Rhodonite

Rhodonite is a manganese inosilicate, with the formula (Mn, Fe, Mg, Ca)SiO3, and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. The term rhodonite was first introduced by Germar. from Ancient Greek ῥόδον (rhódon) 'rose'. It commonly occurs as cleavable to compact masses with a rose-red color often tending to brown due to surface oxidation. The rose-red hue is caused by the manganese cation (Mn2+).

Rhodonite crystals often have a thick tabular habit, but are rare. It has a perfect, prismatic cleavage, almost at right angles. The hardness is 5.5–6.5, and the specific gravity is 3.4–3.7; luster is vitreous, being less frequently pearly on cleavage surfaces. The manganese is often partly replaced by iron, magnesium, calcium, and sometimes zinc, 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. The inosilicate (chain silicate) structure of rhodonite has a repeat unit of five silica tetrahedra.