Gneiss/schist
This rock bears white bands of quartz and feldspar, typical of gneiss, but is dominated by darker layers dominated by biotite, typical of schist. It could be argued is one or the other, or both! This sample displays crenelation (folding) of the banded layers, suggesting it experience multiple stages of compression from different directions as it formed.
This sample is from Triassic age? metamorphic basement rock (Julian Schist) found in alluvial gravel deposits at base of Sawtooth Mountains, eastern San Diego County. California. |
| https://gotbooks.miracosta.edu/rocks/metamorphic/5.html |
2/2/2021 |
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