0.80-ct jeremejevite, mined in the Erongo Mountains, Namibia. Photo © Claradyn Venter. Used with permission.
Jeremejevite would make a durable and attractive jewelry stone, but this rare mineral occurs even more rarely as facetable material. Recently, new sources have been discovered, but jeremejevite remains mainly a prized collector’s gem.
| Data | Value |
|---|---|
| Name | Jeremejevite |
| Crystallography | Hexagonal; crystals elongated and tapering; also small grains, acicular, ball-shaped aggregates. |
| Refractive Index | 1.637-1.653 |
| Colors | Colorless, greenish, pale blue-green, blue, pale yellow-brown, light yellow, golden yellow, and violet (very rare). May show color banding. |
| Luster | Vitreous. |
| Hardness | 6.5-7.5 |
| Fracture | Conchoidal |
| Specific Gravity | 3.28-3.31 |
| Birefringence | 0.007-0.013. |
| Cleavage | None |
| Dispersion | 0.009 (C-F) |
| Luminescence | None. |
| Luminescence Present | No |
| Transparency | Transparent. |
| Absorption Spectrum | Vague absorption band at about 5000. |
| Formula | Al6B5O15(OH,F)3 |
| Pleochroism | Blue material: light cornflower blue/colorless to light yellow (Namibian material). Also, yellow material: light yellow/colorless. |
| Optics | e = 1.637-1.644; o = 1.644-1.653. Uniaxial (-). Cores of crystals sometimes biaxial (from Russia), 2V = 0-50°. Biaxial rims also sometimes observed in Namibian material. |
| Optic Sign | Uniaxial -, Biaxial - |
| Etymology | Named after Pavel V. Jeremejev, Russian mineralogist and engineer. |
| Occurrence | Granite pegmatites. |
| Inclusions | Feathers, fingerprints (sometimes fluid-filled), multi-phase inclusions, crystals, growth lines. |
Light yellow, cushion-cut jeremejevite, 5.83 cts, 10.2 x 9.0 x 8.0 mm, Myanmar. © ARK Rare Gems. Used with permission.
Jeremejevite: Nerchinsk, Siberia, Russia (0.5, 0.4). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Discovered in Russia in 1883, jeremejevite (pronounced yer-ah-mee-YAY-vite) was long available only as microscopic grains. In the 1970s, this rare borate mineral was discovered in large, facetable crystals in Namibia. However, lapidaries cut very few gems from this material, because mineral collectors prized these specimens.
Recent discoveries of this gemstone at additional sites in Namibia and other locations have made available more facetable material in a wider range of pale colors. In addition to colorless, light blues, and yellow-browns, jeremejevites can show greenish, light yellow, golden yellow, and even violet colors. (Its light blue to blue-green hues have drawn comparisons to aquamarines).
Golden jeremejevites, up to 2.6 cm in length, Mogok, Myanmar. © Rob Lavinsky, www.iRocks.com. Used with permission.
With a hardness of 6.5 to 7.5 and no cleavage, jeremejevite could make a suitable jewelry stone selection. However, it remains rare and — for the time being — largely unknown to jewelry enthusiasts.
Jeremejevites are piezoelectric. This means these gems generate electricity when placed under pressure.
In addition to having overlapping ranges of color and hardness with aquamarine and quartz, jeremejevite crystals, particularly in prismatic hexagonal shapes, can resemble these other gem species. However, jeremejevites have a higher refractive index (RI) range and specific gravity (SG).
Jeremejevite rough and cut set. Crystal: 4.7 x 0.3 x 0.2 cm; narrow emerald-cut gem: 1.13 cts, 11.05 x 3.79 mm. Mile 72, Cape Cross area, Swakopmund District, Erongo Region, Namibia. © Rob Lavinsky, www.iRocks.com. Used with permission.
Scientists have synthesized jeremejevite only in micro-crystalline form and as an OH-end member — with no fluorine (F) present — for research purposes. There is no known jewelry use for this lab-created material.
No known gem treatments or enhancements.
Greenish, faceted jeremejevite, 0.93 cts, Namibia. Photo by DonGuennie. Licensed under CC By-SA 4.0.
First discovered as small, single crystals in loose granitic debris under the turf on Mt. Soktuj, Nerchinsk district East Siberia, Russia, jeremejevites were first found in facetable form in Cape Cross, near Swakopmund, Namibia. These were very long, blue-green pyramidal crystals, up to 2 cm (e = 1.639; o = 1.648; birefringence 0.007).
In 2001, Namibia revealed a new source, about 180 km east of Cape Cross in the Erongo Mountains near Usakos.
Additional sources include the following:
Jeremejevite crystal formed as an acicular ball, diameter 0.04 mm. Wannenköpfe, Ochtendung, Eifel region, Germany. Photo by Fred Kruijen. Licensed under CC By-SA 3.0 NL.
The Swakopmund crystals could yield faceted gems up to about 5 carats. However, typical faceted stone sizes from this material range from under 1 carat up to about 2 carats.
New sources have produced much larger faceted jeremejevites. The 2008 Tucson Gem and Mineral Show featured a 59.58-ct faceted gem from Madagascar. In 2014, The Journal of Gemmology published a study of a faceted jeremejevite weighing 106.50 cts. Reportedly cut from a 254-ct rough found in Sri Lanka in the 1990s, this is the largest known faceted jeremejevite.
Although jeremejevites can make durable jewelry stones, avoid cleaning them in mechanical systems that involve ultrasound or steaming. These gems may contain inclusions, notably liquid inclusions, that could shatter these rare stones if subjected to these methods. Instead, use warm water, mild detergent, and a soft brush.
Consult our gemstone jewelry cleaning guide for more recommendations.
3.20-ct jeremejevite, mined in the Erongo Mountains, Namibia. Photo © Claradyn Venter. Used with permission.
IGS Newsletter
