Wulfenite Composition, Crystallization and Structure

Composition. Lead molybdate, PbMoO₄ = Molybdenum tri-oxide 39.3, lead oxide 60.7. Calcium sometimes replaces the lead.

Crystallization. Tetragonal; tri-pyramidal. Crystals usually square tabular in habit with prominent base. Sometimes very thin. Edges of tables beveled with faces of low second order pyramid. More rarely pyramidal in habit. Pyramid of third order in small faces and very rare.

Structure. In crystals; also massive granular, coarse to fine.

Physical Properties. H. = 4.5-5. G. = 6.05 Vitreous to adamantine luster. Color yellow, orange, red, gray, white. White streak. Transparent. To sub translucent.

Test. Easily fusible at 2. Gives a lead globule when fused with sodium carbonate on charcoal. With salt of phosphorus in R. F. Gives green bead; in O. F. Yellowish green when hot to almost colorless when cold. It powdered minerals is moistened with concentrated sulfuric acid and evaporated almost to dryness in a porcelain crucible the residue will show a deep blue color on cooling (molybdenum).

Occurrence. Found in the oxidized portion of lead veins with other ores of that metal, specially vanadinite and pyromorphite. Found in the United States at Phoenixville, Pennsylvania, in a number of places in Utah, Nevada, Arizona and New Mexico.

Use. An ore of molybdenum. Molybedun  is used as a steel-hardening metal. In the form of ammonium molybdate it is used as a chemical reagent, as a fireproofing material and as a disinfectant. Molybdenum used also to color leather and rubber.