EXPLOSION BRECCIA (LARGE POLISHED SLICE) - St. Austell, Cornwall
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Large polished slice
Evidence of a violent, high pressure shattering of rock
Wheal Remfry, near St Austell, Cornwall
The breccia from Wheal Remfry, in Cornwall is one of Britain's most unusual rocks. It is thought to originate from hot, molten rock under great pressure deep below the surface. A sudden release of that pressure - possibly by the molten rock reaching the surface - led to explosive decompression, causing the adjacent rocks to shatter and the mass of hot fluid and rock fragments to surge upwards, rather like champagne being released from a bottle when the cork is removed. This event occurred about 270 million years ago.
The fragments are granite and other rocks from great depth. As the pressure fell, the black mineral tourmaline crystallised around the rock debris. Breccia is the name given to a rock containing fragments cemented together, but few other breccias have been formed in such a dramatic way.
This is a gorgeous slice, polished on one side.
Presented in a lidded gift box.
Click on a picture for a larger image
Size: 21 x 9 x 2 centimetres
Weight: 727 grams
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