Zunyite

Zunyite
Sharp, pyramids of brown-red zunyite from Silver City, Tintic District, East Tintic Mountains, Juab County, Utah, US (size: 5.5 x 5 x 3.5 cm)
General
Category	Sorosilicates
Formula (repeating unit)	Al13Si5O20(OH,F)18Cl
Strunz classification	9.BJ.55
Crystal system	Isometric
Crystal class	Hextetrahedral (43m) H-M symbol: (43m)
Space group	F43m
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
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

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

1. Handbook of Mineralogy
2. Mindat.org
3. Web Mineral

• Glendale Community College; retrieved March 26, 2005.
• Euromin; retrieved March 26, 2005.