DETERMINAT ION OF CALCITE, DOLOMITE, QUARTZ AND CLAY CONTENT OF CARBONATE ROCKS 1

The need for quantitative analysis of the major mineral constituents in carbonate rocks resulted from studies of carbonate aggregates u ed in highway concrete. Three quantitative X-ray methods for calcite and dolomite are investigated. The first, a compara-tively simple X-ray method, determines the relative percent of the carbonate fraction that is calcite and dolomite by measuring the intensity ratios of the largest diffraction maxima of the respective minerals. The sample preparation and X-ray procedures were changed and the altered method experimentally shown to be reliable. The second, a combination of chemical and X-ray procedures, involves the X-ray determination f the structural formulas of calcite and dolomite and an EDTA titration procedure for determining the proportion of calcium and magnesium ions in the sample. Two sources of error were found: (1) non-carbonate mlnera[s in the sample liberating "extra " calcium and magnesium ions dur-ing the EDTA titration procedure, and (2) incorrect structural formulas of dolomite due to inaccurate X-ray calibration curve. The third method, an internal standard technique, was established and calibration curves with confidence belts constructed. This method gives absolute--not relatlve~ values for not only calcite and dolomite bnt also quartz