Tumbled rhodonite

Typically pink to rose-red with black dendritic or massive manganese-oxide veining; vitreous to pearly luster, triclinic crystals, imperfect cleavage, Mohs hardness 5.5–6.5, and specific gravity about 3.4–3.7.

Forms mainly by metamorphism or hydrothermal alteration of manganese-rich rocks, often in Precambrian terrains; the pictured piece is polished or naturally rounded, obscuring its original texture.

Used as a lapidary stone for cabochons, beads, carvings, and small polished specimens; historically, massive rhodonite has been used ornamentally and occasionally as a manganese ore.

Its dramatic pink-and-black pattern results from oxidation of manganese minerals, especially pyrolusite or braunite. The name derives from Greek rhodon, meaning “rose.”

Identify it by opaque rose-pink color, black manganese-oxide markings, relatively high density, and hardness below quartz; a streak and hardness test can help distinguish it from dyed stones. Common sources include Russia, Australia, Sweden, Peru, Brazil, and the United States, especially Massachusetts and Colorado.