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]
| Phoenicochroite |
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 Deep red Phoenicochroite cystal, with orange-yellow schwartzembergite. San Francisco Mine, Tocopilla Province, Chile. Photo width 1.5 mm. |
| General |
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| Category | Sulfate (chromate) mineral |
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Formula
(repeating unit) | Pb2O(CrO4) |
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| Strunz classification | 7.FB.05 |
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| Dana classification | 35.1.2.1 Anhydrous chromates |
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| Crystal system | Monoclinic |
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| Crystal class | Prismatic (2/m)
(same H-M symbol) |
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| Space group | C2/m |
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| Unit cell | a = 14 Å, b = 5.67 Å,
c = 7.13 Å; β = 115.22°; Z = 4 |
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| Identification |
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| Color | Dark red, bright red |
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| Crystal habit | Tabular crystals; thin coatings, and massive |
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| Cleavage | Perfect on {201} |
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| Tenacity | Sectile |
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| Mohs scale hardness | 2 1⁄2 |
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| Luster | Adamantine, resinous |
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| Streak | Brick-red |
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| Diaphaneity | Translucent |
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| Specific gravity | 5.75,[1] 7.01[2] |
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| Optical properties | Biaxial (+) |
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| Refractive index | nα = 2.380, nβ = 2.440, nγ = 2.650 |
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| Birefringence | 0.270 (δ) |
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| 2V angle | 58° (measured) |
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| Other characteristics | Health risks: contains carcinogenic and mutagenic chromate ion |
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| References | [3][1][2][4] |
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