Silicate of manganese. .
Crystal system Triclinic.
Appearance Rthodonite sometimes occurs as distinct, translucent to semiopaque crystals. but more often it is in compact, crystalline masses of a patchy, pink, tlesh red or brownish red color. often with blackish veining due to oxidation ot manganese.
Physical properties It has a hardness oi 5.5—6.5. The density ranges from 3.40 to 330 g/cma. The refractive indices vary between nw 1.733.11 ne 1.44 and ne 1.716, nw 1.?28 (the optic sign therefore changing from negative to positive), but the massive material normally gives one value, of about 1.73.
Genesis It is formed by metamorphism (with addition of silica) of other manganese minerals, probably including rhodoohrosite (MnC03).
Occurrence It is fairly widespread. mainly found in Sweden, Great Britain. the Soviet Union, lndia, Australia, South Africa. the United States, and Mexico.
Like rhodochrosite, its name is derived from the Greek root. rhodon, meaning "pink."
Appearance The color is reddish pink, with thin veins or patches of gray to black. The translucent to semiopaque polycrystalline form is cut en cabochon or shaped into beads, which can take a good polish. Flare transparent crystals have also been faceted into gems for collectors and connoisseurs. The individual crystals have prismatic cleavage.
Distinctive features It is distinguished from rhodochrosite by its greater hardness and the fact that it is not attacked by hydrochloric acid.
Occurrence It comes mainly from the Soviet Union, India, Australia. and the United States.
Value Somewhat low compared with other ornamental materials.
Simutante and synthetics it has neither been imitated nor produced synthetically.