The natural formation and occurrence of green quartz.

Abstract

Loose amethyst, citrine, and prase (green) quartz crystals that have been freed by weathering of fractured, vesicular basalt-andesite (Jurassic) occur in a talus rubble near the California - Nevada state line NW of Reno, Nevada. It is hypothesized that long-term low-grade radiation caused the coloration of the amethyst, and that subsequent heating of the amethyst by a basalt-andesite lava flow (Oligocene) changed the amethyst to the citrine and green varieties. Some crystals of each colour variety are of gem quality.-R.V.D.