A method is described for the determination of fluoride in geologic materials utilizing a sodium carbonate fusion and an ion chromatographic method of analysis. Excellent agreement is observed with published values for geologic standards ranging from 0.01% to 6% fluoride in the sample. Estimates of precision were based upon the repetitive analysis of United States Geological Survey standard GSP-1. Results indicate a relative standard deviation for the method of 5%. Detection limits were estimated to be 8 ppm fluoride in the sample at the 90% confidence level.