Amazonite

Amazonite (sometimes called "Amazon stone") is a green variety of microcline feldspar. more...

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 Miyask in the Ilmen mountains, 50 miles southwest of Chehabinsk, 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. 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.

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 is due to small quantities of lead and water in the feldspar. (Hoffmeister and Rossman, 1985)

See also: List of minerals

Read more at Wikipedia.org