These cavities are caused as molten rock cools. Minerals captured within these cavities precipitate out of the sludge and gem crystals start to grow. Amethysts chemical composition is SiO 2 . and its color is caused by iron and irradiation. It is some times heated to lighten color and remove a smoky component the color can sometimes manifest. It can be heated to produce citrine and green quartz.
Strong light can cause fading.
It is a reasonably hard gem at 7 Mohs and has good toughness making it suitable for all forms of jewelry. This stone is sensitive to heat which can turn it colorless and may also cause it to fracture. If you held it in your mouth it was said to allow you to call spirits to answer questions about life. When the stone was consecrated, it was believed to help the wearer over come wickedness. Water that an aquamarine was soaked in was used to cure eye ailments, respiratory diseased and the hiccups.