Rhodochrosite
Current inventory:  4 gems
 

  
Rhodochrosite is named from the Greek words rhodon for rose and chroma for color.

Discovered in 1813; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

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

Classification

Mineral Classification:

Carbonates

Strunz 8th Ed. ID:

5/B.02-50

Nickel-Strunz 10th Ed. ID:

5.AB.05

5 : CARBONATES (NITRATES)
A : Carbonates without additional anions, without H₂O
B : Alkali-earth (and other M²⁺) carbonates

Related to:

Calcite Group. Rhodochrosite-Siderite Series. Calcite-Rhodochrosite Series.

Members of Group:

Calcite Group: Calcite, Gaspéite, Magnesite, Otavite, Rhodochrosite, Siderite, Smithsonite, Spherocobaltite

Varieties:

Capillitite, Cobaltoan Rhodochrosite, Ponite, Sphaerodialogite, Zincorhodochrosite

Synonyms:

Carbonate of Manganese, Diallogite, Dialogite, Inca Rose, Manganese Spar, Raspberry Spar, Rhodochrolite, Rhodocrosite, Strömite, Torrensite, Villaurite

Crystal Data

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

Physical Properties

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.

Optical Properties

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

Occurances

Geological Setting:

A primary mineral in low- to moderate-temperature hydrothermal veins; in metamorphic deposits; common in carbonatites; authigenic and secondary in sediments; uncommon in granite pegmatites.

Common Associations:

Alabandite, Baryite, Braunite, Calcite, Dolomite, Fluorite, Friedelite, Garnet Group, Hausmannite, Manganite, Pyrite, Quartz, Rhodonite, Siderite, Sphalerite, Tephroite, Tetrahedrite

Common Impurities:

Fe, Ca, Mg, Zn, Co, Cd

Type Locality:

Cavnic Mine (Kapnikbánya), Cavnic (Kapnic; Kapnik), Maramures Co., Romania

Year Discovered:

1813

View mineral photos:

Rhodochrosite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

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.
 

    
Rhodochrosite gems for sale: