porphyry.JPG (98360 bytes)Porphyry is formed from acid magma within the Earth's crust at intermediate depth, so it has slow to intermediate rate of cooling.There are well-developed large crystals (called phenocrysts) embedded in dark and fine groundmass which give it a mixed-grained texture.

Porphyry is hard and resistant. Resistant porphyry dykes always lead to the development of cliffs and waterfalls.

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