Oval Portuguese-cut sapphirine, 1.09 cts, 7.1 x 5.7 mm, Sri Lanka. © The Gem Trader. Used with permission.
Sapphirines are durable but very rare gemstones. Although named after their typically sapphire-blue color, these gems can occur in different hues and display pleochroism, too.
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| Data | Value |
|---|---|
| Name | Sapphirine |
| Colors | Pale blue, bluish gray, greenish gray, green, purplish, brown; depth of blue color varies with Fe. Also, (rarely) purplish pink, red. |
| Formula |
Mg3.5Al9.0Si1.5O20 (+Fe). Complex substitution of Mg/Al/Si with charge balancing. Two polytypes:
|
| Etymology | In allusion to the stone’s often “sapphire blue” color. |
| Occurrence | In mineral veins or cavities in eruptive igneous rocks. |
| Fracture | Uneven to subconchoidal |
| Hardness | 7.5 |
| Cleavage | Indistinct |
| Wearability | Very Good |
| Crystallography | Monoclinic or triclinic; crystals tabular; usually granular or as disseminated grains. |
| Refractive Index | 1.701-1.723 |
| Birefringence | 0.006 |
| Dispersion | 0.019 |
| Luminescence | Inert, except for rare red gems. See "Identifying Characteristics" below. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, UV-Short |
| Absorption Spectrum | Not diagnostic |
| Pleochroism | Distinct: X = pinkish buff; yellowish; pale smoky brown; colorless: Y = sky blue; sapphire blue; greenish blue; Z = dark sky blue; sapphire blue. |
| Optics | a = 1.714-1.716; β = 1.719-1.721; γ = 1.720-1.723. Biaxial (-). See "Identifying Characteristics" for variations. |
| Optic Sign | Biaxial - |
| Luster | Vitreous |
| Specific Gravity | 3.4-3.5 |
| Transparency | Translucent to transparent |
Sapphirine and mica (var. muscovite) crystals. Beraketa, Bekily Department, Southwestern region, Tuléar Province (Toliara), Madagascar. Photo by Géry Parent. Licensed under CC By-SA 3.0.
Sapphirine has loaned its name to the sapphirine mineral supergroup, which contains three subgroups, including the sapphirine group.
Although sapphirines occur in transparent grains, facetable crystals are exceedingly rare.
Despite its name and most well-known color, sapphirine is a gem species distinct from sapphire. However, like sapphire, it too occurs in more colors than blue, albeit rarely. These colors include shades of violet, purple, green, pink, and brown. In 2007, a red variety was discovered in Tanzania. In addition, sapphirines can show very strong trichroic colors depending on the viewing angle.
Most rare gem-quality sapphirines are grayish blue, but rarer still are those that show different colors, like this dark brownish, somewhat purple specimen. 1.09 cts, oval brilliant cut, 6.9 x 5.5 mm, Sri Lanka. © The Gem Trader. Used with permission.
The term “sapphirine” has sometimes been applied incorrectly to blue specimens of chalcedony, crystalline quartz, and spinel. One specific usage in art history persists. The gemologist Fred Gray writes that the ancient Greeks created scarab-like seal rings and particularly favored light blue chalcedony. In recent times, this material received the French name of “sapphirine.”
Although the material is noted correctly as chalcedony in the museum listing, this rectangular prism is still referred to as “sapphirine chalcedony,” after the fashion of describing these antiquities. Minoan civilization, ca. 1900–1600 BCE, 1.65 cm x 0.75 cm x 0.65 cm. Bequest of Richard B. Seager, 1926. Metropolitan Museum of Art, New York. Public Domain.
Sapphirine’s refractive indices (RI) are close to those of idocrase. However, the former has a biaxial negative optic character. (Please note that idocrase may be anomalously biaxial). Sapphirines also exceed idocrase in specific gravity (SG).
An unusual, 1.54-ct, oval-cut, purplish-pink specimen from Sri Lanka (initially reported as idocrase) had the following properties:
The rare red sapphirine from Tanzania reportedly has the following luminescent properties under ultraviolet light (UV):
Serendibite, another rare mineral in the sapphirine supergroup, also occurs very rarely in gem-quality condition. Since the 1990s, faceted serendibites have begun to appear on the market. While sapphirines and serendibites may appear very similar and have overlapping properties, sapphirines usually have higher RIs and hardness.
A matched pair of oval mix-cut serendibites, black to very dark bluish green in strong transmitted light, 3.37 ctw, 6.4 x 8.1 mm, Myanmar. © The Gem Trader. Used with permission.
Scientists have synthesized sapphirines for geological research. However, there is no known jewelry use for this material.
No known gem treatments.
Madagascar and Sri Lanka are the principal producers of gem-quality sapphirines.
Other gem-quality sources include the following:
With a hardness of 7.5 and poor or indistinct cleavage, sapphirines would make good stones for everyday jewelry wear, especially if you like their classic blue appearance. Though small, most gem-quality stones are generally eye clean. These gemstones require no special care or cleaning methods.
Sapphirine, silver, and enamel brooch from the Ivan Britsyn workshop, St. Petersburg, Russia, 1908-17. Collection V. Kirichenko. Photo by Shakko. Licensed under CC By-SA 3.0.
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