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GRANITE PORPHYRY (ELVAN) - Cornwall

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Home > MINERALS > MINERALS FROM BRITAIN AND IRELAND FOR COLLECTORS > SOUTH WEST ENGLAND

  

GRANITE PORPHYRY 'ELVAN' DYKE 

270 million years old (Permian period)

Praa Sands, Cornwall
 
A dyke is a sheet of formerly molten rock that was forced up through a vertical crack in a pre-existing rock.

The dyke at Praa Sands consist of a colourful and attractive quartz-feldspar porphyry, also known as 'elvan' - a Cornish mining term. It was intruded as a magma into the surrounding mudstones ('killas') during the Permian period, some 270 million years ago. The large crystals of feldspar can be clearly seen.

The dyke is a protected Site of Special Scientific Interest and the rock exposures should not be hammered. This sample was from a beach cobble and is from an old university collection.
 
Click on a picture for a larger image


Size:  10 x 7.5 x 4.5 centimetres
Weight:  476 grams

PRICE: £15.00
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