AMYGDALOIDAL BASALT LAVA - Co. Antrim, Northern Ireland

AMYGDALOIDAL BASALT

An interesting rock with a great name!

Browns Bay, Islandmagee, Co. Antrim, Northern Ireland

Basalt is a dark coloured volcanic rock and when it erupts at the surface it is often full of gas bubbles which formed as the pressure was released on eruption. When the lava hardens into rock the bubbles are left as cavities which are known as vesicles. Over time these cavities often become filled with crystals of minerals such as quartz, calcite or other minerals called zeolites.

These crystal-filled cavities are known as amygdales. The name comes from the latin ‘amygdula’, an almond, because the filled bubbles were frequently flattened and looked like almonds. Any rock with similar filled cavities is known as amygdaloidal.