Image: Porphyritic trachyte

Porphyritic trachyte (12.5 cm x 9 cm). Upper Fine Flower Rd, Coaldale area, New South Wales.

Photographer:

Stuart Humphreys

Rights:

© Australian Museum

Additional information

Trachyte is a volcanic rock composed largely of alkali feldspar. Porphyry is a general term for igneous rocks that contain phenocrysts (larger crystals) in a finer-grained groundmass.

Last Updated: 27 August 2009

Tags igneous rocks, volcanic, volcanoes, mineralogy, geosciences,