Faceted rhodonite, 4.26 cts, 1.3 x 0.8 x 0.5 cm, Morro da Mina Mine, Conselheiro Lafaiete (old Queluz de Minas), Minas Gerais, Brazil. © Rob Lavinsky, www.iRocks.com. Used with permission.
Ranging in color from pink to a fine rose red, rhodonite is a popular material for jewelry and decorative objects. Faceted rhodonite has an intense, beautiful color, but this material has a reputation as one of the most difficult gemstones to cut.
| Data | Value |
|---|---|
| Name | Rhodonite |
| Crystallography | Triclinic. Crystals tabular; massive, cleavable, granular. |
| Refractive Index | 1.711-1.752 |
| Colors | Rose red, pink, brownish red; often veined by black Mn oxides. |
| Luster | Dull (massive) to vitreous. |
| Polish Luster | Vitreous. |
| Hardness | 5.5-6.5 |
| Wearability | Good to Poor |
| Wearability Notes | Good in aggregate; Poor in transparent stones |
| Fracture | Conchoidal |
| Specific Gravity | 3.57-3.76 (massive): 3.67 in crystals. See "Identifying Characteristics" below. |
| Birefringence | 0.011-0.014. See "Identifying Characteristics" below. |
| Cleavage | Perfect 1 direction |
| Luminescence | Dull red to inert. Medium dull red in SW (Hungary), dull deep red in LW (Langban. Sweden). Also thermoluminescence. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, UV-Short |
| Enhancements | Dyeing (rare). |
| Typical Treatments | Dyeing |
| Transparency | Transparent to opaque. |
| Absorption Spectrum | Broad band at 5480, strong narrow line at 5030, diffuse weak band at 4550. May also see lines at 4120 and 4080. |
| Phenomena | Chatoyancy (rare). |
| Formula | MnSiO3 (+ Ca to maximum of 20%). |
| Pleochroism | Weak, but may be distinct: yellowish red/pinkish red/pale yellowish red. |
| Optics | Biaxial (+), 2V=63-76°. Shadow edge at 1.73 in massive varieties. See “Identifying Characteristics” below. |
| Optic Sign | Biaxial + |
| Etymology | From the Greek rhodos for “rosy,” in allusion to the color. |
| Occurrence | In manganese-bearing ore bodies or in their vicinity. |
| Inclusions | May contain black dendritic inclusions of manganese oxide |
Rhodonite, Greystones Quarry, Lezant, Cornwall. Private collection. Photo by the University of Exeter. Licensed under CC By 2.0.
Perfect cleavage that develops extremely easily makes transparent, facetable rhodonite quite delicate. Thus, faceted stones are rare. However, gem carvers can make cabochons, goblets, figurines, and other objects from massive material with attractive black dendritic, “tree-like,” veins.
Rhodonite: Australia (beads, 15 mm). Photo © Joel E. Arem, PhD, FGA. Used with permission.
You may find cut bustamite gems erroneously labelled as rhodonites. They have a similar but paler color. However, bustamite’s distinctly lower refractive indices (RIs) should prove diagnostic.
Cut pyroxmangite gems also resemble rhodonites. However, their birefringence values differ.
Fowlerite is a zinc-bearing variety of rhodonite.
Some rhodonites found in Brazil may show chatoyancy.
Faceted rhodonites, Brazil. Gem cutting by Afonso Marques. Photo by Eurico Zimbres. Licensed under CC By-SA 3.0.
|
α |
β |
γ |
Birefringence |
Specific Gravity |
2V |
|
| Honshu, Japan |
1.726 |
1.731 |
1.739 |
0.013 |
3.57 |
64° |
| Pajsberg, Sweden |
1.720 |
1.725 |
1.733 |
0.013 |
3.62 |
75° |
| Broken Hill, New South Wales, Australia |
1.723-1.726 |
1.728-1.730 |
1.735-1.737 |
0.011-0.013 |
3.68-3.70 |
74° |
| General |
1.711-1.738 |
1.716-1.741 |
1.723-1.752 |
0.011-0.014 |
3.57-3.76 |
63-76° |
Rhodonite: Broken Hill, New South Wales, Australia (4.5). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Scientists have synthesized rhodonites for various projects, including research into their thermoluminescence.
You can find so-called “synthetic rhodonites” for sale in jewelry pieces. These appear most frequently as opaque pink to rose red beads with characteristic dendritic black veins rather than transparent faceted gems. (Oddly enough, some of this material features white bands more characteristic of rhodochrosite. Perhaps they’re mislabeled).
An online search for “synthetic rhodonites” doesn’t clarify whether these jewelry pieces contain actual lab-created rhodonite or just some other material intended to imitate or simulate the gem’s appearance. This may be another example of the term “synthetic” used in the more popular sense of just simply “not real.”
Rhodonites usually receive no treatments. Dyeing is rare.
Russia (Sverdlovsk) produces very fine and rich, massive, pink and rose-colored material. British Columbia, Canada yields fine rhodonite similar in appearance to the Russian material. However, the best material from British Columbia has a translucent, deep rose-pink color. Some fine, pink material from Bella Koola, British Columbia features black dendritic patterns.
Australia produces fine transparent crystals and massive material at Broken Hill, New South Wales. Gemmy rhodonite grains embedded in galena (lead sulfide) at this location are distinctive. Rhodonites can occur here with pyroxmangite and bustamite, which can grow in crystals up to 100 cm long!
Rhodonite crystal on crystalline galena matrix, Broken Hill, Yancowinna Co., New South Wales, Australia. © Rob Lavinsky, www.iRocks.com. Used with permission.
Other notable gem sources include:
Rhodonite parrot (Faberge) carving, St. Petersburg State Mining Institute. GV Plekhanov. Photo by Shakko. Licensed under CC By-SA 3.0.
Massive rhodonite pieces from various localities are available. However, extremely rare facetable gem material comes from crystals found primarily in Australia and Japan ranging in size from 2-3 carats. A few larger stones may exist.
Although pieces cut from massive material have greater wearability, both faceted gems and carved objects require special care. Due to rhodonite’s relatively low hardness, avoid mechanical cleaning such as steam or ultrasonic processes. Instead, use a soft brush, mild detergent, and warm water for cleaning. Store your rhodonites separately from other stones to avoid contact scratches. Use protective settings for your jewelry stones and avoid physical blows, due to their cleavage and fracture potential. Consult our gemstone jewelry cleaning guide for more recommendations.
“bg04_callyflore,” 25 x 18 mm rhodonite on adjustable 925 silver ring, by Imaginarium-Annelise. Licensed under CC By 2.0.
Adamantine. Silky. Greasy? Gemologists use these and other evocative terms to describe gemstone luster. This simply means how a gem’s surface…
IGS Become Member
.jpg){kind=link}