Wulfenite: Facts & Infromation

Wulfenite is a rare mineral belonging to the class of minerals called molybdates and if found in large amounts it can be used for the extraction of molybdenum.

The wulfenite occurs always in clear crystals, their shapes being closely related to the acidity and oxidative character of the crystallization environment : most often in thin square tablets, and more rarely in elongated tetragonal octahedra, it is also rarely found in prisms or pseudo-cubes.

Wulfenite was first described in 1845 for an occurrence in Bad Bleiberg, Carinthia, Austria. It was named for Franz Xavier von Wulfen (1728–1805), an Austrian mineralogist.

Wulfenite with mimetite, Rowley Mine, Maricopa County, AZ.
Wulfenite from Ojuela mine, Mapimi, Durango, Mexico
Photo on the left: Allans_minerals/IG
Photo on the right: Exotic Crystals

Wulfenite has the composition PbMoO4, and so belongs to an unusual class of minerals called “molybdates.” Minerals are divided into classes based on the composition of their anion group.

Wulfenite is found in the oxidation zone of lead deposits. Oxidation zones are home to some of the world’s strangest and most diverse minerals, as the influence of water and free oxygen interacting with the primary ore body create new and unique minerals.

Other minerals associated with wulfenite in the lead ore oxidation zones are: pyromorphite, a bright green, barrel-shaped lead phosphate mineral; vanadinite, a deep crimson, lead vanadate mineral; and mimetite, an often bright yellow, lead arsenate mineral. Combinations of these lead oxidation minerals create other-worldly color combinations, prized by collectors.

Molybdenum’s high melting temperature makes it a useful industrial metal. It is important in oil refinery and when alloyed with iron, increases the strength of steel. Although most molybdenum comes from the appropriately named mineral, molybdenite, wulfenite deposits can also be used as a minor ore of the metal.

Platy Crystals of Wulfenite Across the Top of This Matrix With Orange Mimetite From San Francisco Mine, Sonora, Mexico.
Credit: Weinrich Minerals, Inc

Properties:

Crystal System: Tetragonal
Chemical Formula: PbMoO₄
Crystal habit: Thin tabular to pyramidal
Colour: Orange-yellow, yellow, honey-yellow, reddish-orange, rarely colourless, grey, brown, olive-green and even black.
Streak: White
Hardness: 2½ - 3
Association: Cerussite, anglesite, smithsonite, hemimorphite, vanadinite, pyromorphite, mimetite, descloizite, plattnerite, Fe–Mn oxides.
Name: To honor Franz Xavier Wulfen (1728–1805), Austrian–German Jesuit, who wrote a monograph on the lead ores of Bleiberg, Austria.
Type Locality: Mining Academy, Freiberg, Germany.
Occurrence: A secondary mineral formed in the oxidized zone of hydrothermal lead deposits, the molybdenum commonly introduced externally.