PORPHYRY (cut and polished cobble) - Montrose, Scotland
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Cut and polished cobble
Lunan Bay, near Montrose, Scotland
Rocks with large crystals in a fine-grained groundmass are described as having a ‘porphyritic’ texture.
This is a lovely little cut and polished water-worn beach cobble of andesite lava with large feldspar crystals in a dark matrix. These lava flows also contain beautiful agates, for which this part of the coastline is famous.
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Size: 8.5 x 6.5 x 2 centimetres
Weight: 200 grams