Gneiss
| Gneiss (pronounced NICE) is a medium to
coarse-grained, banded, granular metamorphic rock.
Disinct colour bands or streaks are produced by the alternation of layers of light (e.g.
quartz and feldspar) and dark-coloured (e.g. biotite and hornblende) minerals. The layers
do not split readily and when broken are not smooth. Gneiss may form from diorite,
granite, shale, sandstone, schist or other rocks. |
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Granitic gneiss
(quartz, orthoclase, biotite) |
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| Granodiorite gneiss |
Gneiss |
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Last updated May 12, 2005
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