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Formula: Cu8S5
With oxidation states: Cu1+6Cu2+2(S2-)5 (CM 23.61-76)
Sulphide, chalcocite group
Crystal System: Trigonal
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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