Amethyst is the most popular purple gemstone in the world. It is a variety of purple colored quartz and has been used as a personal ornament for over 2000 years. Amethyst is used to produce faceted stones, cabochons, beads, tumble stones and meny other items for jewelry and ornamentation. It is a gemstone durable enough to be used in rings, earrings, pendants, bracelets and other types of jewelry. Huge deposits of amethyst are present in South America and Africa, other deposits of productive amethyst are located in Canada, France, India, Madagascar, Mexico, Morocco, Myanmar, Namibia , Russia, South Africa, Sri Lanka, Tanzania and the United States.
The first step for amethyst to receive its purple color begins during crystal growth, when traces of iron are incorporated into a growing quartz crystal. After crystallization, gamma rays, emitted by radioactive materials present in the host rock, irradiate the iron to produce the purple color. The intensity of the purple color can vary from one part of the crystal to another. These color variations, known as "color zoning", are evident in meny samples of amethyst crystals and often reflect the hexagonal geometry of the crystal. The most intense purple color is often seen near the end of the crystals.
Learn more about amethyst: Wikipedia