| P number: | P524302 |
|---|---|
| Caption: | Photomicrograph of peridotite. Light: XPL, Magnification x 2. North-north-west of Hallival, Rum, Invernessshire. |
| Description: | The image is a photomicrograph of peridotite taken under cross-polarized light. It shows opaque specks of chromite and large crystals of olivine showing variable bright birefringence colours. British Geological Survey Petrology Collection sample number S 96998. Light: XPL, Magnification x 2. Light: XPL, Magnification x 2. Chromite is a mineral belonging to the Spinel Group. It is a simple oxide of iron and chromium. Chromium occurs as a trace element in most basic igneous rocks, sometimes in minerals such as chrome-augite or chrome diopside, but more often in accessory chromite. As a basic magma cools, the chromium becomes concentrated at a high temperature and euhedral chromite crystals are precipitated. Because these have a high specific gravity, they tend to settle in the magma body and become concentrated in a basal layer. The Rum ultrabasic complex which includes the peridotites, represents the second stage of development of the Tertiary central intrusion complex. It is shaped like a steep-sided cylinder with a domed roof and consists of sixteen alternating layers of peridotite, gabbro and anorthosite (allivalite). Each band or sheet is composed of peridotite graduating upwards into allivalite, the layering is due to rhythmic accumulation of a crystal precipitate on the floor of a sub-crustal magma chamber. |
| Date taken: | 01/01/2003 |
| Photographer: | Hyslop, E.K. |
| Copyright statement: | NERC |
| X longitude/easting: | 138950 |
| Y latitude/northing: | 796800 |
| Coordinate reference system, ESPG code: | 27700 (OSGB 1936 / British National Grid) |
| Orientation: | Landscape |
| Size: | 283.01 KB; 1001 x 670 pixels; 85 x 57 mm (print at 300 DPI); 265 x 177 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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