Prasiolite, green-quartz or vermarine is a green form of quartz. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, but it's seen in Lower Silesia in Poland. The gem has a refractive index of 1.54-1.553. It is usually produced artificially by heat-treating amethyst. The terms green amethyst and greened amethyst are considered misnomers by gemologists.… (More on Prasiolite)