Mawsonite

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Formula: Cu₆Fe₂SnS₈
Sulphide, tin-bearing mineral
Crystal System: Tetragonal
Specific gravity: 4.65 calculated
Hardness: 3½ to 4
Colour: Brownish orange
Magnetism: Ferromagnetic
Common impurities: Zn,Se
Environments

Igneous environments
Metamorphic environments
Hydrothermal environments

occurs in massive to disseminated hydrothermal copper ores within highly altered volcanic rocks, in skarn, and disseminated in altered granite; it is rare in copper porphyry deposits. It is usually associated with bornite, and other associated minerals include pyrite, chalcopyrite, chalcocite, digenite, idaite, stannite, stannoidite, pyrrhotite, pentlandite, tetrahedrite–tennantite, enargite, luzonite–famatinite, kiddcreekite, mohite, bismuth, galena and sphalerite (HOM).

Localities

There are two co-type localities, the Royal George mine, Tingha, Hardinge county, New South Wales, Australia, and the North Lyell mine, Mount Lyell Mines, Queenstown district, West Coast municipality, Tasmania, Australia.

At the Royal George mine, Tingha, Hardinge county, New South Wales, Australia, the mineralisation occurs in a narrow quartz vein along shears in granite. The paragenesis includes cassiterite, bornite, stannoidite, mawsonite, chalcocite, enargite and arsenopyrite. Replacement of cassiterite by bornite has formed characteristic microscopic reaction rims, consisting largely of stannoidite with mawsonite occurring around the outer margins. Mawsonite also occurs rarely within chalcocite rims surrounding bornite. The grain size of mawsonite from Tingha is rarely in excess of .03 mm (AM 50.900-908).

At the North Lyell mine, Mount Lyell Mines, Queenstown district, West Coast municipality, Tasmania, Australia, mawsonite occurs as inclusions in bornite. The copper deposits of the Mount Lyell district occur as massive to disseminated orebodies within highly altered volcanic rocks. The main ore minerals present include pyrite, chalcopyrite, bornite, chalcocite, digenite, tetrahedrite–tennantite, enargite, sphalerite and galena. The presence of the orange mineral later identified as mawsonite was first reported in 1939. The mawsonite occurs typically as rounded to irregular inclusions in bornite, to a maximum observed grain size of 1.3 mm. The most common assemblages are bornite-chalcocite, bornite-chalcopyrite-tetrahedrite and bornite-chalcopyrite-pyrite. Other associated minerals include galena, tennantite and an enargite-type phase (AM 50.900-908).

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