Elizabeth hill26 Sep 2020 12:24
A massive Coup for UFO
The deposit is hosted by granite, monzogranite, intrusive gabbro and pyroxenite. The last two form rafts, 2m-+50m within the granite, dipping west. The Munni Munni Fault and basal contact of the Minni Munni Complex are the structural controls on the veining. The veins dip near vertical, 10-15 metres wide. One source states there were four pods or ore shoots, plunging shallowly south, 20-80 metres long, 5 to 15 metres wide, showing stratiform concentrations of Ni-Cu sulphides, and variable PGE.
At the 82 metre level, the drive exposed the core of the vein system, as a 15 metre wide body of carbonate-quartz breccia containing pyroxenite and granite. The veins contained 1% Ag, with 20% of this native silver as veins, sheets, wires, crystals, globules, and dendrites. Remaining minerals showed a complex of Ag sulphides and sulphosalts, and base metal sulphides, amounting to 60 ore species (which annoyingly the source does not list), including native metals, alloys and sulphides. Gangue minerals are quartz, calcite, calcian siderite, and chlorite.
Within the system is a layered mafic-ultramafic intrusion of pyrrhotite, chalcopyrite, pentlandite, and PGE's; hydrothermal Cu-Zn-Pb like chalcopyrite, sphalerite and galena, and an exotic suite of Ag sulphides containing Ni, Co, Cu, Zn, Pb, As, Sb values, with argentopentlandite given as an example.
The dominant mineral assemblage is primary, but supergene minerals like marcasite, violarite, millerite and mckinstryite do exist, with oxidised products like goethite down to a depth of 100 metres. Acanthite is noted as being widespread.
Western Australia is one of the most mineral rich regions in the world, yet mineral specimens are comparatively rare. Large mining companies view mineral specimen collecting as little more than a nuisance. The Elizabeth Hill Mine was small enough to see value in providing specimens, and in 1999 an Australian dealer was able to access the site.
The dealer described lumps of pure silver masses up to 40kg in the ore dump, and the mine reported masses to 100kg. He noted also silver wires in the underground workings. The dealer was able to collect undamaged specimens to 11 kg. He also noted vanadanite, chalcanthite, galena, and unidentified silver halides on the ore stockpile. A few hundred silver specimens were collected and many of these are now in circulation. There were also a few specimens of red prismatic vanadinite crystals up to 3.5 mms long on calcite, as well as specimens of chlorargyrite micro-crystals placed on the Australian market at this time. Little else is believed to be in the collector market, although the deposit would have readily provided other species, had the opportunity existed.
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