The discount rate at which a project's NPV would be zero — its implied annual return.
The discount rate at which the net present value of a project equals zero. Higher IRRs indicate better project economics. IRR is used alongside NPV to evaluate mining project attractiveness to investors.
IRR is how a project is judged against the cost of building it. Financiers generally want to see well above 20% on a junior project, because the study assumptions rarely survive contact with construction.
IRR is highly sensitive to the timing of early cash flows, which flatters projects with small starter pits and back-loaded capital. Read it alongside NPV and capex, never alone.
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.