Fiery Orange Mineral (Wulfenite from Mexico) in Gem Hall at Carnegie Museum in Pittsburgh, PA
Wulfenite is a lead molybdate mineral with the formula PbMoO4.
It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore". Wulfenite is not hard enough to be classified as a gemstone.
Wulfenite is named for Franz Xavier von Wulfen (1728-1805), an Austrian mineralogist.
Wulfenite crystalizes in the tetragonal system, often occurring as stubby, pyrimidal or tabular crystals. It also occurs as earthy, granular masses. It shows a white streak and has a hardness of 2.75 - 3.0 on Mohs scale of mineral hardness. It is a dense mineral, with a specific gravity of 6.5-7.0.
Wulfenite is found in many localities, associated with lead ores as a secondary mineral associated with the oxidized zone of lead deposits. It is also a secondary ore of molybdenum, and is sought by collectors.
A noted locality for wulfenite is the Red Cloud Mine in Arizona. Crystals are deep red in color and usually very well formed. The Los Lamentos locality in Mexico produced very thick tabular orange crystals. Samples from Phoenixville, Pennsylvania, while usually not bigger than microcrystals, are desirable because of the unusual location.