ANDESITE - Cheviot Hills, Northumberland
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Cheviot Hills, Northumberland
Cheviot Hills, Northumberland
The Cheviot volcano was active around 400 million years ago at the time of the closure of the Iapetus Ocean between what is now England and Scotland. As is typical of volcanoes above subduction zones, it produced a lava called andesite, named after the Andes mountains.
Because the lavas cooled rapidly at the surface, they are generally composed of small crystals too small to see with the naked eye, but occasionally, they also contain large crystals of feldspar, amphibole, or pyroxene, which began forming within the magma as it was cooling at depth.
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Size: 8 x 6 x 3.5 centimetres
Weight: 199 grams