Amazonite is a member of the microcline feldspar family and is a 6-6.5 on the Mohs scale of hardness. Amazonite is best for pendants and earrings like most feldspars. 

Colorado is famous for it's amazonite deposits and amazonite has been mined since ancient history in place like Mesopotamia and Egypt. Amazonite has been worshipped as a gem for at least 2000 years. 

The color is thought to come from traces of lead within the crystal structure. It's also referred to as amazon stone or amazon jade although it is nothing like jade in composition.