The HRD cert and sarin seem to correspond with one another. Only difference is that if you add the percentages of the cert, depth calculates to 60.5% instead of 60, but I guss that tolerances are just that. At the end of the day you cant pick a stone with the HCA, but it is a very nice tool to help eliminate some of the poor quality that is out there. overall this one seems good and I finally feel good about this purchase. Now I have to figure out how to ask her
