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Formula: Ag3AsS3
Sulpharsenite,
proustite group, monoclinic
paramorph
of proustite, which is trigonal; the xanthoconite →
proustite transition occurs at 180-202oC (Mindat).
Crystal System: Monoclinic
Specific gravity: 5.54 measured, 5.53 calculated
Hardness: 2 to 3
Streak: Orange-yellow
Colour: Red-orange, yellow-orange, red-brown, brown
Environments
Xanthoconite typically is associated with other silver sulphosalts in hydrothermal veins.
Associated minerals include
proustite, pyrargyrite,
acanthite, arsenic and
calcite
(HOM, Mindat).
Localities
The type locality is the Himmelsfürst mine, Brand-Erbisdorf, Mittelsachsen, Saxony, Germany.
At the Imiter mine, Tinghir Cercle, Tinghir Province, Drâa-Tafilalet Region, Morocco, xanthoconite is chiefly confined to the
quartz veins of the later-stage silver assemblages, where
silver it is associated with
polybasite-pearceite,
galena, and less commonly with arsenopyrite.
It is also found in small amounts in cavities in black shale with
proustite and titanite
(Min Rec 42.2.133-135).
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