| P number: | P521293 |
|---|---|
| Caption: | Rock specimen of quartz porphyry. Buchan Ness, Peterhead, Aberdeenshire, Scotland. |
| Description: | The sample is a spectacular igneous rock with large distinctive crystals of orange alkali feldspar, within a darker fine-grained groundmass of intergrown quartz and feldspar. The large feldspars are termed phenocrysts, and are equant or tabular in shape. British Geological Survey Petrology Collection sample number EMC1417. Strictly speaking, this rock should be termed a porphyritic microgranite. The phenocrysts are thought to have grown at depth in the Earth's crust whilst the granite was still molten. Because they formed within a liquid magma, their growth was uninhibited often leading to perfectly-formed crystals. The Peterhead Granite, one of the Caledonian post-tectonic granite intrusions is cut by both microgranite dykes and a series of felsite and quartz-feldspar porphyry dykes. The Peterhead granite has been dated at 406 Ma (Devonian in age). |
| Date taken: | Sun Dec 01 00:00:00 GMT 2002 |
| Photographer: | McTaggart, F.I. |
| Associate: | T.S. Bain |
| Copyright statement: | NERC |
| Additional information: | EMC1417 |
| Orientation: | Landscape |
| Size: | 272.96 KB; 1000 x 775 pixels; 85 x 66 mm (print at 300 DPI); 265 x 205 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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