Rhodochrosite: Gemstone Information
Rhodochrosite is Mn2CO3 and forms pink, rose- or cherry-red transparentor translucent rhombohedral or scalenohedral crystals of the trigonal system with one direction of perfect cleavage. The hardness is 3.5–4 and the SG 3.70. The RI for the ordinary and extraordinary rays is 1.810 and 1.597,uniaxial negative with birefringence 0.201–0.220. Absorption bands can be seen in the visible at 565, 535 nm (both faint lines) and at 551 and 410 nm.Under both forms of UV there is a pink response from the mineral as a whole though individual specimens may not show much. Rhodochrosite occurs as a primary mineral in low- to moderate-temperature hydrothermal veins, also in metamorphic deposits and in carbonatites.
Exceptional transparent scalenohedra of magnificent orange-pink colour have been found comparatively recently from the Hotazel and N’Chwaning mines in the Kuruman area of Cape Province, South Africa; fine rose-red crystals are found at the Sweet Home mine, Alma, Park County, Colorado, USA,and from the Huallapon mine, Pasto Bueno, Ancash province, Peru. The Inakuraishi and Yakomo mines, Hokkaido, Japan, also produce cabochon quality material. Specimens from the Capillitas mine, San Luis, Catamarca province, Argentina, show characteristic banding from whitish calcite inclusions. Chatoyant rhodochrosite is reported from Kazakhstan;the eye is caused by an agate-like structure. Star rhodochrosite is reported from Russia and Argentina. A major paper on the Sweet Home mine can be found in The Mineralogical Record 29(4), 1998.