A Geoscience Digital Image Library
A Geoscience Digital Image Library
| Title | Thin section of dacite |
|---|---|
| Description | This is a plain polarized thin section of dacite. A markedly porphyritic rock with a uniformly fine-grained holocrystalline matrix. The phenocrysts are chiefly strongly zoned, intermediate plagioclase and a few subrounded, partly resorbed grains of sanidine. The microphenocrysts are brown biotite and green hornblende, the latter showing minor marginal resorbtion rims. The matrix consists chiefly of a very fine-grained quartz-feldspar intergrowth and scattered patches of wispy biotite. |
| Chronostratigraphy | Late Cretaceous |
| Location | USA ▹ Montana. Near Helena. |
| Photographer | Darla Sondrol. 2002-04-09. |
| Collection | Ward’s Collection of Classic North American Rocks #26. |
| Key words | dacite, Montana, thin section |
| Tech details | 1023 KB. Thin section. Nikon FDX-35. |
| GeoDIL number | 2632 |
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