Amazonite rough cut on 1 side from Madagascar.

Amazonite, sometimes called Amazon stone, is a green variety of microcline feldspar. The name comes from the Amazon River, from which a certain type of green stones used to be extracted, but it is doubtful whether green feldspar also occurs in the Amazon region. Amazonite is only found in limited quantities. Previously, it was mined almost exclusively near the Russian town of Miass in the Ilmen Mountains in the Southern Urals, where it occurs in granite rocks. More recently, crystals have also been found in Pikes Peak, Colorado, where it occurs in complexes with smoky quartz, orthoclase and albite in rough granite or pegmatite. Several other locations in the United States, including Crystal Peak in the same Colorado, also contain amazonite layers, and amazonite has also been found in pegmatite layers in Madagascar. Because of the bright green color that the mineral can acquire through polishing, amazonite is also sometimes cut into pieces and used as a gemstone, although fractures can easily occur. People have long wondered where the green color of amazonite comes from. Many thought the color was caused by copper, as copper deposits often have blue and green colors. However, recent studies indicate that the blue-green color is the result of small amounts of lead and water in the feldspar (Hoffmeister and Rossman, 1985).