AN INDUSTRY LEADER The Presidium Gem Tester II is based on the invention of Professor Julian Goldsmid from the University of New South Wales in Australia. It was developed to distinguish between diamonds and its other simulants using the principles of thermal conductivity. The Presidium Gem Tester II with Assisted Thermal Calibration provides a quick and easy way to identify diamonds/moissanites and separates up to 16 common colored gemstones based on their thermal conductivity with its clear and direct analog display. NEW INCLUDED CALIBRATION FEATURE As PGT II works on the thermal conductivity of the gemstone, its measurement will be affected by the testing environment. WIth the improved function of Assisted Thermal Calibration (ATC), the user is now able to easily calibrate the tester according to the testing environment for a reliable and consistent reading.