| P number: | P521551 |
|---|---|
| Caption: | Mineral specimen of dressed mica. |
| Description: | The image shows a number of thin sheets of muscovite mica. They are almost transparent and have a slight silvery-grey sheen. Some sheets have orange surface staining due to the presence of secondary iron minerals. British Geological Survey Petrology Mineral Collection sample number 382. Muscovite mica has the ability to split into very thin layers or sheets. It is also relatively transparent, and is a very poor conductor of heat and electricity. These properties give mica a number of commercial uses, and it was of great economic value before the development of the plastics industry. Mica was quarried during the Second World War at Knoydart and a few other minor localities and processed at Pitlochry. After the mica `books? were extracted from the quarry the first process they underwent was rough dressing. This was initially done near the quarry at Knoydart but soon transferred to the Pitlochry depot. It consisted of splitting the books into sheets and the removal by cutting of the flaws, incrustations and striations. The mica would then be passed to the cutters who, using skill and great care would remove the remaining flaws and trim the edges leaving block mica of irregular shape with a curved and indented outline. Further fine splitting to remove stains and spots required great judgement to balance loss in weight with the possibility of improving the quality of the block. |
| Date taken: | Wed Jan 01 00:00:00 GMT 2003 |
| Photographer: | Unknown |
| Copyright statement: | NERC |
| Orientation: | Landscape |
| Size: | 233.03 KB; 1000 x 901 pixels; 85 x 76 mm (print at 300 DPI); 265 x 238 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Rocks and minerals |
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