Devitrification of Obsidian
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Devitrification of Obsidian

by Joel Gill, King's College London/Geology for Global Development, London, United Kingdom

A photomicroscope image of devitrifying obsidian, showing a clear nucleus for spherulite growth and their radial growth from this nucleus. Photo taken from a sample of obsidian collected in Northern Chile (2007). In reflecting on the theme 'active planet', this image demonstrates activity at both a large scale (i.e., initial eruption of magma and formation of obsidian) and a small scale (i.e., devitrification of the obsidian).