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Cubanite (brass yellow), maucherite (dark grey) and valleriite (dark bronze), mainly.
Category Sulfide mineral
(repeating unit)
Strunz classification 2.FD.30
Dana classification
Crystal symmetry Trigonal - hexagonal scalenohedral
H-M symbol: (32/m)
Space group: R3m
Unit cell a = 3.79 Å, c = 34.1 Å; Z=2
Color Bronze-yellow, gray
Crystal habit Massive, nodular, encrustations, thin splintery
Crystal system Trigonal[1] Hexagonal[2]
Cleavage Excellent on {0001}
Mohs scale hardness 1 - 1.5
Luster Metallic
Streak Black
Diaphaneity Opaque
Specific gravity 3.14 (measured)
Pleochroism Strong; pale yellow to deep brown
References [2][3][1]

Valleriite is an uncommon sulfide mineral (hydroxysulfide) of iron and copper with formula: 4(Fe,Cu)S·3(Mg,Al)(OH)2[3] or (Fe2+,Cu)4(Mg,Al)3S4(OH,O)6.[2] It is an opaque, soft, bronze-yellow to brown mineral which occurs as nodules or encrustations.

Discovery and occurrence[edit]

Valleriite was first described in 1870 from an occurrence in Västmanland, Sweden. It was named for Swedish chemist Johan Gottschalk Wallerius (Vallerius) (1709–1785).

Valleriite occurs in dunites and chromitites replacing chalcopyrite in Cyprus. In Phalaborwa, South Africa it occurs as replacement of magnetite in a carbonatite. It occurs as replacements of copper and nickel phases in serpentinites and other altered ultramafic rocks.[3]