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Formula: Hg3S2BrCl0.5I0.5
Sulphide of mercury, containing
bromine, chlorine and
iodine
Crystal System: Tetragonal
Specific gravity: 7.23 measured on synthetic material, 7.16 calculated
Hardness: 2½
Streak: Deep yellow to yellow with a slight orange tint
Colour: Bright or dark orange, slowly darkening to brown-orange, then black
Solubility: Fragments blacken in 40% KOH; unaffected by HCl or HNO3
Environments
Although grechishchevite was approved in 1988, to date (February 2025) it has been reported only from the type
localities.
Localities
There are two co-type Localities, the Arzak Hg occurrence, and the Kadyrel' Hg occurrence, Oorash-Khem River Valley,
both in the Uyuk Range, Pi-Khem District, Tuva, Russia.
At the type localities grechishchevite occurs on fracture walls as films consisting of minute prisms and
groups of equant to slightly elongate grains to 0.2 mm (Arzak occurrence), and also as powdery masses and as
concretions of short prismatic crystals to 0.3 mm (Kadyrel occurrence). It occurs sporadically in oxidized
cinnabar ores at the Arzak deposit and less frequently in leached voids at
Kadyrel, in association with numerous other mercury minerals that include
calomel, kuzminite,
cordierite, kadyrelite,
lavrentievite and
eglestonite
(AM 76.1728-1735).
Grechishchevite from the Kadyrel' Hg occurrence
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