Amethyst is the name given to the purple variety of quartz. (The so called "green amethyst" is simply a marketing ploy to sell green quartz!). Amethyst occurs in several places in the world, and can vary in colour from pale lavender to the deepest purple. The best quality amethyst is very clear and deep purple with flashes of red. As it is as hard as the quartz which forms a large part of dust, it is fairly resistant to scratching, but diamonds, rubies and sapphires are all much harder, so store your amethyst away from these. Also, UV light can cause amethyst to fade over time, so keep it in the dark when it is not being worn. Very pale amethyst is sometimes heated up in the hope that it will turn yellow to form citrine, the yellow variety of quartz. Most citrine on the market today is produced this way.