They are a variety of microcline feldspar.
While the feldspar family, which includes moonstone, labradorite, and sunstone, is the most abundant mineral family in the world, gemstone quality stones are very rare. They often exhibit phenomenons such as iridescence or labradorescence.
These lovely designer cabochons often have a chatoyancy or shimmer to them.
Amazonite's blue/green or teal green color is a result of lead and water in the feldspar.
This semi precious gemstone material came from pegmatite in Russia.
This semiprecious gemstone material is called Amazonite for the Amazon River in Brazil. Though this material is not found in that area and it is assumed it was named for its resemblance to the color of the rain forest.
Amazonite has been around for more than 2000 years, documented by archaeological finds in Egypt and Mesopotamia. An Amazonite cabochon ring was found in King Tut's tomb, It is believed to be the third cabochon stone in the breastplate of Moses.
Amazonite cabochons have a 6 to 6.5 hardness.
Amazonite is said to assist in gaining self knowledge and in defining one's core beliefs and values. It is said to assist one in setting appropriate boundaries. Amazonite is also believed to assist one in overcoming fear of confrontation or judgement.