Fraipontite

 Fraipontite is a zinc aluminium silicate mineral with a formula of (Zn,Al)

3(Si,Al)
2O
5(OH)
4.

Fraipontite
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) 2O 5(OH) 4
Strunz classification	9.ED.15
Crystal system	Monoclinic
Crystal class	Domatic (m) (same H-M symbol)
Space group	Cm
Unit cell	a = 5.34, b = 9.21 c = 14.12 [Å]; β = 93.2°; Z = 2
Identification
Color	Blueish, yellow white light green
Crystal habit	Fibrous to porcelaneous massive
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]

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.

It was first described in 1927 for an occurrence in Vieille Montagne, Verviers, Liège Province, Belgium. It was named for Julien Jean Joseph de Fraipont (1857–1910), and Charles de Fraipont, geologists of Liege, Belgium. 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 US; and from the Ojuela mine, Mapimi, Durango, Mexico.

A synonym of the fraipontite is the zinalsite, which was reported in 1956 for an occurrence in Kazakhstan.

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.