Arsenopyrite

Mineral(s): Arsenopyrite
Locality: Panasqueira, Covilhã, Portugal

If pyrite is "fool's gold", then you can say arsenopyrite is more like "fool's silver". In addition to the unmistakably silvery white color, this mineral also contains poisonous arsenic, hence its name {arseno}pyrite.

Here we have a ~1.5 cm group of lath-like arsenopyrite crystals with a high metallic luster, sitting on some muscovite mica. A slight spot of surface oxidation creates some bluish interference colors.