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The Mineral rhodochrosite
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Rhodochrosite is one of the prettiest and desirable of all minerals. Its deep red and hot pink crystals are extremely sought after and good crystals command extremely high prices. Especially desirable are the beautiful intensely colored rhombohedrons 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 scalenohedrons
that are extremely desirable to collectors and very highly priced. These Rhodochrosite
specimens are considered by many to be the most beautiful of
all minerals.
A very 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 layers and are often sliced and polished into slabs for collectors.
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 |
Occurs as rhombohedral and scalenohedral crystals. Dense clusters of rhombohedral crystals, as well as parallel bundles of scalenohedral crystals also occur. 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. |
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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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The banded stalactitic material from Catamarca, Argentina is used as a gemstone. It is carved into ornaments and figures, and polished into cabochons and beads for jewelry. Clear transparent Rhodochrosite is faceted into cut gems, but only for collectors. The deeply colored Rhodochrosite specimens are extremely desired by collectors and it is one of the most popular minerals among mineral enthusiasts. 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 in the Uchucchacua Mine, Oyon Province, Lima Dept. Curved, saddle-shaped crystal groupings come from Huachocolpa, Huancavelca Dept., Peru. In Mexico, good crystals come from both 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 come from the Moanda Mine, Leboumbi-Leyou, Gabon.
A recent supplier of outstanding Rhodochrosite specimens including some very large crystals is the Wudong Mine, Wuzhou, Guangxi Zhuang, China. Banded Rhodochrosite has
come from Japan in the Inakuraishi mine, Shiribeshi Province; and from
the Oppu mine, Aomori Prefecture. Very strange pseudomorphs of Rhodochrosite over organic material such as shells come from the Kerch peninsula, Crimea, Ukraine.
The most classic European locality is the Wolf Mine in Herdorf, Siegerland, Germany, where Rhodochrosite formed in unique botryoidal aggregatess and in long, pointed, terminated crystals. Specimens from the Wolf Mine are very difficult to obtain. Good, mostly pink specimens have also come from Europe in Kapnik, Romania.
The U.S. has many excellent Rhodochrosite localities, and mines yielding the most beautiful 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 until recently strictly for Rhodochrosite specimen production.
Fine 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 rhombohedrons come from the famous locality of Mont Saint-Hilaire, Quebec.
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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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