| P number: | P527986 |
|---|---|
| Caption: | Photomicrograph of colomite. Light: XPL. Magnification: x2.5. Stream five-sixths of a mile south of Keoldale, Sutherland, Scotland. |
| Description: | A fine-grained, uniform dolomite of grain size about 0.1 mm. This specimen is Cambro-Ordovician in age. BGS sample number SL 175. British Geological Survey Petrology Collection sample number S 34842. Photomicrograph details: Light: XPL, Magnification: x2.5. Local patches of coarser grain with occasional limonitic fillings along the cleavages occur. Stylolitic films of limonitic clay are present but scarce and there are traces of quartz. Dolomite, fine-grained, mosaic. Some is bedded with alternating laminae of 0.01 to 0.05 mm grain size containing numerous streaky impregnations of limonite and occasional laminae of chert and ferruginous material. Small angular grains of quartz are numerous and the rock probably contains some clay. Other parts of the rock are fine-grained, sandy dolomite with some bands of slightly coarser material; composed of grains of dolomite, about 0.03 mm average grain, with subordinate quartz and alkali-feldspar in angular grains up to 0.1 mm long, and some muscovite in small thin flakes. The rock is cut by thin veins of coarser dolomite. There is a local cement of limonite which is only enough to form coatings to the dolomite grains. Limonite is present also along lines of fracture. Chert occurs in sporadic vacuoles. |
| Date taken: | Sun Jun 25 00:00:00 GMT 1905 |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Landscape |
| Size: | 345.38 KB; 1000 x 663 pixels; 85 x 56 mm (print at 300 DPI); 265 x 175 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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