This crystal is Amazonite. It is a potassium-rich feldspar. Which gets Its name because it was discovered or perhaps rediscovered by the Amazon River, from which these green stones were formerly obtained.
Although it has been used for over two thousand years, as attested by archaeological finds in Egypt and Mesopotamia. Though it is unknown whether those stones were amazonite as no ancient or medieval authority explicitly mentions it. It was first described as a distinct mineral only in the 18th century.