| P number: | P524268 |
|---|---|
| Caption: | Photomicrograph of slate from Main Ballachulish slate quarry, Argyllshire, Scotland |
| Description: | The image is a thin section of slate from Ballachulish taken under crossed-polarized light. Most of the mineral constituents are so fine-grained that they appear opaque or black in the image. However brightly coloured streaks are present throughout, representing highly deformed and elongate grains, mainly of quartz and muscovite. These define the slaty cleavage. The specimen is of Precambrian, Dalradian age. British Geological Survey Petrology Collection sample number S 35750. This uniform parallel fabric is the slaty cleavage. A slaty cleavage is formed by fine-grained clay minerals and micas aligned on a single set of closely spaced parallel planes of fabric. This governs the splitting properties and thickness of a slate tile. The Main (Ballachulish) Quarry is situated immediately behind East Laroch village. The slates have a dark grey colour and an even surface but show well-marked grain in places; texture medium. Pyrites (`diamonds?) are fairly abundant and of moderate size (1/8 - 3/16 inches) and sometimes concentrated along particular beds. Five seams of especially good quality are known to occur. The quarry, when working had the form of a large opening in the hillside and a deep excavated sink that was usually flooded in the quarry floor. Its major dimensions were roughly 400 yards from north to south and 280 yards from east to west. On the south side, the lip of the quarry was some 300 feet above floor-level, or 420 feet above the bottom of the water-filled sink. |
| Date taken: | Sun Jun 25 00:00:00 GMT 1905 |
| Photographer: | Hyslop, E.K. |
| Copyright statement: | NERC |
| Orientation: | Landscape |
| Size: | 301.18 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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