Limestone - Purbeck Marble 2
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Fact sheet
Description: 

This sample of building stone is Jurassic limestone from the Purbeck marble quarries near Swanage, Dorset. The building industry calls this type of rock marble and used it as a decorative stone in the construction of churches and cathedrals in southern England. In geology marble implies heating and high pressure but, although it does resemble true marble, this rock has not been metamorphosed.

In thin section the rock is composed of many whole and fragmented gastropod (Viviparus) shells. The shells form a rough alignment, which paralleled the original sea floor surface, and are supported in a fine-grained, calcite-rich mud matrix known as micrite. Some of the larger shells remained whole and were not completely filled by the mud, and in these cases the mud filled only the lower part of the shell, allowing geologists to identify which way was up in the rock. The spaces were later filled by large, clear calcite crystals, known as sparry calcite, which formed from later penetrating fluid

Watson 1911 Building Stones; MO 1316

In Place
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Location description: 
Purbeck marble quarries, near Swanage, Dorset
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Good
Timescale:
Timescale: 
Jurassic
Ma = Millions of years ago
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sedimentary
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