Basalts: © D. McGarvie OUGS (2003)

© Craven & Pendle Geological Society

Amygdaloidal Basalt : Iceland

Vesicular Basalt from Iceland

Vesicular Basalt : Iceland

Basalt is one of the most widespread and best known igneous rock types. It is the main constituent of the enormous plateau basalts e.g. Deccan in India Typically basalt is a fine-grained, dark-coloured, dense rock which has a dull, granular appearance. It is also the volcanic equivalent of gabbro and is often porphyritic. Commonly basalt is vesicular, that is, it has holes (vesicles) which were once gas bubbles; later, these holes often fill with mineral matter (amygdales). Basalts which formed by underwater eruptions characteristically develop pillow-like shapes.

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Lake District and Iceland