| P number: | P552928 |
|---|---|
| Caption: | Hard marly bed, Ballagan Beds. Ballagan Burn, 530 yards north of Ballagan House. Stirling. |
| Description: | Dull grey compact rock, composed of granular and rhomboid carbonate, 0.005 - 0.02 mm grain-size, and accessory angular quartz and muscovite flakes. There is a small amount of interstitial isotropic material. Dolomite, luteous, micrograined, uniform granular. Note on specimens 34968-69-70-72: Refractive index tests on powdered rock always show dolomite as the carbonate. No index for calcite was obtained in any of the rocks, the only variation being slightly on the ankerite side in some grains of S 34972. Since all these rocks effervesce slightly in cold dilute HCl some calcite must be present as a fine dissemination. In powders immersed in oil a thin skin of apparently isotropic material of much lower refractive index is discernible on the dolomite rhombs when these are orientated so that their index is equal to that of the oil. This is the clay cementing material and is only rarely discernible in thin section (34970). When the powdered rock is treated with hot HCl a considerable clay residue is obtained. This does not lend itself to microscopical examination, the only identifiable minerals being quartz chips, and sericite fibres, the main constituent being an aggregate of minute granules in a feebly polarizing base of average refractive index 1.60 - 1.61. SL0195. Britrocks S34972. Magnification x40. Light PPL. |
| Date taken: | Wed Jan 21 00:00:00 GMT 2004 |
| Photographer: | Sutherland, A. |
| Copyright statement: | NERC |
| Additional information: | Description from: Limestones of Scotland: chemical analyses and petrography. Edinburgh : HMSO, 1956. |
| Orientation: | Landscape |
| Size: | 416.70 KB; 1000 x 750 pixels; 85 x 64 mm (print at 300 DPI); 265 x 198 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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