Formula: Ag5Cu3S4
Sulphide of silver and copper
Crystal System: Orthorhombic
Specific gravity: 6.61 measured, 6.57 calculated
Hardness: 1½ to 2½
Streak: Dark steel-grey
Colour: Steel-grey, tarnishes to dark grey to black

Hydrothermal environments

Mckinstryite is of hydrothermal or supergene origin, probably formed below 94.4oC, the upper stability limit for mckinstryite (HOM).


At the Sedmochislenitsi mine, Balkan Mts, Vratsa Province, Bulgaria, mckinstryite is associated with bornite, chalcocite, chalcopyrite, djurleite, digenite, tennantite, stromeyerite, wittichenite, bismuth, rammelsbergite, balkanite, mercurian silver, cinnabar, pyrite, calcite, baryte and aragonite (HOM).

At the Echo Bay mine, Port Radium District, Great Bear Lake, North Slave Region, Northwest Territories, Canada, mckinstryite occurs as a late-stage, primary sulphide in the uranium = cobalt - nickel - silver - bismuth deposit, accompanying nickeline, rammelsbergite, chalcopyrite, bornite, covellite and early dolomite (EG 66.342-347).

At the type locality, the Foster mine, Coleman Township, Cobalt area, Cobalt-Gowganda region, Timiskaming District, Ontario, Canada, mckinstryite occurs as masses of intergrown crystals 0.2 to 3 mm in diameter in a silver - cobalt - nickel - copper deposit. Associated minerals include chalcopyrite, stromeyerite, calcite, actinolite, silver and arsenopyrite (Mindat).

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