A model of optimal mineral exploration effort is used to determine sufficient conditions for a resource rent tax to be neutral with respect to exploration effort. Analyses the revenue implications of different rates of resource rent tax. Firms are assumed to use decision making processes which are implicitly Bayesian in determining how much exploratory information to acquire prior to deciding whether or not to extract. Relates the tax rate and expected revenue from a resource rent tax. Takes account of the impact of the tax on mineral exploration, the likelihood of mining and consequent long-run mineral supply.