Powellite Value, Price, and Jewelry Information
An overview on Powellite Jewelry and Gems. Covers details and essential information on the physical properties and characteristics of Powellite gemstones.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|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).|
|Specific Gravity||4.23 (varies with tungsten content); Indian material 4.26 (colorless) to 4.28 (brown).|
|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.|
|Transparency||Transparent to translucent.|
|Absorption Spectrum||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 (+).|
Optics: o= 1.967-1.974; e = 1.978-1.985.
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; Russia; Morocco.
Name: After the American explorer and geologist, John Wesley Powell.