Description
Amazonite, sometimes also called Amazon stone, is a green variety of microcline feldspar. The name comes from the Amazon River, from which a certain type of green stone was formerly mined, but it is doubtful whether green feldspar also occurs in the Amazon region. Amazonite has limited occurrences. In the past, it was mined almost exclusively near the city 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 in the US state of Colorado, where it is found 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. Due to the bright green color the mineral can acquire through polishing, amazonite is sometimes chopped into pieces and used as a gemstone, although it can easily fracture. For a long time, people wondered where the green color of amazonite comes from. Many thought the color was caused by copper, since 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).
