Analytical methods used in geochemical prospecting for copper were compared by analysis of samples of residual soil collected in duplicate near a copper-bearing vein at the Malachite mine, Jefferson County, Colo. In this area barren or "background" samples have a mean copper content of 58 ppm (parts per million) and anomalous samples containing copper derived from the vein have a mean copper content of 216 ppm. Most anomalous samples are above 100 ppm and most barren samples are below. Geochemical prospecting tests, such as the spectrographic, biquinoline, dithizone and chromograph tests for copper and the citrate soluble and acid-soluble tests for total heavy metal, are almost as sensitive but are less precise and less accurate than standard quantitative trace analysis. Statistical techniques based chiefly upon the coefficient of variation show that the geochemical prospecting tests differ considerably among themselves in sensitivity, precision, and accuracy. This study indicates that the dithizone and the biquinoline tests for copper are the best for geochemical prospecting in this area.
