| P number: | P521271 |
|---|---|
| Caption: | Rock specimen of foliated gneiss. Footpath, east of Glencanisp House, Lochinver, Sutherland, Scotland. |
| Description: | The rock is a banded and foliated gneiss. The banding is particularly prominent and is probably a primary compositional feature, defined by the central band of dark amphibole surrounded by lighter coloured 'speckled' gneiss composed of interlocking crystals of mainly feldspar and biotite. The gneiss also has a secondary fabric, occurring at a shallow angle to the primary banding, and seen as a faint lineation within the dark amphibole-rich band. British Geological Survey Petrology Collection sample number EMC209. Foliation is a term used in structural geology to describe a planar arrangement of the components of a rock, most commonly a parallel alignment of metamorphic minerals such as mica. The presence of a foliation may allow the rock to preferentially split along that direction, such as in slate. The greater part of the Lewisian (Precambrian) rocks in Scotland were formed in the late Archaean and are the oldest rocks in Scotland at c. 2900-2700 Ma. They formed when the earth's crust was relatively hot and mobile and in consequence the rocks were subjected to repeated deformation and high-grade metamorphism. |
| Date taken: | Sun Dec 01 00:00:00 GMT 2002 |
| Photographer: | McTaggart, F.I. |
| Associate: | T.S. Bain |
| Copyright statement: | NERC |
| Additional information: | EMC209 |
| Orientation: | Portrait |
| Size: | 251.86 KB; 775 x 1000 pixels; 66 x 85 mm (print at 300 DPI); 205 x 265 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Geological structures |
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