1911 Encyclopædia Britannica/Rhodonite

RHODONITE, a member of the pyroxene group of minerals, consisting of manganese metasilicate, MnSiO₃, and crystallizing in the anorthic system. It commonly occurs as cleanable to compact masses with a rose-red colour; hence the name, from the Greek ῥόδον (a rose). Crystals often have a thick tabular habit; there are perfect cleavages parallel to the prism faces with an angle of 87° 311/2′. The hardness is 51/2–61/2, and the specific gravity 3·4–3·68. The manganese is often partly replaced by iron and calcium, which may sometimes be present in considerable amounts; a greyish-brown variety containing as much as 20% of calcium oxide is called “bustamite”; “fowlerite” is a zinciferous variety containing 7% of zinc oxide. Rhodonite is a mineral liable to alteration, with the formation of manganese carbonate, hydrous silicate or oxides. The compact material, which is cut and polished for ornamental purposes, is often marked in a striking manner by veins and patches of these black alteration products. At Syedelnikova, near Ekaterinburg in the Urals, compact material of a good colour occurs in a clay-slate and is extensively quarried: boulders of similar material found at Cummington in Massachusetts (“cummingtonite”) have also been worked as an ornamental stone. In the iron and manganese mines at Pajsberg near Filipstadt and Långban in Vermland, Sweden, small brilliant and translucent crystals (“pajsbergite”) and cleavage masses occur. Fowlerite occurs as large, rough crystals, somewhat resembling pink felspar, with franklinite and zinc ores in granular limestone at Franklin Furnace in New Jersey.