sylvanite

{{Infobox mineral | name = Sylvanite | category = Telluride mineral | boxwidth = | boxbgcolor = | image = Sylvanite ((Au,Ag)2Te4), Cripple Creek Diatreme.jpg | imagesize = 300 | caption = Sylvanite from the Cripple Creek mining district | formula = | IMAsymbol = Syv | molweight = 429.89g/mol | strunz = 2.EA.05 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P2/c | color = Silver-grey, silver-white | habit = Massive to crystalline | twinning = | cleavage = Perfect on the {010} | fracture = Uneven | tenacity = Brittle | mohs = 1.5–2 | luster = Metallic | polish = | refractive = | opticalprop = Anisotropic | birefringence = | dispersion = | pleochroism = None | fluorescence= None | absorption = | streak = Steel grey | gravity = 8.2 | density = 8.1 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque | other = | references = }} Sylvanite or silver gold telluride, chemical formula , is the most common telluride of gold.

==Properties== The gold:silver ratio varies from 3:1 to 1:1. It is a metallic mineral with a color that ranges from a steely gray to almost white. It is closely related to calaverite, which is more purely gold telluride with 3% silver. Sylvanite crystallizes in the monoclinic 2/m system. Crystals are rare and it is usually bladed or granular. It is very soft with a hardness of 1.5–2. It has a high relative density of 8–8.2. Sylvanite is photosensitive and can accumulate a dark tarnish if it is exposed to bright light for too long.