Phoenicochroite

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Phoenicochroite
Phoenicochroite-212833.jpg
Deep red Phoenicochroite cystal, with orange-yellow schwartzembergite. San Francisco Mine, Tocopilla Province, Chile. Photo width 1.5 mm.
General
CategorySulfate (chromate) mineral
Formula
(repeating unit)
Pb2O(CrO4)
Strunz classification7.FB.05
Dana classification35.1.2.1 Anhydrous chromates
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 14 Å, b = 5.67 Å,
c = 7.13 Å; β = 115.22°; Z = 4
Identification
ColorDark red, bright red
Crystal habitTabular crystals; thin coatings, and massive
CleavagePerfect on {201}
TenacitySectile
Mohs scale hardness2 12
LusterAdamantine, resinous
StreakBrick-red
DiaphaneityTranslucent
Specific gravity5.75[1], 7.01[2]
Optical propertiesBiaxial (+)
Refractive indexnα = 2.380, nβ = 2.440, nγ = 2.650
Birefringence0.270 (δ)
2V angle58° (measured)
Other characteristicsHealth risks: contains carcinogenic and mutagenic chromate ion
References[3][1][2][4]

Phoenicochroite, also known as melanochroite, is a lead chromate mineral with formula Pb2OCrO4. It forms striking orange red crystals. It was first discovered in 1839 in Beryozovskoye deposit, Urals, Russia.[1] It is named from the Greek word φοίυικος for "deep red" and χρόα for "color," in allusion to its color.[1]

References[edit]