Geerite

geerite

spionkopite

chromite

pentlandite

Images

Formula: Cu8S5
With oxidation states: Cu1+6Cu2+2(S2-)5 (CM 23.61-76)
Sulphide, chalcocite group
Specific gravity: 5.61 calculated
Hardness: 3½ to 4
Colour: Bluish-white, may be iridescent
Common impurities: Fe,Zn
Environments

Sedimentary environments
Metamorphic environments

Geerite occurs in serpentine hosted chromite-magnetite deposits, associated with andradite, chalcopyrite, chlorite, chromite, diopside, magnetite, pentlandite and spionkopite. Geerite may be partly or completely replaced by spionkopite (Mindat).

Localities

At Eretria, Euboea, Central Greece, Greece, geerite occurs in a serpentine hosted chromite-magnetite deposit associated with spionkopite, chalcopyrite, cobaltpentlandite, magnetite, chromite, andradite, chlorite and diopside (HOM).

At the type locality, the geerite locality, De Kalb Township, St. Lawrence county, New York, USA, geerite occurs as a thin, iridescent coating or as platelets up to approximately 15 microns thick. In some specimens geerite is partly or completely replaced by spionkopite. Other associated minerals include sphalerite, tetrahedrite, chalcopyrite, malachite, azurite, brochantite, chrysocolla, cervantite, stibiconite, hemimorphite and calcite (CM 18.519-523).

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