Molybdenum is contained in various minerals, but only molybdenite (MoS2) is suitable for the industrial production of marketable molybdenum products. Molybdenite can occur as the sole mineralization in an ore body, but is often associated with the sulphide minerals of other metals, notably copper. The Mo content of viable ore bodies ranges between 0.01 and 0.25%.
Depending upon the minerals contained in the ore body and their quality, molybdenum mines are grouped in three classes:
- Primary mines, where the recovery of molybdenite is the sole objective;
- By-product mines, where the recovery of copper-bearing ores is the primary objective, and molybdenite recovery provides additional economic value; and
- Co-product mines, where the commercial viability of the mine requires that both molybdenite and copper-bearing minerals be recovered.
If the ore lies close to the surface, open cast pit technology is employed. Here the overburden is excavated to reveal the ore body for easy extraction. If the ore lies deep underground, the underground block caving technique is employed. Here large blocks of ore are undercut and allowed to collapse under their own weight. The resulting rock is removed to the surface for processing.