Krennerite

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 ([Au_0.77Ag_0.24]Te₂).^[2] Both of the chemically similar gold-silver tellurides, calaverite and sylvanite, are in the monoclinic crystal system, whereas krennerite is orthorhombic.

Krennerite
Krennerite in a quartz vein, Cresson Mine, Cripple Creek, Colorado
General
Category	Telluride mineral
Formula	AuTe2 to Au3AgTe8
IMA symbol	Knn[1]
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	[2][3][4]

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

• List of minerals
• List of minerals named after people