Amazonite in beautiful smaller flat stones from Madagascar.

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 stones used to be extracted, but it is doubtful whether green feldspar also occurs in the Amazon region. Amazonite is only found to a limited extent. In the past 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 in the US state of Colorado, where it occurs in complexes with smoky quartz, orthoclase and albite in rough granite or pegmatite. Several other locations in the US, including Crystal Peak in the same Colorado, also contain amazonite deposits, and amazonite has also been found in pegmatite deposits in Madagascar. Because of the bright green colour that the mineral can acquire by polishing, amazonite is sometimes cut into pieces and used as a gemstone, although it can easily fracture. The origin of the green colour of amazonite has long been a matter of speculation. Many thought that the colour was caused by copper, since copper deposits often have blue and green colours. However, recent studies indicate that the blue-green colour is the result of small amounts of lead and water in the feldspar (Hoffmeister and Rossman, 1985).