ARMBOTH DYKE (QUARTZ PORPHYRY) - Lake District, Cumbria
« backARMBOTH DYKE (quartz porphyry)
Armboth Fell, Thirlmere, Cumbria
A good specimen of the well known Armboth Dyke. From an old collection.
A dyke is a sheet of formerly molten rock that was forced up through a vertical crack in a pre-existing rock. The Armboth Dyke cuts through rocks of the Borrowdale Volcanic Group. It is best described as a quartz porphyry. Rocks with larger crystals in a fine-grained groundmass are called porphyrys.
The Armboth Dyke is a distinctive rock and glacial erratics from the dyke have been useful in tracing the directions of ice movement.
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Size: 9 x 8 x 5 centimetres
Weight: 443 grams
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