| P number: | P527993 |
|---|---|
| Caption: | Photomicrograph of cornstone. Light: XPL. Magnification: x2.5. Middlefield Quarry, 1.5 miles north-west of Muirkirk, Ayrshire, Scotland. |
| Description: | A brownish-grey limestone mottled in light and darker shades and of stony appearance. This specimen is Upper Old Red Sandstone (Devonian) in age. BGS sample number SL 170. British Geological Survey Petrology Collection sample number S 34854. Photomicrograph details: Light: XPL, Magnification: x2.5. The rock is composed of turbid fine-grained carbonate which is recrystallized along a diffuse network of channels to anhedral carbonate of grain size 0.03-0.1 mm. This coarser clear carbonate (calcite) occupies extensive areas free from the turbid type. The latter contains numerous pellet structures which are sometimes uniformly almost opaque, sometimes composed of an opaque rind on a clear granular centre. Elsewhere the pellet structure is absent or forms only part of a more complex structural aggregate. Rarely irregular concentric structure suggests algal origin. It seems as if the carbonate had been originally deposited as a mud, in which perhaps worms worked faecal pellets, and that this had been brecciated and recrystallized. Streaks of opaque limonite are present. Pellet structure; small ovoid bodies, thought to be faecal pellets, form groups in a matrix of granular, recrystallized calcite. The outer coat of the pellet seems to be more resistant to recrystallization than the interior. |
| Date taken: | Sun Jun 25 00:00:00 GMT 1905 |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Landscape |
| Size: | 397.39 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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