Silver sulphosalts from the Meerschaum Mine, Mt. Wills, Victoria, Australia

Abstract

A rich vein of silver and silver-lead sulphosalt minerals was discovered in 1906 in the Meerschaum Mine, on the Sunnyside goldfield at Mt. Wills, in northeastern Victoria. Andorite, miargyrite, tetrahedrite (freibergite), owyheeite, and argentian gold are the main silver-bearing minerals present, and sphalerite, pyrite, arsenopyrite, and covelline also occur in the vein.The vein was probably emplaced under epithermal conditions from ore fluids accompanying the intrusion of the Mt. Wills granite. The main silver-bearing minerals were probably deposited at temperatures ranging from about 350 ° to below 300 °C.

Ag-Cu Exchange Equilibria Between α-Miargyrite, Chalcostibite, Pyrargyrite, and High-Skinnerite: Constraints on Ag-Cu Mixing in α-Miargyrite and Chalcostibite

“…A positive value of 14.0 kJ/gfw for DG Å * X Cu s (Eqn 15) is indicative that miargyrite is willing to take in only very limited amounts of Cu on either the A or B site which is also consistent with the relatively large values of both W AgCu A Mrg and W AgCu B Mrg and with the observation that in nature, Cu substitution for Ag in miargyrite is very low, generally <1% (cf. Birch, 1981Birch, , 1992Sugaki et al, 1982Sugaki et al, , 1984Sugaki et al, , 1986Kaspar et al, 1983Kaspar et al, , 1985Nakayama, 1986;Kaspar et al, 1991).…”

Mineralogy of the Silver King deposit, Omeo, Victoria

“…However, there are no quantitative analyses of either the gold or the tetrahedrite to enable modelling of the distribution of silver in the ore. Silver yields from the Sunnyside mines to the north were not reported, but silver sulphosalt minerals have been recorded from a number of the reefs (Birch 1992). Chief among these was a late-stage vein in the Meerschaum mine containing an early pyritearsenopyrite-sphalerite assemblage followed by andorite, freibergite, miargyrite and owyheeite (Birch 1981).…”

“…It is possible that Stillwell observed andorite but misidentified it as tetrahedrite. The Silver King deposit is the second occurrence of andorite in the Omeo region, with the mineral being the main silverbearing phase in a late-stage quartz vein found in the Meerschaum mine on the Mt Wills goldfield (Birch 1981).…”

“…Stillwell (1933Stillwell ( , 1946 identified pyrargyrite as the main mineral responsible for high silver contents in the ore, occurring with other sulphide minerals, including 'tetrahedrite' and a mineral with optical and chemical properties that resembled lengenbachite (Stillwell 1946). The likelihood of additional silver-bearing phases being present has triggered the current investigation, which may also place the mineralisation in a regional context that includes the silver-bearing assemblages in the Glen Wills and Sunnyside goldfields north of Omeo (Birch 1981(Birch , 1992.…”

An unusual form of coated diamond

“…It appears that in these deposits the Sn present in the ore-forming environment formed tin minerals at relatively high temperatures, while andorite is a product of late-stage processes at lower temperatures. Recent analyses of andorite from various occurrences (Borodaev et al, 1971;Birch, 1981;Makovicky andMumme, 1983 andMoelo, 1983) all show an absence of Sn.…”