The Presidium Gem Indicator is the industry's one and only handheld digital tester for coloured gemstones, for application in 31 different types of gemstone. With an easy-to-read clear digital LED screen, this smart thermal tester also comes with the Presidium patented refined changeable probe tip, which ensures minimal equipment downtime. The Presidium Gem Indicator probe consists of two linked thermometers; one which is heated electronically, while the other is cooled by the gemstone being tested. The difference in temperature creates an electrical output, which is then amplified and displayed on the new digital organic LED display.