This article has been reviewed and approved by the following Topic Editor: Sidney Draggan (other articles)

Background

Molybdenum is a metallic, silvery-white element, with an atomic number of 42. Its chemical symbol is Mo. Chemically, it is very stable, but it will react with acids. The physical characteristic that makes molybdenum unique is that it has a very high melting point at 4,730 degrees Fahrenheit. This is 2,000 degrees higher than the melting point of steel. It is 1,000 degrees higher than the melting temperature of most rocks. It has the fifth highest melting point of all of the elements.

Molybdenite (MoS₂, molybdenum sulfide) is the major ore mineral for molybdenum (sometimes called moly for short). It is rarely found as crystals, but is commonly found as what mineralogists describe as foliated masses. This means the mineral forms folia or layers, like the mineral mica. It is metallic gray, has a greasy feel, and is very soft at only 1 on Mohs' hardness scale. Its softness, metallic luster and gray color led scientists to mistakenly believe it was a lead mineral. Geologically, molybdenite forms in high-temperature environments such as in igneous rocks. Some molybdenite forms when igneous bodies contact rock and metamorphose, or change, the rock. This is called contact metamorphism.

Molybdenum is also found in the mineral wulfenite (Pb(MoO₄), lead molybdate). Wulfenite forms colorful, bright orange, red, and yellow crystals. They can be blocky or so thin that they are transparent.

Molybdenum is a needed element in plants and animals. In plants, for example, the presence of molybdenum in certain enzymes allows the plant to absorb nitrogen. Soil that has no molybdenum at all cannot support plant life.

Molybdenum was discovered by the Swedish scientist, Peter Hjelm in 1781, three years after Carl Scheele proposed that a previously unknown element could be found in the mineral molybdenite.

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