Rhodonite is a mineral with a hardness of 6 out of 10 on the Mohs scale of mineral hardness [?]. These Triclinicly structured gems are made of manganese silicate, their full chemical compound being (Mn,Fe,Mg,Ca)SiO3.
Rhodonite is a silicate of manganese-iron-magnesium, a mineral of the Pyroxene group, with a triclinic crystal system.
It appears as rare tabular crystals, sometimes with rounded edges and wrinkled faces. It sometimes occurs as distinct, translucent to semiopaque crystals, but more often it is in compact, granular, ot crystalline masses of a patchy, pink, flesh red or brownish red color, often with blackish veining or spiderweb bands due to oxidation of manganese.
Its color is reddish pink, with thin veins or patches of gray to black.
It is hard, heavy, fragile, and has perfect prismatic cleavage (almost at right angles). It is insoluble in acids (unlike similar, softer rhodocrosite), and fuses fairly easily to red or brown glass.
It is formed by metamorphism (with addition of silica) of other manganese minerals, probably including rhodocrosite. It is a mineral typical of metamorphism of impure limestones (manganese and silica-rich), which are often the result of contact metasonic processes (skarns).
It is fairly widespread, mainly found in Sweden, Great Britain, the Soviet republics, India, Australia, South Africa, the USA, and Mexico.
Crystals and masses of rhodonite are common at Langban and Pajsberg (Sweden) and in the Urals (Sverdlovsk district, Russia). It is also found at Broken Hill (Australia), Chikla (India), Simsio (Finland), in Arrow Valley (New Zealand), and in Brazil, South Africa, and Japan. Also at Saint-Marcel (Val d'Aosta), Monte del Forno, and in Valle di Scerscen (Sondrio) and at Libiola and Gambaresa (Genoa), all in Italy. Fine fowlerite crystals are found in crystalline marbles at Franklin, New Jersey (USA).
The zinc-bearing variety of rhodonite is called fowlerite, containing up to 10% zinc oxide, frequently cut as a gem.
Other varieties of rhodonite include: alagite - a dull red, or green, altered rhodonite; alajites - a Mexican name for altered rhodonite.
It is often confused with rhodocrosite, bustamite, and thulite.
Manganese spar is a general term for both minerals, rhodonite and rhodochrosite.
Rhodonite derives its name from the Greek "rhodon," meaning "pink" or "rose red" (like rhodocrosite).
The translucent to semiopaque polycrystalline form of rhodonite is cut en cabochon or shaped into beads, which can take a good polish. It is also used as an ornamental decorative element like inlay.
Rare transparent crystals have also been faceted into gems for collectors and connoisseurs. Facetable crystals are rare, but show a beautiful red, and have prismatic cleavage. Ornaments made of massive rhodonite are more common and are particularly handsome when they are veined by manganese oxides.
It is used in the art trade and occasionally as an ore of manganese.
Rhodonite has a somewhat low value compared with other ornamental materials, but faceted crystals are highly prized as collectors' pieces. It has neither been imitated nor produced synthetically.