Rio Tinto announced an investment of US$55M to go underground at its Kennecott Bingham Canyon mine in the USA, while Glencore acquires an additional stake in the Mara copper project in Argentina.

Both sites are polymetallic copper porphyry deposits with gold-silver-molybdenum mineralisation. The open pit at Bingham Canyon is currently slated for exhaustion in 2032, which is prompting the feasibility to move underground. At Mara the feasibility study for an open pit is expected this year with a 28-year life of mine.

Molybdenum concentrate supply is increasingly being sourced as a by-product from copper mining. Molybdenite, the main molybdenum ore mineral, is a common occurrence in porphyry systems and forms the main feed for technical molybdenum oxide (TMO) used in alloying, metal and chemical industries.

With several large-scale copper porphyry deposits starting to be in sight of a mid-2030 open pit reserve exhaustion, the outlook for molybdenum supply will be closely linked to successful underground expansions and greenfield mines.