Saturday, October 16, 2004

Asterism

In mineralogy, starlike figure exhibited in light reflected or transmitted by some crystals. The stars shown by star sapphires, some phlogopite mica, rose quartz, and garnet are due to minute oriented crystals (often rutile) included within the mineral; several sets of inclusions are present, and each set produces its own ray. In minerals with hexagonal or pseudohexagonal

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