Zunyite

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Zunyite
Zunyite-199876.jpg
Sharp, pyramids of brown-red zunyite from Silver City, Tintic District, East Tintic Mountains, Juab County, Utah, USA (size: 5.5 x 5 x 3.5 cm)
General
Category Sorosilicates
Formula
(repeating unit)
Al13Si5O20(OH,F)18Cl
Strunz classification 09.BJ.55
Crystal symmetry Isometric, 4 3m
Unit cell a = 13.8654 - 13.8882 Å; Z = 4
Identification
Color Grayish white, flesh-red; colorless in thin section
Crystal habit Crystalline - occurs as well-formed fine sized crystals
Crystal system Isometric - Hextetrahedral
Twinning On {111}, contact and penetration
Cleavage Good on {111}
Fracture Uneven
Tenacity Brittle
Mohs scale hardness 7
Luster Vitreous
Streak White
Diaphaneity Transparent to translucent with inclusions
Specific gravity 2.874(5) (meas.) 2.87 - 2.90 (calc.)
Optical properties Isotropic
Refractive index n = 1.592 - 1.600
Other characteristics May fluoresce red under UV
References [1][2][3]

Zunyite is a sorosilicate mineral, Al13Si5O20(OH,F)18Cl, composed of aluminium, silicon, hydrogen, chlorine, oxygen, and fluorine.

Occurrence[edit]

Glassy, translucent, gray-tan, pseudohexagonal zunyite crystals on a milky quartz matrix. From the Big Bertha Mine, Dome Rock Mountains, La Paz County, Arizona (size: 3.3 x 3.2 x 2.8 cm))

Zunyite occurs in highly aluminous shales and hydrothermally altered volcanic rocks. It occurs in association with pyrophyllite, kaolinite, alunite, diaspore, rutile, pyrite, hematite and quartz.[1]

It was discovered in 1884, and named for its discovery site, the Zuni mine in the Silverton District, San Juan County, Colorado.[2]

References[edit]