| P number: | P524426 |
|---|---|
| Caption: | Photomicrograph of mugearitic lava. Light: XPL, Magnification x 2. South-east slope of Dunsapie Hill, Edinburgh. |
| Description: | The image is a photomicrograph of a thin section of basalt. It is taken under crossed-polarized light in order to highlight the different minerals present. British Geological Survey Petrology Collection sample number ED 283. Light: XPL, Magnification x 2. Light: XPL, Magnification x 2. The birefringence colours produced by mineral types in thin section depends upon a number of factors, but is mainly determined by the crystal structure of the mineral types. For example garnet is classified as a cubic mineral in terms of its lattice structure, and is completely black (isotropic) under crossed polars. Feldspars (which dominate this image) have variable grey birefringence colours. Dunsapie Hill is part of the Arthur's Seat volcanic formation, a 300 feet thick group resting on the Carboniferous Cementstone Group and at the base of the Lower Oil-Shale Group. Dunsapie Hill is an intrusion of massive, columnar jointed olivine basalt and is the type locality for the Dunsapie-type olivine basalt, a macroporphyritic basalt with phenocrysts of labradorite, olivine and augite. To the east of Dunsapie Hill there are lavas including Markle type basalts and mugearites, the latter containing more sodium than usual. |
| Date taken: | Wed Jan 01 00:00:00 GMT 2003 |
| Photographer: | Hyslop, E.K. |
| Copyright statement: | NERC |
| Orientation: | Landscape |
| Size: | 356.62 KB; 1000 x 669 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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