Spertiniite

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

Spertiniite
Spertiniite from Dzhezkazgan, Kazakhstan (size: 5 mm)
General
CategoryOxide mineral
Formula
(repeating unit)		Cu(OH)2
Strunz classification4.FD.05
Dana classification6.2.4.1
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
H-M symbol: (mm2)
Space groupCmc21
Unit cella = 2.95 Å, b = 10.59 Å
c = 5.27 Å; Z = 4
Identification
Formula mass97.56 g/mol
ColorBlue, blue-green
Crystal habitFlat tabular crystals occurring in radial to botryoidal aggregates
CleavageNone
TenacityBrittle
Mohs scale hardnessSoft
LusterVitreous
DiaphaneityTransparent
Specific gravity3.93
Optical propertiesBiaxial
Refractive indexnα = 1.720, nβ= n.d., nγ = > 1.800
PleochroismStrong; X = colorless; Z = dark blue
Other characteristicsDecomposes in hot water (synthetic)
References[1][2][3]

Discovery and occurrence

It was first described in 1981 for an occurrence in the Jeffrey quarry of the Johns-Manville mine, Asbestos, Estrie, Québec. It was named for mine geologist Francesco Spertini (born 1937).[1][2] 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.[2]

A 2006 study has produced evidence the blue mineral chrysocolla may be a microscopic mixture of spertiniite, amorphous silica and water.[4][5]

Crystal structure of spertiniite
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References
  1. Spertiniite on Mindat
  2. Spertiniite in the Handbook of Mineralogy
  3. Spertiniite on Webmineral
  4. François Farges, Karim Benzerara, Gordon E. Brown, Jr.; Chrysocolla Redefined as Spertiniite; SLAC-PUB-12232; 13th International Conference On X-Ray Absorption Fine Structure (XAFS13); July 9-14, 2006; Stanford, California
  5. Chrysocolla on Mindat
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