Metablastic andesite, with large biotite phenocryst (center) in groundmass of plagioclase, chloritized ferromagnesian minerals and calcite; sample B-33.
Dates
Date Taken
1970
Summary
Metablastic andesite, with large biotite phenocryst (center) in groundmass of plagioclase, chloritized ferromagnesian minerals and calcite; sample B-33. Polarized light. Lewis and Clark County, Montana. Ca. 1970. Published in U.S. Geological Survey Journal of research, v. 3, no. 4, Figure 3-B, page 419. July-August 1975.
Summary
Metablastic andesite, with large biotite phenocryst (center) in groundmass of plagioclase, chloritized ferromagnesian minerals and calcite; sample B-33. Polarized light. Lewis and Clark County, Montana. Ca. 1970. Published in U.S. Geological Survey Journal of research, v. 3, no. 4, Figure 3-B, page 419. July-August 1975.
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