Rhodochrosite

Rhodochrosite, a mineral species consisting of manganese carbonate, MnCO 3, crystallizing in the rhombohedral system and isomorphous with calcite. It usually occurs as cleavable, compact or botryoidal masses, distinct crystals being somewhat rare; these often have the form of the primitive rhombohedron, parallel to the faces of which there are perfect cleavages. When pure, the mineral contains 47.7% of manganese, but this is usually partly replaced by varying amounts of iron, and sometimes by calcium, magnesium, zinc, or rarely cobalt (cobalt-manganese-spar). With these variations in chemical composition the specific gravity varies from 3.45 to 3.60; the hardness is 4. The colour is usually rose-red, but may sometimes be grey to brown. The name rhodochrosite, from the Greek p050-Xpc.s (rosecoloured), has reference to the characteristic colour of the mineral: manganese-spar and dialogite are synonyms. It is found in mineral veins with ores of silver, lead, copper, &c., or in deposits of manganese ore. Crystals have been met with in the mines at Kapnik-Banya and Nagyag near Deva in Transylvania and at Diez in Nassau, but by far the best specimens are from Colorado. The mineral is used to a limited extent in the manufacture of spiegeleisen and ferromanganese.