Irradiative coloration of quartz and feldspars with application to preparing high-purity mineral separates
Visible discrimination of quartz and feldspars can be greatly facilitated by the irradiative coloration of mineral concentrates using γ-radiation from a ^(137)Cs source. Irradiated quartz samples typically become smoky colored. Sanidine phenocrysts generally acquire a yellow color while plagioclase and plutonic K-feldspars respond weakly or negligibly to irradiation. Manual separation of 0.25–3.0-mm mineral grains that were initially identical in appearance was readily accomplished following radiation treatment. Available data indicate that this process does not modify the chemical or isotopic composition of the sample.
© 1994 Elsevier Science B.V. Received June 2, 1993; revision accepted November 3, 1993. We thank A.M. Hofmeister for valuable discussion. This research was supported in part by NSF grants EAR-9204981 (R.E.C.) and EAR-891604 (G.R.R.) and by grants from the Geological Society of America and Sigma Xi (T.P.R.).