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Formula: Pb6Cr3+(Cr6+O4)2(SO4)(OH)7FCl
Sulphate, chromium-bearing mineral (both Cr3+ and Cr6+)
Crystal System: Trigonal
Specific gravity: 5.878 calculated
Hardness: 2½ to 3
Streak: White
Colour: Orange-brown to red-brown
Solubility: Insoluble in water or hydrochloric acid
Environments
Evanichite is a new mineral, approved in 2022 and to date (August 2023) reported only from the type locality.
Localities
At the type locality, the Mammoth-Saint Anthony mine, St. Anthony deposit, Tiger, Mammoth Mining District, Pinal County,
Arizona, USA, mineralisation is a series of veins within shear zones. Their gangue consists of
brecciated country rock cemented and replaced with
quartz and calcite together with
some baryte and fluorite.
Evanichite occurs as a single group of subparallel short orange-brown to red-brown, transparent prismatic
crystals on top of the quartz matrix. Individual crystals are up to 0.70 x
0.20 x 0.20 mm3 in size. The host matrix for evanichite is
quartz, and associated minerals include
georgerobinsonite,
bobmeyerite, pinalite,
diaboleite, boleite,
leadhillite, caledonite,
cerussite, calcite,
baryte and fluorite
(CJMP 61.419-429).
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