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Uploaded on:
11/03/2009 05:34:52
Digital Asset
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158.97 KB
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P number: P521520
Caption: Mineral specimen of onyx agate amygdale. Dunure Railway, Brown Carrick Hills, Ayrshire.
Description: The specimen is an onyx agate amygdale, consisting of chalcedony in the form of parallel-banded onyx and concentrically-banded agate. The different colours of white, greys and pinks represent different layers laid down at different times by percolating fluids. British Geological Survey Petrology Collection sample number E 3296A. The agate has formed from hydrothermal fluids which have percolated through the rock and precipitated in layers in open cavities. The parallel banding in agates has been used as a way-up indicator, assuming that the mineralizing fluids slowly filled up the cavity by precipitating a series of horizontal layers. The concentric-banded agate infill represents precipitation around the walls of the cavity. Agates have been collected, worked and fashioned for many thousands of years. This specimen is from the Lower Old Red Sandstone (Devonian) Maybole Volcanic Series, Dunure Railway, Brown Carrick Hills. The lavas are generally thin, usually 10-15 feet thick and contain vesicles infilled with amygdales of quartz, chalcedony or agate.
Date taken: 01/01/2003
Photographer: Unknown
Copyright statement: NERC
Orientation: Landscape
Size: 158.97 KB; 1000 x 775 pixels; 85 x 66 mm (print at 300 DPI); 265 x 205 mm (screen at 96 DPI);
Average Rating: Not yet rated
Categories: Best of BGS Images/ Rocks and minerals  


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