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Krennerite

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Krennerite
Krennerite in a quartz vein, Cresson Mine, Cripple Creek, Colorado
General
CategoryTelluride mineral
Formula
(repeating unit)
AuTe2 to Au3AgTe8
IMA symbolKnn[1]
Strunz classification2.EA.15
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
Space groupOrthorhombic
H-M symbol: (mm2)
Space group: Pma2
Identification
ColorSilver white to brass yellow (tarnish?) – creamy white (polished section)
Crystal habitMassive to crystalline with short striated prismatic crystals
CleavagePerfect on {001}
FractureSubconchoidal – uneven
TenacityBrittle
Mohs scale hardness2.5
LusterHigh metallic
Streakgreenish grey
Diaphaneityopaque
Specific gravity8.62
Optical propertiesAnisotrophism strong
Refractive indexOpaque
Pleochroismweak
Ultraviolet fluorescenceNone
References[2][3][4]

Krennerite is an orthorhombic gold telluride mineral which can contain variable amounts of silver in the structure. The formula is AuTe2, but specimen with gold substituted by up to 24% with silver have been found ([Au0.77Ag0.24]Te2).[2] Both of the chemically similar gold-silver tellurides, calaverite and sylvanite, are in the monoclinic crystal system, whereas krennerite is orthorhombic.

The color varies from silver-white to brass-yellow. It has a specific gravity of 8.62 and a hardness of 2.5. It occurs in high temperature, hydrothermal environments.

Krennerite was discovered in 1878 near the village of Săcărâmb, Romania, and first described by the Hungarian mineralogist Joseph Krenner (1839–1920).[4]

See also

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References

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  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 "Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2021-03-03. Retrieved 2017-05-09.
  3. ^ Krennerite Mineral Data on Webmineral
  4. ^ a b Krennerite: Krennerite mineral information and data om Mindat