Rhodochrosite
Rhodochrosite is a member of the Calcite Group of minerals that includes Calcite, Gaspeite, Magnesite, Otavite, Rhodochrosite, Siderite, Smithsonite and Spherocobaltite. Although Rhodochrosite is found in shades of pink, red and orangish pink, each of these colors seems unique in the gem world.
Some say the world’s finest Rhodochrosite comes from the Sweet Home Mine near Alma, Colorado. The rare and spectacular pink to red crystals are in such high demand for mineral collections that faceted gems are even rarer. The Sweet Home Mine was recently closed, making mineral specimens and faceted gems from this location especially rare.
Other sources of Rhodochrosite include Argentina, Japan, Peru, Russia and South Africa. Agentina produces beautiful pink cabochons with intricate color designs. Peru has small beautiful crystals that could be faceted, but the gems would be very small. The Hotazel Mine of the Kalahari Manganese fields in South Africa produces deep red crystals suitable for faceting. Rhodochrosite from Russia can be found as deep pink to red cabochons and rarely as faceted gems. The cabochons from Argentina are quite common. Cabochons from Japan and Russia are rare. Faceted gems from the Sweet Home Mine in Colorado and the Hotazel Mine in South Africa are very rare and in very high demand.
| Chemical Formula: | Mn2+CO3 |
| Manganese Carbonate | |
| Molecular Weight: | 114.95 gm |
| Composition: | Manganese | 47.79 % | Mn | 61.71 % | MnO |
| Carbon | 10.45 % | C | 38.29 % | CO2 | |
| Oxygen | 41.76 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Trigonal – Hexagonal Scalenohedral |
| Crystal Habit: | Crystals rhombohedral {1011} or less commonly {0112}, then frequently rounded and composite; scalenohedral rare; thick tabular {0001}; prismatic [0001]. {1120} and {2131} often striated [1101]. Massive, coarsely granular; compact; columnar; crusts; stalactitic (with zoned growth rings); botryoidal. |
| Twinning: | On {1012}, contact and lamellar, then flattened |
| Cleavage: | Perfect on {1011}; perfect rhombohedral. Parting on {0112} at times. Translation gliding with T{0001}, t[1010]. |
| Fracture: | Irregular/Uneven, Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 3.5 – 4.0 |
| Density: | 3.40 – 3.60 (pure = 3.70) (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Other: | Slightly soluble in water with the solubility rate increasing with the presence of CO2. Soluble with effervescence in warm acids. |
| Color: | Pink, rose-red, cherry-red, yellow, yellowish gray, cinnamon-brown, may be banded; pale rose to colorless in transmitted light. Reds occur when the mineral has minimal iron content. |
| Transparency: | Transparent to Translucent |
| Luster: | Vitreous; Pearly in aggregates |
| Refractive Index: | 1.596 – 1.816 Uniaxial ( – ) |
| Birefringence: | 0.2180 |
| Dispersion: | n/a |
| Pleochroism: | Weak, Faint; deep red colored material may be faintly dichroic with absorption O greater than E |
