Sold by piece by weight. Sizes may look similar depending on shape/thickness. Each Amazonite stone has been weighted. 
XS: 15g to <20g
SM: 20g to <25g
MD: 25g to <35g
LG: 35g to <45g
XL:  45g to 50g
Stones cranked up by Jay Essex and Diana R. Anaya (Dianimal)
Pictures taken both in natural and artificial lighting