Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
An overview on Prosopite Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of Prosopite gems.
Prosopite Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Prosopite Information
| Data | Value |
| Name | Prosopite |
| Crystallography | Monoclinic; crystals minute, tabular; commonly massive, granular. |
| Colors | Colorless, white, gray. |
| Luster | Vitreous. |
| Hardness | 4.5. |
| Density | 2.88. |
| Birefringence | 0.009. |
| Cleavage | Perfect; not seen on massive material; fracture conchoidal. |
| 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. |
| Spectral | Not diagnostic. |
| Formula | CaAl2(F,OH)8. |
| Pleochroism | None. |
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.
