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Formula: Cu2AgAsS4
Sulphosalt, copper-, silver- and
arsenic- bearing mineral,
stannite group
Crystal System: Tetragonal
Specific gravity: 4.663 calculated for the empirical formula
Hardness: 4 to 5
Streak: Black
Colour: Grey colour with a slight green-brassy tint
Luminescence: No fluorescence under UV
Environments
Localities
At the type locality, the Uchucchacua Mine, Uchucchacua area, Oyón District, Oyón Province, Lima, Peru, the sample
studied consists predominantly of alabandite and Mn-bearing
calcite with associated crystals of
manganoquadratite,
proustite and
billingsleyite, as well as massive
diaphorite and
seligmannite-bournonite.
Keutschite occurs as rare metallic, highly lustrous, blocky, free-standing crystals up to 3 mm in size that
have a grey colour with a slight green-brassy tint on
manganoquadratite and
proustite crystals. Keutschite has a metallic lustre and a black
streak and is non-fluorescent
(EJM 38.1.1-7).
Keutschite from Uchucchacua Mine -
Image
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