VOLCANIC GLASS   VOLCANIC GLASS
Holyoke Basalt
Hampshire County, Massachusetts

As this basalt from an ancient lava flow cooled and crystallized, it formed a mass of interlocking grains of gray feldspar, yellow and white pyroxene and black iron oxides. The gold and black shape is a pocket of volcanic glass, made from liquid left over after the feldspar and pyroxene crystals formed. Glass (even ordinary window glass) is actually a supercooled liquid, congealed but not yet crystalline. A bright fringe of radiating crystals too small to identify has begun to form around the edges of this glass.

Crossed polarizers

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