The amounts of calcite, dolomite, anhydrite, strontium, lead and zinc in 832 composite samples taken from Keg River Formation cores in the Rainbow Lake B and D pools have been determined by X-ray fluorescence. Regression equations indicate the average strontium content of calcite, dolomite and anhydrite in these rocks to be 75 ppm, 20 ppm, and 4550 ppm respectively. Two types of calcite have been delineated by differing strontium concentrations. Calcite-dolomite distribution patterns, as well as variations in strontium concentration between wells, are probably due to differing reef geometry and relative changes in sea level. Lead and zinc concentrations are not correlatable with host mineralogy.