Olivine & Augite in Basalt

This specimen is a piece of basalt containing visible crystals of olivine and augite, two minerals commonly formed from cooling magma. The basalt matrix is dark grey to black and fine-grained, typical of volcanic rocks that cooled quickly at or near the Earth’s surface. Olivine appears as olive-green to yellow-green grains scattered through the rock and represents early crystallisation from magnesium-rich magma. Augite occurs as darker green to black crystalline patches or grains and forms slightly later as the magma continues to cool. Together, these minerals indicate a mafic volcanic origin, meaning the magma was rich in iron and magnesium. This type of assemblage is characteristic of basaltic lava flows and provides a clear example of how different minerals crystallise at different temperatures during volcanic processes.