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Formula: As4S5
Sulphide of arsenic
Crystal System: Monoclinic
Specific gravity: 3.37 measured, 3.385 calculated
Hardness: 1½
Streak: Yellow
Colour: Yellow
Solubility: Decomposes with 5-mol KOH to dark-brown powder, which dissolves during boiling. No reaction with
hydrochloric or nitric acid, heating in a closed tube produces a white to yellowish sublimate
(Mindat)
Melting Point: Melts at 310 +/- 5 °C
Environments
Localities
At the type locality, the Uzon Caldera, Kronotsky Reserve, Yelizovsky District, Kamchatka Krai, Russia, uzonite
occurs as intergrowths with realgar in the pore spaces of
tuffaceous sediments 10 to 30 cm deep in the caldera. Associated minerals
include realgar, cubic α–arsenic sulphide, amorphous arsenic sulphide,
orpiment, alacranite,
stibnite, cinnabar,
pyrite and sulphur
(HOM ).
Uzonite from the Uzon Caldera - Image
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