Wulfenite

Wulfenite mineral
Crystal system Tetragonal
Transparency Transparent to Translucent
Luster Resinous to adamantine
Fracture subconchoidal to uneven
Cleavage Distinct
Specific Gravity 6.5 to 7
Hardness 3
Optical Character Uniaxial- Double Refractive
Refractive index 2.28 - 2.40
Birefringence 0.012
Dispersion
Fluorescence
Pleochroism Weak dichroic
Chemical Formula PbMoO4
Comments Soluble in sulphuric acid,
decomposed by nitric acid.
Streak

Wulfenite (WOLF-en-ite) is a lead molybdate, in which calcium may substitute for lead and tungsten for molybdenum; its formula is PbMoO4. It was named for Franz Wulfen (1728 - 1805), an Austrian mineralogist.

Wulfenite ranges in color from orangish-red to orange to yellow and is sometimes color zoned, with a dark "filling" layer between layers of lighter color. Although this mineral is soft and brittle, crystals have been cut into brilliant faceted gemstones.

This is a secondary mineral in oxidized zones of ore deposits containing lead and molybdenum. Sources include Chihauhua, Durango and Sonora, Mexico; Yugoslavia; Czechoslovakia; Austria; Poland; Bohemia; Morocco; the Republic of Zaire; and Australia. Outstanding bright orange-red crystals are found in Yuma County, Arizona; another source in the U. S. is Sierra County, New Mexico.

Wulfenite is brittle and fragile as well as somewhat sensitive to heat. Although cleavages are not troublesome, it must be handled carefully and facets should be inspected often to avoid pitting. Wulfenite should be pre-polished on a smooth tin lap with Linde A and the final polishing done with tin oxide on a wax lap. Recommended crown angles are 33° and pavilion angles, 40°.