| P number: | P524211 |
|---|---|
| Caption: | Photomicrograph of spherilitic riebeckite felsite. Light: PPL, Magnification x 2. At top of cliffs, 700 foot north-north-east of Bruelligaith, North Roe, Shetland Isles. |
| Description: | The image shows a photomicrograph of a felsitic dyke containing distinctive spherulitic texture. British Geological Survey Petrology Collection sample number S 28515. Light: PPL, Magnification x 2. Light: PPL, Magnification x 2. Spherules in igneous rocks are normally near-spheres and often about the size of a pea, but may vary in size from smaller than a pin-head to larger than a man's fist. In this example the spherules are very small and consist of radially disposed fibrous crystals which because of their small size are not easily identified in thin section. A spherulitic type of non-porphyritic riebeckite-felsite. The riebeckite radiates as needles along radially spherulitic growths of micropegmatite and forms stouter prisms in the granular quartz, micropegmatite and feldspar between the spherulites. The riebeckite-bearing rocks are easily recognized by their blue colour varying in intensity depending on the amount of riebeckite. In the spherulitic type the dark blue spots range in size from 1 mm. to 1 cm. in diameter and are very conspicuous in the pink or whitish matrix. |
| Date taken: | Wed Jan 01 00:00:00 GMT 2003 |
| Photographer: | Hyslop, E.K. |
| Copyright statement: | NERC |
| Orientation: | Landscape |
| Size: | 272.38 KB; 1000 x 667 pixels; 85 x 56 mm (print at 300 DPI); 265 x 176 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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