Sample: 79AYb 90
| Sample ID: | 79AYb 90 [1] |
| Station ID: | 79AYb 90 |
| AT Num: | |
| Volcano: | Blue Mtn |
| Possible source: | |
| Eruption: | |
| Collector: | Yount, M. E. |
| Date sampled: | 1979-01-01 |
| Sample type 1: | Lava |
| Color: | Light pinkish-gray |
| Final unit: | |
| Text Description: | Light pinkish-gray (5 YR 8/1), vesicular hornblende plagioclase dacite (S; high-silica andesite G) porphyry. Extrusive, possibly a dome. Major phases are hornblende, plagioclase (An 54*), and glass. Poikilitic, brown to green pleochroic hornblende phenocrysts generally have sharp euhedral grain boundaries and no evidence of resorption. Plagioclase phenocrysts are unaltered, although grain boundaries are rounded and the phenocrysts have lines of inclusions in a thin zone parallel to the grain boundary, suggesting resorption and recrystallization. The plagioclase grains include weakly zoned and strongly oscillatory zoned grains that have an average composition of An 54 or greater. The very fine grained groundmass is primarily glass and devitrified glass and a small proportion of microcrystalline plagioclase and hornblende (?). |
| Sample Location: |