Valleriite

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.

Valleriite
Cubanite (brass yellow), maucherite (dark gray) and valleriite (dark bronze), mainly
General
Category	Sulfide mineral
Formula	(Fe2+,Cu)4(Mg,Al)3S4(OH,O)6
Strunz classification	2.FD.30
Dana classification	2.14.1.1
Crystal system	Trigonal[1]
Crystal class	Hexagonal scalenohedral (3m) H-M symbol: (3 2/m)
Space group	R3m
Unit cell	a = 3.79, c = 34.1 [Å]; Z = 2
Identification
Color	Bronze-yellow, gray
Crystal habit	Massive, nodular, encrustations, thin splintery
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]

Discovery and occurrence

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]