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Pharmacosiderite

Pharmacosiderite
Pharmacosiderite-231258.jpg
General
Category Arsenate minerals
Formula
(repeating unit)
KFe4(AsO4)3(OH)4·(6-7)H2O
Strunz classification 8.DK.10
Crystal system Isometric
Crystal class Hextetrahedral (43m)
H-M symbol: (4 3m)
Space group P43m
Identification
Formula mass 873.38 g/mol
Color Greens, browns, yellows
Crystal habit Massive to Crystalline
Cleavage Distinct on the [100]
Fracture Brittle
Mohs scale hardness 2 1/2
Luster Adamantine
Streak yellowish green
Diaphaneity Subtransparent to subtranslucent
Density 2.9 g/cm³
Ultraviolet fluorescence None
References

Pharmacosiderite is a hydrated basic ferric arsenate, with chemical formula KFe4(AsO4)3(OH)4·(6-7)H2O and a molecular weight of 873.38 g/mol. It consists of the elements arsenic, iron, hydrogen, potassium, sodium and oxygen. It has a Mohs hardness of 2 to 3, about that of a finger nail. Its specific gravity is about 2.7 to 2.9, has indistinct cleavage, and is usually transparent or translucent. It has a yellow or white streak and a yellow, green, brown or red color. Its lustre is adamantine, vitreous and resinous, and it has conchoidal, brittle and sectile fracture.


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Wikipedia

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