The model of a mineral industry developed by R. Boadway, N. Bruce, K. McKenzie, and J. Mintz (1987) is extended in two directions. First, it is modified to incorporate explicitly nonrenewability of the resource and is shown to collapse to the case examined by Boadway, Bruce, McKenzie, and Mintz when mineral-bearing land is common property explored by an infinitely large number of firms. Second, the model is extended to capture the effect on the marginal effective tax rate for exploration of the differential tax treatment that exists between exploration costs and mineral property costs. The marginal effective tax rate is increased slightly, but not enough to alter the conclusion that the tax system subsidizes exploration.