| P number: | P553004 |
|---|---|
| Caption: | Limestone and dolomite.Old quarry, north bank of Allt Coire nan Dearcaig, 50 yards upstream from junction with Allt Airidh a' Char Ross & Cromarty. |
| Description: | A pale violet limestone with films of yellow-green phlogopite. Composed of irregular fragments of calcite in a matrix of turbid, very finely granular calcite. Contorted phlogopite, chlorite and spongy tremolite, partly replaced by the carbonate matrix, are abundant. The matrix invades the fragmental calcite along 'corrosion' embayments and cracks. The rock has clearly been crushed and there are some short lengths of shear lines. After shearing there seems to have been brecciation and more uniform pressure under which the fine matrix formed a plastic medium which showed no shear effects. The mean refractive index of the tremolite is beta = 1.620. Apatite and limonite are accessory. Limestone with mica, chlorite and tremolite, medium-grained, pseudo-gritty mortar-structure, crushed. S 35267. White dolomite with greenish-yellow films. The rock scarcely effervesces with cold dilute HCl. In thin section it is seen to be composed of fractured carbonate fragments with close and often bent twinning, up to 1 mm across, in a matrix of granular clear carbonate of grain-size 0.02 to 0.1 mm. Plates of phlogopite, usually about 0.4 mm long, are numerous and are often concentrated along undulating laminae. The larger carbonate fragments are sometimes replaced spongily by granular carbonate, the detached pieces remaining in optical continuity. Colourless tourmaline is an accessory and is sometimes enclosed in phlogopite. Quartz and small aggregates of kaolin are accessory. No refractive index of carbonate other than that of dolomite was noted in the powdered rock. Dolomite with phlogopite, fine-grained, pseudo-gritty mortar-structure, foliated. SL0260. Britrocks S35267. Magnification x40. Light XPL. |
| 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: | 391.46 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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