B371
SiO2
Found in the Irai District, Rio Grande Do Sul, Brazil
Citrine is quartz with a lemon yellow color. In natural citrine this color is produced by iron. But natural citrine is rare, so amethyst quartz is often heated or irradiated to change its purple color. The dark yellow to red brown color of this specimen formed when it was heated to more than 1000 degrees Fahrenheit.
