RHODOCHROSITE

( Fr- rhodochrosite; Ger- Rhodochrosit; Nor- rhodokrositt; Rus- )

RHODOCHROSITE, MnCO₃.

A. Rhodochrosite (top left) honed surface (width - 8.4 cm) from Catamarca, Argentina. Canadian Museum of Nature. (© photo by Jeffrey A. Scovil)

B Rhodochrosite (bottom left) polished surface (width - 42.2 cm) from Catamarca, Argentina. Martin Zinn collection. (© photo by Jeffrey A. Scovil)

C. Rhodochrosite (right side) cabochons (largest one, greater axis - 6.0 cm). Rincon Minerals. (© photo by Jeffrey A. Scovil)

DESCRIPTION:
    Colors - rose red, pink, nearly white, and rarely yellowish or brownish, with most of the masses used as gemrocks exhibiting a variegated banding of white, pink and rose-red hues
    H. 3½ - 4
    S.G. 3.3-3.7
    Light transmission - translucent
    Luster - sub-vitreous to pearly
    Breakage - brittle, with fractures of gemrock massive variety typically uneven because they consist of innumerable cleavage surfaces of their component grains
    Miscellany - effervesces with warm dilute HCl.

OTHER NAMES:

Capillita (capillitita) - name sometimes applied to rhodochrosite from the Capillitas bed of Argentina, some of which is yellowish and gray bandedt; this name, apparently given before the material was known to be rhodochrosite, continues to be applied in some quarters.
Dialogite - continues to be used -- fortunately, less and less frequently -- as a synonym (discredited by CNMMN of IMA, 1962) for rhodochrosite.
Inca rose - see Rosa del Inca.
Manganese spar - rarely applied vernacular name that is based on its composition and formerly rather widely applied in the mining industry.
Raspberry spar - term used, usually as the result of translation of the sometimes applied German word Himberspat.
Rhodochrosite onyx - name sometimes used in lieu of Rosinca (q.v.).
Rosa del Inca (rose of the Incas) - designation frequently given in the marketplace, especially in Europe.
Rosinca - trade name given to some of the massive, typically banded rhodochrosite used as a gemrock. Although originally applied only to Argentinian rhodochrosite from the Catamarca Province, more recently some dealers have extended its application to similar rhodochrosite from other localities.
Sphaerodialogite - name sometimes given, especially in the past, to minute globules of rhodochrosite (see dialogite).

USES: Beads; cabochons and freeforms for pendants, brooches etc.; spheres, eggs, hearts and carvings; along with other gemrocks -- such as lapis lazuli, malachite and sugilite -- in some fine quality intarsia (gemstone inlay) pieces; also as specimens for use as show pieces. Both the larger gemstones and show pieces that are preferred by most people are those cut at approximately right angles to the lengths of the stalagmitic material -- see Figures A & B.

A large (10.875 kg = ~24 lb; greatest dimension 21.60 cm = ~ 8 1/2 in) carving "in the form of Lord Mahaveera, one of the ancient Indian sages who established the tenets of Jain Dharma" is described and shown in four photographs by Choudhary and Vyas (2011)

OCCURRENCES: Rhodocrosite has diverse geneses and occurrences. Most of the gemrock material of Argentina occurs as crusts or virtually complete fillings of preexisting fractures and as matrices of breccias that are spatially associated with zones of sulfide mineralization -- so, this rhodochrosite is, in a sense, a gangue mineral of sulfide deposits. Some of the finer quality masses, however, have so-to-speak stalagmitic growth patterns and shapes (see Figures A and B).

NOTEWORTHY LOCALITIES: Much of the massive gemrock rhodochrosite rough that is available in the marketplace comes from localities along the eastern side of the mountains of western Argentina; the copper-rich Capillitas bed in Andalgala County, Province of Catamarca has been especially productive. Shigley et al. (2000) tabulate localities and pertinent references for localities from which rhodochrosite used as a gemstone was recovered during the 1990s.; gemstone is used here because these figures include coarsely crystalline rhodochrosite -- i.e., gem mineral rhodochrosite -- that has been, for example, faceted.

REMARKS: The name rhodochrosite is from the Greek ῤοδοχρωϛ (ῤοδο - rose + χρωϛ - color). It is said the inca rose designation is based on the "fact" that some of it comes from stalctitic and stalagmitic growths in silver mines worked by the ancient Incas.

So far as I know, rhodochrosite has not been recorded as having been subjected to enhancement procedures. I suspect, considering its brittleness, that some lapidaries may have at least attempted to impregnate it.

As noted in the RHODONITE entry, for a while during the 1950s pink and black became so-to-speak fad colors, especially for men -- e.g., they/we wore pink shirts, black ties, etc., and, during that period, rhodonite, with its pink and black colors, was popular in jewelry such as tiepins and large cuff-links. However, a few pieces used during that period were fashioned from combinations of rhodochrosite and black onyx; and some rather attractive jewelry -- e.g., necklaces and bracelets -- made up of these two gemrocks continues to be marketed rather widely.

Rhodochrosite was approved as the official state mineral of Colorado by the state representatives and senators and signed by the governor on April 17, 2002. The rhodochrosite that led to this action is not, however, that herein described as gemrock; it is the "highly prized red rhodochrosite crystals from the Sweet Home mine [which] tops the list of desirable gems from the state" (Murphy and Modreski, 2002).

SIMULANTS:

Banded calcite -- e.g., onyx marble -- dyed pink. - [inferior hardness (H. 2) and lower specific gravity].

Talc-calcite aggregate - talc is the source of the color (i.e., the caclite is Manganese-free). - [lower S.G. (2.73)]. See Federov (2002).

REFERENCE: Saadi and Grasso, 1992.

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