The feasibility of leaching pyrite from coal heaps is analyzed by adapting a model of the heap-leaching process developed in the copper industry. Parameters in the model are first determined through literature review and direct measurement. The model is then used to predict how coal fragments will leach in reaction kettles containing ferric sulfate solution, in columns through which air is circulated, and in actual heaps. Model parameters are verified and refined by kettle and column experiments. The model is then used to determine the optimum heap size and operating procedures. Eight- foot heaps of 1/4-inch coal fragments leach best. The average rate of application of flush solutions should be less than 0.01 Gal/ft2- hr. It should be possible to leach more than 90% of the finely disseminated pyrite from the coal in 9 months, providing the flush solutions are recirculated. Removal of pyrite from coal utilizing such a process is economically attractive. A heap-leaching operation capable of depyritizing 1 million tons of coal per year has a positive net present value at discount rates up to 16% (base case) to 33% (best case).