Phenocrysts
Wed, 01/17/2007 - 21:18 — Sarah74656
Unusually large, often euhedral, crystals in an otherwise fine-grained igneous rock. The resultant texture is a porphyritic texture. Phenocrysts are the result of slower crystallisation of the magma than the fin-grained matrix. See Porphyritic texture.
The picture below show such a texture and the large phenocrysts are easy to spot.