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The Mineral rhodochrosite
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Rhodochrosite is a very aesthetic and desirable mineral; its deep red and hot pink crystals are highly sought after. Of special note are the beautiful, intensely colored rhombohedral crystals that have come from the Sweet Home Mine in Colorado. This mine provided a fascinating discovery in the 1960's of some of the largest and most stunning Rhodochrosite crystals ever found. The largest Rhodochrosite crystal, called the "Alma King", is a single 15 cm crystal that was found in the Sweet Home Mine in 1992.
South Africa and Peru also produce intense red transparent scalenohedral crystals
that are also highly desirable to collectors. Some consider these Rhodochrosites, with the deep color, transparency, and well-formed crystals, to be the most beautiful of
all minerals. An interesting occurrence of this mineral is in Argentina, where
Rhodochrosite forms stalagmites and stalactites in the 13th century Inca Silver mines. They formed from precipitating water dripping from the manganese-rich rock inside the ancient mine tunnels, and kept on growing over the centuries into large stalagmites. These stalagmites are beautifully banded with concentric growth layer, and are often sliced and polished into slabs for collectors, and may be cut and polished for jewelry. Rhodochrosite belongs to the calcite group of minerals, a group of related carbonates that are isomorphous with one another. They are similar in many physical properties, and may partially or fully replace one another, forming a solid solution series. All members of the calcite group crystallize in the trigonal system, have perfect rhombohedral cleavage, and exhibit strong double refraction. When Rhodochrosite is exposed to the atmosphere, it may develop a thin film of manganese oxide on its surface. This may slightly darken the color of a specimen. Rhodochrosite sometimes alters into black manganese oxides (such as Pyrolusite, Manganite, and Psilomelane), and black manganese oxide stains are usually associated with Rhodochrosite. For additional information, see the gemstone section on Rhodochrosite. |
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Chemical Formula |
MnCO3 |
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Composition |
Manganese carbonate, sometimes containing some iron, magnesium, calcium, zinc, and cobalt.
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| Variable Formula |
(Mn,Fe,Mg,Ca,Zn,Co)CO3 |
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Color |
Bright red, hot pink, light pink, orange-red, brown, gray; may also be banded light and dark pink. |
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Streak |
White |
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Hardness |
3.5 - 4 |
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Crystal System |
Hexagonal |
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Crystal Forms
and Aggregates |
Mainly as rhombohedral and scalenohedral crystals. Dense clusters of rhombohedral crystals, as well as parallel bundles of scalenohedral crystals are common. An interesting form is in curved, saddle-shaped crystal groupings. Other habits are botryoidal, grainy, encrusting, radiating, massive, stalactitic, and as veins. |
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Transparency |
Transparent to opaque |
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Specific Gravity |
3.3 - 3.6 |
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Luster |
Vitreous to pearly |
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Cleavage |
1,3 - rhombohedral |
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Fracture |
Conchoidal to even |
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Tenacity |
Brittle |
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Other ID Marks |
1) Occasionally darkens upon exposure to air.
2) Occasionally fluorescent dark red.
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Complex Tests |
Slowly effervesces and dissolves in cold hydrochloric acid; this effect is much more pronounced in warm acid. |
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In Group |
Carbonates; Calcite Group |
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Striking Features |
Color combined with crystal form, hardness, and cleavage |
| Environment |
Hydrothermal veins associated
with Silver, Copper, and lead sulfides; may also be found in some
pegmatites. |
| Rock Type |
Igneous, Sedimentary, Metamorphic |
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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2 |
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Demand (1-3) |
1 |
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- Yellowish and gray banded, iron and zinc-rich variety of Rhodochrosite found in Capillitas, Catamarca, Argentina.
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Banded stalactitic Rhodochrosite from Catamarca, Argentina is used as a gemstone. It is carved into ornaments and figures, and polished into cabochons and beads for jewelry. Deeply colored Rhodochrosite crystals are highly desired by collectors, being one of the most popular minerals among high-end collectors. Rhodochrosite is also used as an ore of manganese.
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Rhodochrosite comes from a surprisingly varied amount of localities, although good specimens are far less common. Only localities that are well-known are mentioned here.
Banded Rhodochrosite stalagmites and stalactites come from the the Capillitas Mine, Catamarca, Argentina. Deeply colored and gemmy scalenohedral crystals come from Peru in the Huayllapon mine in the Pasto Bueno District, Ancash; the Huaron mine, Cerro de Pasco; and the Uchucchacua Mine, Oyon Province, Lima Dept. Curved, saddle-shaped crystal groupings were found at Huachocolpa, Huancavelca Dept., Peru.
In Mexico, good Rhodochrosite crystals come from Santa Eulalia, Chihuahua; and Cananea, Sonora, while pink rounded aggregates from Los Remedios Mine, Taxco, Guerro. One of the most famous forms of Rhodochrosite are the blood red, clear, scalenohedral crystals that come from the Kalahari
Manganese fields of South Africa, in Hotazel and the N'Chwaning Mines
of Kuruman. Dark red Rhodochrosite crystals were found in the Moanda Mine, Leboumbi-Leyou, Gabon. A recent supplier of outstanding Rhodochrosite specimens, including some very large rhombohedral crystals, is the Wutong Mine, Wuzhou, Guangxi Zhuang, China. Banded and botryoidal Rhodochrosite has
come from Japan in the Inakuraishi mine, Shiribeshi Province; and from
the Oppu mine in Nishimeya. Odd pseudomorphs of Rhodochrosite over organic material such as shells come from the Kerch peninsula, Crimea, Ukraine. A classic European locality for Rhodochrosite is the Wolf Mine in Herdorf, Siegerland, Germany, where Rhodochrosite formed in botryoidal aggregatess and in long, pointed, terminated crystals. Specimens from the Wolf Mine are very difficult to obtain. Light pink Rhodochrosite crystals have come from Kapnik, Maramures Co., Romania. The U.S. has several important Rhodochrosite localities The mines that have yielded the best crystals are in Colorado, particularly the Sweet Home Mine near Alma, Park Co., which is the most famous and coveted of Rhodochrosite localities. This mine was originally worked for the Silver it produced, but then stunning, bright red Rhodochrosite specimens started coming out of the mine. The mine was reopened in 1993 through 2004 strictly for Rhodochrosite specimen mining. Fine Rhodochrosite specimens have also been obtained in Colorado at Climax, Lake Co.; the Mt. Monarch Mine, Ouray Co.; the Eagle Mine, Gilman Co.; and the Silverton mining district (especially the American Tunnel/Sunnyside Mine) in San Juan Co. Large crystals and aggregates, pink in color, were found in Butte, Silver Bow Co., and in Phillipsburg, Granite Co., Montana. In Canada, dark reddish-brown Rhodochrosite rhombohedrons come from the famous locality of Mont Saint-Hilaire, Quebec. |
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Quartz, Chalcopyrite, Galena, Sphalerite, Pyrite, Fluorite, Tetrahedrite, Limonite, Pyrolusite, Manganite, Psilomelane
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Rhodonite - Harder (5½ - 6), crystallizes differently.
Pink Calcite - Strongly effervesces in hydrochloric acid.
Pink Dolomite - Usually in curved crystals.
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