Labels:text | sketch | diagram | circle | font OCR: biotite schist country rock pegmatite tangential biotite defines shell boundaries Large, well developed orbicule about 20cm in diameter with many alternationg shells of biotite and plagioclase. the nucleus is a large black mass of coarse biotite with grains in concentric arrangement. The biotite grains in the shells are tangential to the surface of the spheroidal shells. Near Shoup, Idaho.
