Powellite Value, Price, and Jewelry Information

Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons

Powellite

An overview on Powellite Jewelry and Gems. Covers details and essential information on the physical properties and characteristics of Powellite gemstones.

Powellite Information

Data Value
Name Powellite
Colors Straw yellow, greenish yellow, pale greenish blue, blue, blackish blue, dirty white (grayish) to gray, brown, blackish.
Crystallography Tetragonal; crystals usually pyramidal (faces often striated), also tabular; massive, foliated, pulvurent, ocherous.
Refractive Index 1.967-1.985
Luster Subadamantine to greasy (on fracture surfaces).
Fracture Luster Greasy.
Hardness 3.5-4
Wearability Poor
Fracture Uneven
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 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.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
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 (+).

Optic Sign Uniaxial +

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; Russia; Morocco.

Name: After the American explorer and geologist, John Wesley Powell.