Spertiniite

Spertiniite
Spertiniite from Dzhezkazgan, Kazakhstan (size: 5 mm)
General
Category	Oxide mineral
Formula	Cu(OH)2
IMA symbol	Sni1
Strunz classification	4.FD.05
Dana classification	6.2.4.1
Crystal system	Orthorhombic
Crystal class	Pyramidal (mm2) H-M symbol: (mm2)
Space group	Cmc21
Unit cell	a = 2.95 Å, b = 10.59 Å c = 5.27 Å; Z = 4
Identification
Formula mass	97.56 g/mol
Color	Blue, blue-green
Crystal habit	Flat tabular crystals occurring in radial to botryoidal aggregates
Cleavage	None
Tenacity	Brittle
Mohs scale hardness	Soft
Luster	Vitreous
Diaphaneity	Transparent
Specific gravity	3.93
Optical properties	Biaxial
Refractive index	nα = 1.720, nβ= n.d., nγ = > 1.800
Pleochroism	Strong; X = colorless; Z = dark blue
Other characteristics	Decomposes in hot water (synthetic)
References	234

Spertiniite is a rare copper hydroxide mineral. Chemically, it is copper(II) hydroxide with the formula Cu(OH)₂. It occurs as blue to blue-green tabular orthorhombic crystal aggregates in a secondary alkaline environment altering chalcocite. Associated minerals include chalcocite, atacamite, native copper, diopside, grossular, and vesuvianite.³

It was first described in 1981 for an occurrence in the Jeffrey Mine of the Johns-Manville mine, Val-des-Sources, Quebec. It was named for mine geologist Francesco Spertini (born 1937).²³ In addition to the type locality, it has also been reported from Mont Saint-Hilaire, Quebec; Ely, White Pine County, Nevada; and Bisbee, Cochise County, Arizona. It has been reported from Dzhezkazgan, Kazakhstan; from slag at Juliushutte, Astfeld, Harz Mountains, Germany; and from Tsumeb, Namibia.³

A 2006 study has produced evidence the blue mineral chrysocolla may be a microscopic mixture of spertiniite, amorphous silica and water.⁵⁶