Sold by piece by weight. Sizes may look similar depending on shape/thickness. Each Amazonite stone has been weighted. 
XS: 10g to <15g
SM: 15g to <20g
MD: 20g to <25g
LG: 25g to <30g
XL:  30g to 35g
Stones cranked up by Jay Essex and Diana R. Anaya (Dianimal)
Pictures taken both in natural and artificial lighting