Gahnite
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Gahnite
Gahnite
Gahnite.jpg
General
CategoryOxide minerals
Spinel group
Spinel structural group
Formula
(repeating unit)
ZnAl2O4
Strunz classification4.BB.05
Crystal systemCubic
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFd3m
Identification
ColorDark green, bluish green, blue to indigo, yellow to brown
Crystal habitTypically octahedra, rarely as dodecahedra also massive to granular
TwinningCommon on [111] produces striations
CleavageIndistinct parting on [111]
FractureConchoidal, uneven
Mohs scale hardness7.5-8.0
LusterVitreous
StreakGrey
DiaphaneityTranslucent to nearly opaque
Specific gravity4.38-4.60
Optical propertiesIsotropic
Refractive indexn = 1.79-1.80
References[1][2][3]

Gahnite, ZnAl2O4, is a rare mineral belonging to the spinel group. It forms octahedral crystals which may be green, blue, yellow, brown or grey. It often forms as an alteration product of sphalerite in altered massive sulphide deposits such as at Broken Hill, Australia. Other occurrences include Falun, Sweden where it is found in pegmatites and skarns, Charlemont, Massachusetts; Spruce Pine, North Carolina; White Picacho district, Arizona; Topsham, Maine; and Franklin, New Jersey in the United States.[1][2]

It was first described in 1807 for an occurrence in the Falu mine, Falun, Dalarna, Sweden, and named after the Swedish chemist, Johan Gottlieb Gahn (1745-1818), the discoverer of the element manganese.[2][3] It is sometimes called zinc spinel.

References


  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

Gahnite
 



 



 
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