Round brilliant rhodolite, 16.27 cts, 15.5 mm, Tanzania. © The Gem Trader. Used with permission.
Rhodolites are purplish red garnets, a blend between almandine and pyrope in composition. These durable gems have become popular jewelry stones.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
| Data | Value |
|---|---|
| Name | Rhodolite Garnet |
| Is a Variety of | Almandine-Pyrope |
| Crystallography | Isometric |
| Refractive Index | 1.745-1.761 |
| Colors | Purplish red, red-purple, reddish purple. |
| Luster | Vitreous |
| Hardness | 7-7.5 |
| Fracture | Conchoidal |
| Specific Gravity | 3.79-3.80 (Tanzania); 3.83-3.89 (Zimbabwe); 3.84-3.89 (North Carolina). |
| Birefringence | None |
| Cleavage | None |
| Dispersion | 0.026 |
| Luminescence | None |
| Luminescence Present | No |
| Transparency | Transparent |
| Absorption Spectrum | Rhodolites show an almandine spectrum. Almandines have a distinctive, diagnostic absorption spectrum: A band 200 Å wide at 5760 (strong) and also strong bands at 5260 and 5050. Lines may appear at 6170 and 4260. With a spectroscope, you’ll see this pattern of 3 (or sometimes 5) bands in all almandines as well as most garnets with a significant almandine component. |
| Phenomena | Asterism, color change (both rare) |
| Birthstone | January |
| Pleochroism | None |
| Optics | N = 1.750-1.760 (Zimbabwe); 1.760-1.761 (North Carolina); 1.745-1.760 (Tanzania). |
| Formula | (Fe,Mg)3Al2Si3O12 |
| Etymology | Some scholars believe the name comes from the Greek rhodon, meaning “rose.” Other believe it came from a comparison to the rhododendron flower (whose name also comes from rhodon). |
| Inclusions | Oriented needle-like rutile, apatite crystals (North Carolina), and other inclusions like those in almandines. See "Identifying Characteristics" in the almandine gem listing. |
Matched rhodolites, 2.52 cts and 6.5 mm each, Tanzania. Photo © Joel E. Arem, PhD, FGA. Used with permission.
Although gemology texts have traditionally described rhodolites as one part almandine and two parts pyrope, garnets never have just two species in the mix. Small amounts of other garnet species, like grossular and spessartite, are always present in rhodolites. In fact, the higher the spessartite content, the lighter the rhodolite’s color. Nevertheless, the purplish red hue distinguishes rhodolites, not the tone or saturation levels.
Rhodolites can range in color from purplish red to reddish, almost pure purple, and specimens that resemble amethyst in color have been found in North Carolina and India. However, most gem-quality rhodolites have a purplish red color.
These matched oval, brilliant-cut rhodolites (6.56 cts, 10 x 8 mm, Orissa, India) have a deeper purple, less reddish color than most rhodolites. © The Gem Trader. Used with permission.
Not all purplish red garnets are rhodolites. A chemical analysis is required first to determine if a stone of that color is an almandine-pyrope mix.
Rhodolite gemstones are affordable and make great options for engagement rings as well as January birthstone jewelry.
A sweet toi et moi setting nestles a pear-cut rhodolite garnet next to a ruby in a delicate, wavy, yellow gold engagement ring. © CustomMade. Used with permission.
Rhodolites may have a strong to very strong reaction to magnetism. Although testing magnetic reactions isn’t a basis for a positive gem identification, it can help make quick separations between gems of similar appearance.
Gem-quality rhodolites typically have no eye-visible inclusions and, therefore, usually receive the highest clarity grade for Type II gems, which includes all garnets.
Material from the North Pare Mountains, Tanzania, (N = 1.765; SG = 3.88) may show a color change, blue in daylight to purplish red in incandescent light, similar to alexandrite. Note that some color change garnets mined in the Morogoro region of Tanzania in 1988 were long considered rhodolites but were later revealed to be pyrope-spessartite, a more typical variety for color change garnets.
Rare examples of asterism (the “star stone” effect) may occur in rhodolites from East Africa.
Star rhodolite, 61.84 cts, 23.53 x 18.86 x 12.26 mm, Africa. Photo courtesy of liveauctioneers.com and Kissing Auction.
Geologists have synthesized almandine-pyrope garnets via the hydrothermal method for research purposes. While some of this material may appear for sale as gemstones, this process is too expensive for regular commercial rhodolite production. With rhodolites of exceptional clarity, gemologists should look for telltale signs of hydrothermal growth, such as seed plates, under high magnification.
See the “Synthetics” section in the main garnet gem listing for more information on other lab-created garnet varieties.
You may find many so-called “synthetic rhodolite” gems for sale online. However, these products may actually be simulants, such as glass or colored cubic zirconia (CZ) lookalikes, rather than synthetics. In these cases, merchants use the term “synthetic” in the popular sense, meaning “not real,” instead of the gemological sense of a lab-created analogue to a natural gem.
Rhodolites typically receive no gem treatments. However, in an experiment from 1997, rhodolites turned orange and brownish red and even developed a metallic coating from heating.
The principal sources for gem-quality rhodolites are Brazil, India, Madagascar, Sri Lanka, Tanzania, and Zimbabwe.
2.15-ct rhodolite cabochon, 8 x 6 x 3 mm, Madagascar. Photo courtesy of liveauctioneers.com and Jasper52.
Other notable gem sources include the following:
Fragments of rhodolite crystals from Cowee, North Carolina. Photo by Ewm1np2b. Licensed under CC By-SA 3.0.
The type locality for rhodolite (Cowee Creek, Macon County, North Carolina) usually produces very small stones, 1-2 carats and under. However, finds in Africa have yielded gems over 75 carats.
With no cleavage and a hardness of 7-7.5, rhodolites make durable stones for any type of jewelry setting. However, take care when cleaning these gems. Although a rhodolite may have no eye-visible inclusions, smaller inclusions may burst due to extreme heat or ultrasound and fracture the gem. Avoid mechanical cleaning systems and stick to a soft brush, mild detergent, and warm water, instead.
See our gemstone jewelry care guide for more recommendations.
14k gold ring with marquise-cut rhodolites, 0.60 ctw, and diamonds, 0.20 ctw, in a floral design. Photo courtesy of liveauctioneers.com and I&S Fine Auctions.
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