The Color of Purple, February's Birthstone Amethyst
It's generally true for almost all colored stones that that best specimens are packed with color, "saturated." However, in grading a colored gemstone there are other factors that are equally important: brilliance and clarity. For amethyst, well, for any colored gemstone, a specimen that is so dark it's difficult to discern the actual color is a very poor quality gem and has little value. Amethyst owes it's color to manganese impurities. Another variety of quartz, citrine, can be heated to turn purple and is then sold as amethyst. Imitation amethyst is almost always uniformly colored while natural amethyst will show some color banding referred to as "zebra stripes." Amethyst gems from Africa tend to be smaller in size, a deep royal purple and have flashes of red. Amethyst gems from South American countries can generally be much larger and have a softer purple with flashes of blue.
Photo: Custom Design Handmade Natural Amethyst Earrings by Lisa Voelker, All Animal Jewelry