Amazonite (sometimes called "Amazon stone") is a green variety of microcline feldspar.
The name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area.
Amazonite is a mineral of limited occurrence. Formerly it was obtained almost exclusively from the area of Miass in the Ilmen mountains, 50 miles southwest of Chelyabinsk, Russia, where it occurs in granitic rocks. More recently, high-quality crystals have been obtained from Pike's Peak, Colorado, where it is found associated with smoky quartz, orthoclase, and albite in a coarse granite or pegmatite. Crystal Peak, Teller County, Colorado is a well-known locality for crystals of amazonite. Some other localities in the United States yield amazonite, and it is also found in pegmatite in Madagascar.
Because of its bright green colour when polished, amazonite is sometimes cut and used as a gemstone, although it is easily fractured.
For many years, the source of amazonite's color was a mystery. Naturally, many people assumed the color was due to copper because copper compounds often have blue and green colors. More recent studies suggest that the blue-green color results from small quantities of lead and water in the feldspar. (Hoffmeister and Rossman, 1985.
Amazonite is a gem variety of microcline feldspar and is usually polished as a cabochon. It displays a schiller of light which is caused by inclusions. Schiller is a lustrous reflection from planes in a mineral grain and is similar to what is more commonly known as iridescence. The schiller is caused by a feature of the stone's crystal structure. Orthoclase feldspar and albite are present in close association, arranged in layers. This causes an interference effect of light.
Amazonite is found in the United States, Brazil, Zimbabwe, Russia, Australia, Namibia. Amazonite is usually light green to blue-green, mottled and sometimes contains light striations.
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