Rhodochrosite

Rhodochrosite forms in hydrothermal veins and fractures, often with silver ores, and as layered deposits in cavities, where it can build stalactites. Catamarca Province, Argentina (Capillitas), produces massive banded material and stalactites whose cross-sections show concentric "bull's-eye" patterns. The finest facetable crystals come from the Sweet Home Mine near Alma, Colorado; South Africa (Hotazel) yields deep red crystals, and other sources include Peru, Mexico, Montana, China, Japan, Romania and Russia.

Rhodochrosite is identified by its pink color, perfect cleavage in three directions, low hardness and very high birefringence, which causes strong doubling in transparent stones. It effervesces weakly in cold dilute hydrochloric acid (a destructive test). Rhodonite, a pink manganese silicate with a similar name, is harder and has darker, dendritic veining. Imitations include dyed calcite, talc-calcite aggregates and resin-bonded mineral powder layered to mimic banding (SG about 1.99, RI about 1.55). Synthetic rhodochrosite has appeared as beads and cabochons.

With a hardness of only 3.5 to 4 and perfect cleavage, rhodochrosite scratches and breaks easily; it is better suited to earrings, pendants and pins than to rings or bracelets. Avoid mechanical cleaning and any acid-containing cleaners; use a soft brush, mild detergent and warm water. A jeweler's torch can damage wax- or plastic-impregnated stones. Store it apart from other gems.

Johann Friedrich Ludwig Hausmann named the mineral in 1813 from the Greek words for "rose" and "coloring". At the Sweet Home Mine in Colorado, opened as a silver mine in 1873, rhodochrosite was at first disregarded; its crystals later became prized specimens. Rhodochrosite is the official state mineral of Colorado.