The Prestige Series II Gemstone Tester has automatic and manual modes with advanced testing features. They can identify CZ, diamonds and other stones such as sapphires. The tester includes linear display for increased information, adjustable gain for small stone sizes, compensation for ambient temperature and fast warm up time - only ten seconds! An auto shut-off saves battery power and a unique, new, anti-fade circuit compensates for stone heating. Low battery indicator for accurate readings.