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Formula: Zn2(Se4+O3)Cl2
Anhydrous selenite
Crystal System: Orthorhombic
Specific gravity: 3.64 calculated
Hardness: 2 to 2½
Streak: White
Colour: Colourless, becoming sky blue on long exposure to air
Solubility: Readily soluble in dilute acids, soluble with difficulty in water
Environments
Sofiite is a fumarole mineral. On exposure to air it becomes turbid white, and crystals bend and swell;
decomposition products form radial aggregates
(Mindat).
Localities
At the type locality, the Tolbachik volcano, Kamchatka Krai, Russia, sofiite occurs in fractures in volcanic
fumaroles as well-formed, pseudohexagonal thin-platy to micalike crystals associated with cotton-like hygroscopic
masses of phases containing zinc and chlorine. Associated minerals include
tenorite, cotunnite,
piypite, ponomarevite,
chalcocyanite, chloromenite,
burnsite, ilinskite,
georgbokiite, dolerophanite,
halite, sylvite and
gold. The specimens were collected at temperatures 180 to 230oC
(AM 75.1211-1212, HOM).
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