Amethyst is a type of blue-violet or purple quartz, it is translucent or transparent. The violet color is due to impurities in manganese and iron. Coloration is often unevenly distributed, so sometimes needs a heat treatment in order to be colored uniformly. Prolonged exposure to sunlight or excessive heat gradually makes the color of the stone lighter or becomes yellow, brown or green. Amethyst has been known since ancient Egypt and Anatolia, where it was used as a gemstone and for making jewelry and stamps.