6mm. These are AA grade, Chinese turquoise matte finish rounds. They are 100% natural in color and stabilized. In order to make turquoise hard enough to use for jewelry making purposes, it must be stabilized. The matte finish is obtained by honing the stone down to a smooth consistant finish. The result is a lighter color than polished stones. Really pretty! This semi precious gemstone is said to be the stone of communication, helping those who have a fear of public speaking. In the same vein, turquoise is considered to be a stone of friendship, strengthening the bond between friends.