“Chambersite,” triangular step cut, 0.37-ct, Louisiana, by DonGuennie. Licensed under CC By-SA 3.0.
Chambersite is an exceedingly rare mineral. Although it has properties suitable for jewelry use, its crystals occur in very small sizes. Few cut specimens of this colorless, brownish, or purple stone exist.
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| Data | Value |
|---|---|
| Name | Chambersite |
| Crystallography | Orthorhombic. Crystals shaped like tetrahedra, up to 1 cm on edge. |
| Refractive Index | 1.732-1.744 |
| Colors | Colorless, brownish, lilac, purple. |
| Luster | Vitreous. |
| Hardness | 7 |
| Fracture | Uneven, subconchoidal |
| Specific Gravity | 3.49 |
| Birefringence | 0.012 |
| Cleavage | None |
| Luminescence | None |
| Luminescence Present | No |
| Transparency | Transparent to opaque. |
| Absorption Spectrum | Not diagnostic |
| Phenomena | Tenebrescence. |
| Formula | Mn3 B7O13CI. |
| Pleochroism | None. |
| Optics | a = 1.732; β = 1.737; γ = 1.744. Biaxial (+), 2V ~83°. |
| Optic Sign | Biaxial + |
| Etymology | Named after the type locality, Barber’s Hill Salt Dome, Mont Belvieu, Chambers County, Texas. |
| Occurrence | Occurs in brines in extraction wells in salt domes. Also, extremely rarely, in granitic pegmatite. (See “Sources” below). |
“Chambersite,” 0.7 x 0.6 x 0.6 cm, Barber’s Hill Salt Dome, Mont Belvieu, Chambers Co., Texas, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.
Chambersite comprises the manganese (Mn)-dominant member of the boracite group of minerals. Other members include the magnesium (Mg)-rich boracite and the iron (Fe)-rich ericaite.
Theses stones were first discovered in brines in a gas storage well at Barber’s Hill Salt Dome in Chambers County, Texas. Recovering these crystals requires skin diving in brine down to depths of as much as 70’.
Chambersites show tenebrescence. Their colors darken when exposed to sunlight.
Orthorhombic chambersite almost always occurs in very tiny, tetrahedral crystals. This typically isometric shape reveals chambersites initially form at a higher temperature as isometric crystals. When they cool, their atoms reorganize into an orthorhombic symmetry.
In fact, due to their triangular pyramid shape, chambersites typically receive triangular cuts when faceted. Faceters bevel and polish off part of the tetrahedron to save the weight of this rare material. Essentially, cut chambersites are truncated crystals with polished surfaces.
Small crystals may be transparent and usually brownish or lilac to purple. Colorless gems also occur. However, faceted pieces are usually not transparent.
When backlit, this gemmy chambersite from the type locality shows its translucency. At 0.8 x 0.8 x 0.8 cm, it’s also unusually large for this species. © Rob Lavinsky, www.iRocks.com. Used with permission.
Colorless chambersites can be distinguished from their colorless boracite brethren by their optical properties and specific gravity. Boracites also luminesce while chambersites don’t.
Although chambersites are quite rare, charoite and sugilite, two purple and opaque to translucent gem materials, have recently gained popularity. Both have some resemblance to chambersite. However, both of these gems have lower hardness and specific gravity values. Chambersites also lack the distinctive swirl patterns of charoites.
Scientists have hydrothermally synthesized chambersite crystals for geological research. Since natural chambersites are multiferroic, synthetics may prove useful for research into electronic or optical devices. However, there is no known use of this material for jewelry.
No known gemstone treatments.
The type locality at Chambers County, Texas and the Venice Salt Dome in Plaquemines Parish, Louisiana produce gem-quality crystals. Nova Scotia and New Brunswick, Canada also produce crystals. In 1971, chambersite as an ore was discovered at the Dongshuichang deposit near Jixian, Tianjin City, China.
In 2002, a study of rhodizite-londonite gems from Madagascar found that a specimen contained inclusions of colorless chambersites. What makes this occurrence so unusual is that it marks the first appearance of chambersites in a granitic pegmatite environment.
The largest crystal in this 15-piece set of chambersites measures 2.3 mm across. Venice Salt dome, Plaquemines Parish, Louisiana, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.
Cut chambersites usually weigh less than 2 carats.
With a hardness of 7, chambersite matches quartz’s resistance to scratching. With a vitreous luster and no cleavage, chambersites would make wonderful and durable jewelry stones. However, you’re more likely to find them in a mineral collection, if at all, than in a jewelry collection. This material requires no special care, except to store it away from sunlight and reserve it for evening wear. For cleaning recommendations, consult our gemstone jewelry cleaning guide.
Chambersite: Texas (0.5). Photo © Joel E. Arem, PhD, FGA. Used with permission.
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