Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
An overview on Powellite Jewelry and Gems. Covers details and essential information on the physical properties and characteristics of Powellite gemstones.
Powellite Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Powellite Information
| Data | Value |
| Name | Powellite |
| Crystallography | Tetragonal; crystals usually pyramidal (faces often striated), also tabular; massive, foliated, pulvurent, ocherous. |
| Colors | Straw yellow, greenish yellow. pale greenish blue, blue, blackish blue, dirty white (grayish) to gray, brown. blackish. |
| Luster | Subadamantine to greasy (on fracture surfaces). |
| Hardness | 3.5-4. |
| Density | 4.23 (varies with tungsten content); Indian material 4.26 (colorless) to 4.28 (brown). |
| Birefringence | 0.011. |
| Cleavage | Indistinct; fracture uneven; brittle and fragile. |
| Dispersion | 0.058. |
| Stone Sizes | The Michigan material is cuttable only to yield extremely minute stones, and until the Indian material was found powellite was essentially unknown as a gem material. The Indian crystals are quite transparent and cuttable, and gems up to about 3 carats have been cut. These are among the rarest of collector gems. |
| Luminescence | Fluoresces yellowish white-golden yellow in both LW and SW. |
| Spectral | Not diagnostic. |
| Formula | Ca(Mo,W)O4. Isostructural with Scheelite. |
| Pleochroism | Blue material is blue/green (Michigan); yellow material is yellow/light yellow (India). |
Optics: o= 1.967-1.974; e = 1.978-1.985.
Uniaxial (+).
Occurrence: A secondary mineral in the oxidation zone of ore deposits.
Houghton County, Michigan: blue cuttable material.
Utah; Nevada; California; Arizona; New Mexico.
Pandulena Hill, Nasik, India: unique occurrence, scattered crystals associated with zeolite minerals in basalt cavities.
Turkey; USSR; Morocco.
Name: After the American explorer and geologist, John Wesley Powell.
 | An Introduction To Turkey’s Gemstones |
