Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Prosopite
An overview on Prosopite Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of Prosopite gems.
Prosopite Information
| Data | Value |
|---|---|
| Name | Prosopite |
| Colors | Colorless, white, gray. |
| Crystallography | Monoclinic; crystals minute, tabular; commonly massive, granular. |
| Refractive Index | 1.501-1.510 |
| Luster | Vitreous to dull. |
| Hardness | 4.5 |
| Fracture | Conchoidal |
| Specific Gravity | 2.88 |
| Birefringence | 0.009 |
| Cleavage | Perfect; not seen on massive material |
| Stone Sizes | Prosopite is a nondescript mineral of no gem significance, except for the beautiful blue material from Zacatecas, Mexico. This material is turquoise-blue, with density variable from 2.69-2.85. Distinction from turquoise is chiefly based on the lower refractive index (1.50 vs. 1.62 for turquoise). Mexican prosopite is evenly colored due to approximately 1.4% copper content. It makes an effective and attractive turquoise substitute. |
| Luminescence | None reported. |
| Luminescence Present | No |
| Transparency | Transparent to translucent. |
| Absorption Spectrum | Not diagnostic. |
| Formula |
CaAl2(F,OH)8.
|
| Pleochroism |
None. |
| Optics |
a = 1.501; β = 1.503; γ = 1.510. Biaxial (+). |
| Optic Sign | Biaxial + |
Optics: a = 1.501; β=1.503; γ=1-510
Biaxial (+).
Occurrence: In tin veins, alkalic pegmatites, and as an alteration product of topaz in volcanic rocks.
St. Peters Dome, El Paso County, Colorado: cryolite deposit.
Dugway district, Tooele County, Utah: greenish color due to a trace of copper.
Santa Rosa, Zacatecas, Mexico: associated with azurite; blue material.
Germany; Tasmania.
Name: From a Greek word meaning a mask, in allusion to the deceptive nature of the material when found as pseudomorphs.
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