Cobaltite

Lore & Background

The name 'cobaltite' traces back to the element cobalt, which itself comes from the German term Kobold, meaning an 'underground spirit' or 'goblin.' This connection arose because cobaltite and other cobalt ores resisted medieval smelting methods, often producing foul-smelling, poisonous fumes—hence the notion of 'bewitched' minerals. A variety containing much iron replacing cobalt, known as ferrocobaltite (German: Stahlkobalt), was found at Siegen in Westphalia. In India, crystals from Khetri in Rajasthan were used under the name sehta by local jewellers to produce a blue enamel on gold and silver ornaments.

Reader's Guide

Cobaltite is mined as a significant source of the strategically important metal cobalt, despite its rarity. It occurs in high-temperature hydrothermal deposits and contact metamorphic rocks, often alongside magnetite, sphalerite, chalcopyrite, skutterudite, allanite, zoisite, scapolite, titanite, and calcite, as well as numerous other Co–Ni sulfides and arsenides. To separate cobaltite from other minerals, selective, pH-controlled flotation methods are used, with cobalt recovery usually involving hydrometallurgy. It can also be processed with pyrometallurgical methods, such as flash smelting.

Secondary weathering incrustations of erythrite, a hydrated cobalt arsenate, are common. Major deposits are found in Sweden, Norway, Germany, Cornwall (England), Canada, La Cobaltera (Chile), Australia, the Democratic Republic of the Congo, and Morocco. Crystals from Khetri in Rajasthan, India, were used under the name sehta by Indian jewellers to produce blue enamel on gold and silver ornaments.