Fraipontite

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Fraipontite
Fraipontite-sea52a.jpg
Pockets of minute pearly white fraipontite crystals with green smithsonite from Laurium, Greece (size: 1.4 x 1.0 x 0.9 cm)
General
Category Phyllosilicate
Formula
(repeating unit)
(Zn,Al)3(Si,Al)2O5(OH)4
Strunz classification 09.ED.15
Crystal symmetry Monoclinic domatic
H-M symbol: (m)
Space group: Cm
Unit cell a = 5.34 Å, b = 9.21 Å, c = 14.12 Å; β = 93.2°; Z = 2
Identification
Color Blueish, yellow white light green
Crystal habit Fibrous to porcelaneous massive
Crystal system Monoclinic
Mohs scale hardness 3.5 – 4
Luster Silky
Streak White to pale green
Diaphaneity Opaque to translucent
Specific gravity 3.08 – 3.10
Optical properties Biaxial (-)
Refractive index nα = 1.620 nβ = 1.624 nγ = 1.624
Birefringence δ = 0.004
2V angle Measured: 15° to 20°
References [1][2][3]

Fraipontite is a zinc aluminium silicate mineral with a formula of (Zn,Al)3(Si,Al)2O5(OH)4.[1][2]

It is a member of the kaolinite-serpentine mineral group and occurs as an oxidation product of zinc deposits. It occurs with smithsonite, gebhardite, willemite, cerussite and sauconite.[1]

It was first described in 1927 for an occurrence in Vieille Montagne, Verviers, Liège Province, Belgium.[2] It was named for Julien Jean Joseph de Fraipont (1857–1910), and Charles de Fraipont, geologists of Liege, Belgium.[3] In addition to the type locality in Belgium, it has been reported from Tsumeb, Namibia; Laurium, Greece; Swaledale, North Yorkshire, England; the Silver Bill mine, Cochise County, Arizona, the Blanchard Mine, Socorro County, New Mexico and the Mohawk mine, San Bernardino County, California in the USA; and from the Ojuela mine, Mapimi, Durango, Mexico.[1]

A synonym for fraipontite is zinalsite which was reported in 1956 for an occurrence in Kazakhstan.[4][5]

References[edit]

External links[edit]

Media related to Fraipontite at Wikimedia Commons