Colored by an interaction of iron and aluminum, amethyst is a variety of macrocrystalline quartz that occurs in transparent pastel roses to deep purples and violets. Like many other gemstones, the quality of amethyst varies according to its source. Amethyst from the Americas can be found in large sizes as opposed to African amethyst (typically mined in Madagascar and Zambia), which is sometimes small but carries a higher saturation in color. Dark, highly saturated amethyst is also found in Australia and Sri Lanka. Bi-color amethyst beautifully melds the regal purple lavenders of amethyst with the ice whites of white quartz in one gem. Bi-color amethyst occurs because of environmental changes during formation.