RHODOCHROSITE  , a

mineral species consisting of manganese carbonate, MnCO3, 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 3.6o; the hardness is 4 . The colour is usually rose-red, but may sometimes be grey to brown . The name rhodochrosite, from the Greek /Soso-xptes (rose-coloured), 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 .