The diamond tester utilizes the feature that diamond has very high thermal conductivity. It can effectively and quickly distinguish natural diamond from all models of diamond simulants and metals, except synthetic Moissanite which has similar thermal conductivity to Diamond. Features: 1.Equipped with ultraviolet light to test fluorescent reaction of stones. 2.Easy calibration with Level Meter Volume to match different sizes of stones. 3.Can distinguish stones as small as 2pt. 4.Can be connected with A/C adaptor for long time indoor use. 5.One year limited manufacturer's warranty.