Native arsenic. Arsenic in its native form, as here, is rare. It is more commonly found and mined as salts and minerals. This polished slab, from the St. Andreasberg mines in Germany, shows patterns in various shades of grey. Arsenic, a toxic metalloid element, has many industrial uses, including in agricultural insecticides, electric circuitry, and fireworks. This sample measures 120 millimetres from top to bottom.