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Formula: Cu3As
Arsenide
Crystal System: Isometric
Specific gravity: 7.2 to 7.9 measured, 7.86 calculated
Hardness: 3 to 3½
Streak: black-grey
Colour: Tin white to steel grey
Solubility: Soluble in nitric acid
(Dana)
Common impurities: Sb,S
Environments:
Domeykite is an arsenic mineral of hydrothermal origin, associated
with
copper
(typically arsenian), silver and
algodonite
(HOM, Mindat).
Localities
At the Brunngraben district copper deposit, Flatschach, Knittelfeld, Styria, Austria, domeykite has been
found with
tenorite and also with koutekite
and chalcocite
(Mindat photos).
The type locality is the Los Algodones Mine, El Arrayan, La Serena, Elqui Province, Coquimbo, Chile.
At Běloves, Náchod District, Hradec Králové Region, Czech Republic, domeykite has been found with
cuprite, olivenite,
chrysocolla and malachite
(Mindat photo).
At the Roua Mines, Daluis, Nice, Alpes-Maritimes, Provence-Alpes-Côte d'Azur, France,
lapeyreite was found in the old
copper mines. It is invariably in intimate association with
trippkeite. Other associated minerals include
olivenite, malachite,
gilmarite, cornubite,
connellite,
theoparacelsite,
brochantite, cuprite,
native copper, algodonite and
domeykite
(AM 95.171-176).
At the Cashin Mine, La Sal Mining District, Montrose county, Colorado, USA, domeykite has been found with
algodonite
(Mindat photo).
At the Seneca mine, Mohawk, Keweenaw county, Michigan, USA, domeykite has been found with
nickeline, calcite,
quartz and rammelsbergite
(Mindat photo).
Alteration
At 225oC cubic alpha domeykite decomposes to form
algodonite
(CJC 38.2477-2481).
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