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Deep red Phoenicochroite cystal, with orange-yellow schwartzembergite. San Francisco Mine, Tocopilla Province, Chile. Photo width 1.5 mm.
Category Sulfate (chromate) mineral
(repeating unit)
Strunz classification 7.FB.05
Dana classification Anhydrous chromates
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/m
Unit cell a = 14 Å, b = 5.67 Å,
c = 7.13 Å; β = 115.22°; Z = 4
Color Dark red, bright red
Crystal habit Tabular crystals; thin coatings, and massive
Cleavage Perfect on {201}
Tenacity Sectile
Mohs scale hardness 2 12
Luster Adamantine, resinous
Streak Brick-red
Diaphaneity Translucent
Specific gravity 5.75[1], 7.01[2]
Optical properties Biaxial (+)
Refractive index nα = 2.380, nβ = 2.440, nγ = 2.650
Birefringence 0.270 (δ)
2V angle 58° (measured)
Other characteristics Health 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]