krennerite

{{Infobox mineral | name = Krennerite | category = Telluride mineral | boxwidth = | boxbgcolor = | image = Krennerite-118303.jpg | imagesize = 260px | caption = Krennerite in a quartz vein, Cresson Mine, Cripple Creek, Colorado | formula = AuTe2 to Au3AgTe8 | IMAsymbol = Knn | molweight = | strunz = 2.EA.15 | system = Orthorhombic | class = Pyramidal (mm2) | symmetry = Orthorhombic H-M symbol: (mm2) Space group: Pma2 | color = Silver white to brass yellow (tarnish?) – creamy white (polished section) | habit = Massive to crystalline with short striated prismatic crystals | twinning = | cleavage = Perfect on {001} | fracture = Subconchoidal – uneven | tenacity = Brittle | mohs = 2.5 | luster = High metallic | polish = | refractive = Opaque | opticalprop = Anisotrophism strong | birefringence = | dispersion = | pleochroism = weak | fluorescence= None | absorption = | streak = greenish grey | gravity = 8.62 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = opaque | other = | references = }} 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). 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.