The recurring cost of running the mine once it is built, usually quoted per tonne or per ounce.
The ongoing costs to operate a mine, including labor, energy, consumables, and maintenance. OpEx is typically expressed per tonne of ore processed or per ounce of metal produced and directly affects mine profitability.
Opex determines whether a mine survives a downturn. High-capex, low-opex projects endure weak prices; the reverse gets shut in.
108 terms have their own page: the definition, why it matters to an investor, where it shows up in practice, and the mistake people make with it.