Photomicrograph showing secondary large round andesine grains in a fie-grained (sic) biotite schist along the North Fork of the Clearwater River near Dent. Clearwater County, Idaho. circa 1950.

Album caption: Photomicrograph showing secondary large round andesine grains in a fie-grained (sic) biotite schist along the North Fork of the Clearwater River near Dent. Large round plagioclase grains shown in top part of photomicrogrpah have crystalized late and disturbed the original foliated structure of the schist. a-andesine, b-biotite, q-quartz. Crossed nicols. Clearwater County, Idaho. c. 1950. Published as figure 80B in U.S. Geological Survey. Professional paper 344-A. 1962.