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Formula: KV3+2(Si3Al)O10(OH)2
Phyllosilicate (sheet silicate),
dioctahedral mica subgroup of the
mica group
Crystal System: Monoclinic
Specific gravity: 2.92 to 2.94 measured, 2.89 calculated
Hardness: 2½
Streak: Greenish white
Colour: Brown, dark green to black
Common impurities: Fe,Ca,Na,H2O
Environments
Sedimentary environments
Hydrothermal environments
Roscoelite is an early stage gangue mineral in low-temperature epithermal
gold-silver-tellurium
deposits, where it
is associated with quartz, pyrite, carbonates,
fluorite and gold. It also occurs in the oxidised
portions of low-temperature sedimentary uranium-vanadium ores, associated with corvusite,
hewettite, carnotite and
tyuyamunite
(HOM).
Localities
The type locality is the Stuckslager Mine, Coloma, Coloma Mining District, West Belt, El Dorado county, California, USA.
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