Oval mixed-cut spurrite, 2.41 cts, 9.6 x 7.4 mm, Okayama, Japan. © The Gem Trader. Used with permission.
An attractive but uncommon mineral, spurrite has seldom been cut as a gemstone. However, it has the hardness and tenacity to be used for cabochons.
| Data | Value |
|---|---|
| Name | Spurrite |
| Formula | Ca5Si2O8CO3 |
| Colors | Colorless, white, yellow, light blue, gray, lavender-gray, purple. |
| Fracture | Uneven to splintery |
| Hardness | 5 |
| Cleavage | Distinct 1 direction |
| Crystallography | Monoclinic. Crystals anhedral; usually massive, granular. |
| Refractive Index | 1.640-1.679 |
| Birefringence | 0.039 |
| Luminescence | See "Identifying Characteristics" below. |
| Luminescence Present | Yes |
| Absorption Spectrum | Not reported |
| Pleochroism | Not reported |
| Optics | a = 1.640; β = 1.674; γ = 1.679. Biaxial (-), 2V= 40°. |
| Optic Sign | Biaxial - |
| Luster | Vitreous |
| Specific Gravity | 3.0 |
| Transparency | Transparent to opaque |
| Luminescence Type | UV-Long, UV-Short |
| Etymology | After the American geologist, Josiah Edward Spurr (1870-1950). |
| Occurrence | A contact mineral in limestones. |
| Inclusions | Black magnetite crystals |
Purplish spurrite and white hillebrandite crystals on matrix, 2.5 x 1 x 0.5 cm, Fuka Mine, Bicchu-cho, Takahashi City, Okayama Prefecture, Japan. Photo courtesy of liveauctioneers.com and Jasper52.
In 1986, polished slabs of spurrite as well as rough material appeared in substantial quantities at a mineral show. This translucent to opaque material from Mexico had medium to dark purple colors. Since then, other sources have been discovered, but the material is still rarely encountered in the gem trade. The pieces lapidaries do work usually become cabs, beads, and decorative items. Faceted spurrites are extremely rare.
Be aware that some older gemological reference materials identify paraspurrite as a polymorph of spurrite. However, in 2010, the International Mineralogical Association (IMA) Commission on New Minerals, Nomenclature, and Classification (CNMNC) discredited paraspurrite as a species. Any materials identified as paraspurrites are spurrites.
When tested in gem labs, spurrites have shown some variation in their fluorescence. Some stones have shown green cathodoluminescence under a beam of electrons as well as green luminescence under shortwave (SW) ultraviolet (UV) light.
Others spurrites have shown different results. In 2004, the GIA tested a specimen that proved inert under SW UV but showed light blue luminescence under longwave (LW) UV. Other specimens examined showed pinkish-orange and orange cathodoluminescence. Since these specimens were aggregate minerals, the researchers speculated that some of the components in the specimens could have affected their cathodoluminescence.
Scientists have synthesized spurrites for research purposes, but there’s no known jewelry use for this lab-made material.
No known treatments.
The best known sources for gem material are the Velardeña mining district, Durango, Mexico and Okayama Prefecture, Japan.
Other notable sources include the following:
Spurrite, Luna County, New Mexico. Photo by David Dyet. Public Domain.
You’re more likely to find a spurrite in a mineral collection, if at all, than a jewelry collection.
With a hardness of 5 and distinct cleavage, any cut spurrites should receive protective settings in rings. Other jewelry use, such as necklaces or brooches, should pose no exceptional risks to these stones. However, resist the temptation to just wipe dust and grit off these gems or decorative objects. Spurrites have a lower hardness than household dust (7), which will scratch them. Wash these pieces with a soft brush, mild detergent, and warm water.
For more recommendations, consult our gemstone jewelry care guide.
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