The upfront cost of building the mine, before it produces anything.
The upfront costs required to build a mine, including equipment, infrastructure, and construction. CapEx is distinguished from operating costs (OpEx) and is a critical factor in project economics and financing requirements.
Capex is the number that decides whether a junior can realistically develop its own project. A company with a $60M market cap and a $900M capex is not going to build it — it is an acquisition candidate, and should be valued as one.
Compare capex against market capitalisation to see how much dilution or debt financing the project implies. Also watch for capex inflation between study stages, which has been severe across the sector.