Polybasite
Polybasite is a sulfosalt mineral of silver, copper, antimony and arsenic. Its chemical formula is Template:Chem2.
It forms black monoclinic crystals (thin, tabular, with six corners) which can show dark red internal reflections. It has a Mohs hardness of 2.5 to 3. It is found worldwide and is an ore of silver. The name comes from the number of base metals in the mineral.
Images
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Unusual polybasite specimen from Mayo Mining District, Yukon Territory, Canada.
