Copper and mispickel are mined only in small quantities.
Mines of iron, manganese, and especially of mispickel, are worked, and there are stone-quarries and productive saltmarshes.
Mispickel occurs in metalliferous veins with ores of tin, copper, silver, &c. It is occasionally found as embedded crystals, for example, in serpentine at Reichenstein, Silesia.
The presence of copper, nickel and arsenic is possibly due in many cases to traces of kindred minerals, like chalcopyrite, pentlandite and mispickel.
Arsenides, Arsenites, &c. - Several iron arsenides occur as minerals; lolingite, FeAs 2, forms silvery rhombic prisms; mispickel or arsenical pyrites, Fe2AsS2, is an important commercial source of arsenic. A basic ferric arsenite, 4Fe2O3 As2O3.5H 2 O, is obtained as a flocculent brown precipitate by adding an arsenite to ferric acetate, or by shaking freshly prepared ferric hydrate with a solution of arsenious oxide.