| P number: | P528018 |
|---|---|
| Caption: | Photomicrograph of calcareous sandstone. Light: PPL. Magnification: x2.5. Allt na Teangaidh, 500 yards north-east of Balmeanach, Gribun, Mull, Argyllshire, Scotland. |
| Description: | A dark, fine-grained, rough rock, containing many small aggregates of finely divided pyrite. This specimen is Jurassic in age. BGS sample number SL 227. British Geological Survey Petrology Collection sample number S 35085. Photomicrograph details: Light: PPL, Magnification: x2.5. The sample is composed of angular grains of quartz and subordinate, but abundant albite, in a matrix of brownish calcite which tends to form large irregular grains enveloping several grains of quartz. Orthoclase is an accessory constituent, as are muscovite and scarce phosphatic fossil fragments and grains of garnet, zircon and rutile. Thin-walled shell fragments are common. Pyrite and carbonaceous matter are abundant. The former is mostly in small grains and streaks, but locally forms large lumps enclosing many quartz grains. The carbonaceous matter in the rock is black in reflected light, brown in transmitted light and in some larger fragments looks like wood. Dolomite appears in minor amount as rhombs of 0.1 mm size, in the calcite, and may be a very early if not a primary constituent. |
| Date taken: | Sun Jun 25 00:00:00 GMT 1905 |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Landscape |
| Size: | 365.25 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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