Krennerite

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Krennerite
Krennerite-118304.jpg
Krennerite from the Cresson Mine, Cripple Creek, Colorado (about 5 mm).
General
Category Telluride mineral
Formula
(repeating unit)
AuTe2 to Au3AgTe8
Strunz classification 2.EA.15
Crystal system Orthorhombic
Crystal class Pyramidal (mm2)
Space group Orthorhombic
H-M symbol: (mm2)
Space group: Pma2
Identification
Color Silver white to brass yellow (tarnish?) - creamy white (polished section)
Crystal habit Massive to crystalline with short striated prismatic crystals
Cleavage Perfect on {001}
Fracture Subconchoidal - uneven
Tenacity Brittle
Mohs scale hardness 2.5
Luster High metallic
Streak greenish grey
Diaphaneity opaque
Specific gravity 8.62
Optical properties Anisotrophism strong
Refractive index Opaque
Pleochroism weak
Ultraviolet fluorescence None
References [1][2][3]

Krennerite is an orthorhombic gold telluride mineral which can contain variable amounts of silver in the structure. The formula is AuTe2 varying to (Au0.8,Ag0.2)Te2. 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).[3]

See also[edit]

References[edit]

Krennerite in a quartz vein, Cresson Mine, Cripple Creek, Colorado. Specimen size 3.0 x 2.7 x 2.5 cm. See infobox for detail photo.