They are made of spectrolite a type of chatoyant feldspar that has been around for 50 years or more in very large amounts on the rockhound market. Today most is coming out of Madagascar and giant amounts are being put on the market. The beads were likely tumbled which causes the finished pieces to have an already worn look in areas due to the cleavage planes in the stone. Some planes are a bit harder than others and are able to be polished more effectively.