Amethyst is one of three purple minerals traditionally used in jewelry.
Amethysts are characterized by zoning (unevenness) of color, weak dichroism, and the presence of inclusions. The most common inclusions are minerals such as magnetite, goethite, hematite and rutile.
When heated to a temperature of about 250 °, amethyst loses its color, gradually turning into yellow or greenish, and becomes colorless.
When heated to 300-400°C, amethyst turns yellow, orange, or brown, making it similar to another variety of quartz, citrine.
Heating amethyst to 470 - 750 °C produces light yellow, red-brown, green or colorless crystals. In this case, the original color of the crystals can be restored using X-ray irradiation.