Gahnite

(repeating unit)ZnAl2O4IMA symbolGhn[1]Strunz classification4.BB.05Crystal systemCubicCrystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)Space groupFd3mIdentificationColorDark green, bluish green, blue to indigo, yellow to brownCrystal habitTypically octahedra, rarely as dodecahedra also massive to granularTwinningCommon on [111] produces striationsCleavageIndistinct parting on [111]FractureConchoidal, unevenMohs scale hardness7.5–8.0LusterVitreousStreakGreyDiaphaneityTranslucent to nearly opaqueSpecific gravity4.38–4.60Optical propertiesIsotropicRefractive indexn = 1.79–1.80References[2][3][4]

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; and, in the United States, Charlemont, Massachusetts; Spruce Pine, North Carolina; White Picacho district, Arizona; Topsham, Maine; and Franklin, New Jersey.[2][3]

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.[3][4] It is sometimes called zinc spinel.

See also

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Gahnite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 14 March 2022.
  3. ^ a b c Gahnite, Mindat.org
  4. ^ a b http://webmineral.com/data/Gahnite.shtml Webmineral
Wikimedia Commons has media related to Gahnite.


  • v
  • t
  • e