Powellite Value, Price, and Jewelry Information


Powellite
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

DataValue
NamePowellite
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).
Fracture Uneven; brittle and fragile.
Hardness 3.5-4.
Specific Gravity 4.23 (varies with tungsten content); Indian material 4.26 (colorless) to 4.28 (brown).
Birefringence 0.011.
Cleavage Indistinct.
Dispersion 0.058.
Stone SizesThe 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.
FormulaCa(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.