented in 8 classes. Compared to gold in the class “Native metals, intermetallic compounds” there are far fewer silver minerals. They are widely represented in the classes “Sulfides” and “Sulfosalts” (124). Among silver minerals “halides” are also known (fluorides, chlorides, bromides, iodides), seven; simple and complex oxides, two; there is one mineral each in the classes “sulfates,” “phosphates,” “arsenates,” and “vanadates.” Both metals are in the compositions of 12 minerals: native gold, native silver, weishanite, uytenbogaardtite, petrovskaite, fishesserite, penzhinite, petzite, mutmannite, sylvanite, krennerite, and bezsmertnovite. Every year, the MMA commission registers four to six gold and silver minerals, so there are prospects for the discovery of new minerals of these precious metals in the near future. The indicator elements (fixers) that form natural compounds with gold and indicate the possible presence of gold minerals in sulfide ores include 13 elements: 7 metals (Ag, Cu, Pd, Hg, Sn, Tl, Fe), 3 chalcogens (Te, S, Se), and 3 metalloids (As, Sb, Bi). For silver, this range is wider and also includes such elements as Mn, Zn, Ge, Cd, V, O, H, F, Cl, Br, I, In, and N. This review presents and summarizes the results of studies on the composition of native gold with copper, mercury, and palladium impurities in different types of gold deposits. The article describes the gold and silver minerals established by the author together with colleagues in a study of productive mineral assemblages in some gold deposits in Russia: the Ulakhan, Yunoe, Krutoe, Dzhulietta, Dorozhnoe (Magadan region), Konechnoe (Taimyr Peninsula), Kupol, Valunistoe (Chukotka), Maletoyvayam (Kamchatka), etc. Data are presented on gold and silver minerals found in sulfide ores and of economic importance. Some of their technological properties are characterized, including solubility and behavior under the influence of various reagents. The presence of refractory minerals (calaverite, sylvanite, krennerite, petzite, aurostibite, maldonite, fishesserite, uytenbogaardtite, petrovskaite, penzhinite, weishanite, yuanjianite, hunchunite, anyuite, krynovite, nadjagite, and bogdanovite, bilibinskite, criddleite, etc.), as well as the chemical composition gold and silver, are important technological factors and should be taken into account when developing a technology for extracting precious metals from ores. The presence of increased concentrations of indicator elements (fixers) of gold and silver minerals in sulfide ores is an important indicator and argument for detailed mineralogical and geochemical studies of the source raw material. Identification of mineral (micro-, nano-) forms of gold and silver in sulfide ores is necessary for developing and improving rational dressing schemes.

Abstract: The Panormos Bay Au-Ag-Te vein system, Tinos Island, Greece, which is hosted in Mesozoic marbles, comprises 30 subparallel, steeply dipping quartz veins that extend for at least 500 m. In places, gold telluride mineralization occurs in hydraulic breccias and alteration halos, which are the products of CO 2 effervescence of the ore fluid and wall-rock interaction, respectively. Seventy ore and gangue minerals have been identified. Zones of chlorite, talc, and muscovite-albite-tourmaline alteration, up to 50 cm wide, are associated with precious metal-bearing milky and clear quartz veins. The Au-Ag-Te mineralization is developed in stage V of eight hydrothermal stages. Stage V consists of three substages (early, middle, and late) that are characterized by Ag-, Cu-, and Au-bearing tellurides, respectively. Hessite, sylvanite, altaite, native tellurium, stutzite, cuprian cervelleite, and an unnamed Cu-bearing precious metal sulfotelluride [(Ag,Au,Cu) 9 Te 2 S 3 ] characterize the early substage, whereas melonite, rickardite, vulcanite, weissite, and native tellurium are present in the middle substage. The late substage contains rickardite, kostovite, krennerite, petzite, and calaverite. Unexploited Au-Ag-Te mineralization at Panormos Bay is though to be genetically related to a fluorine- and boron-bearing per-aluminous leucogranite (Tinos leucogranite). A combination of fluid inclusion microthermometry and sylvanite geothermometry suggests that the hydrothermal mineralization was deposited under hydrostatic pressures at a minimum depth of 1 km from moderate-temperature (155°–320°C), low- to moderate-salinity (0.2–13.2 wt % NaCl equiv), effervescing, CO 2 -bearing fluids that contained appreciable amounts of CaCl 2 and MgCl 2 . Calculated isotope compositions of δ 18 O = −3.3 to +5.1 per mil and δD of −73 to −62 per mil for waters in equilibrium with muscovite, quartz, and talc are consistent with the ore fluids being derived from the Tinos leucogranite (δ 18 O = +4.2‰ and δD = −71‰) and their subsequent mixing with a more dilute, low-temperature Miocenic meteoric hydrothermal fluid. Calculated δ 13 C fluid (−2.0 to −0.3‰) and δ 34 S H 2 S (−10.5 to +0.8‰) compositions of the ore fluids indicate an igneous source of carbon and sulfur, which were highly exchanged with a metasedimentary source. Physicochemical conditions of the ore fluids were T = 300° to 200°C, pH = 4.6 to 6.5, f S 2 = 10 −10.9 to 10 −15 , f O 2 = 10 −31.5 to 10 −41 , f Te 2 = 10 −7.7 to 10 −10.7 , f CO 2 = 10 −0.2 to 10 −0.8 , and f H 2 S = 10 −1.7 to 10 −1.8 .