JEWELRY TESTING IDENTIFICATION TOOL: This essential tool for gem identification measures the refractive index value of gemstones non-destructively, quickly, and accurately, with a test range of 1.300-3.000 and measurement error as low as ±0.005. PORTABLE AND DURABLES DESIGN: Featuring a scratch-resistant aluminum alloy body, insulated controls, and a clear LCD backlit display, this portable gem tester is lightweight, safe to use, and built for long-term reliability. NON-DESTRUCTIVE AND EASY OPERATION: No refractive oil required—simply bring the sample close to the measuring platform. Includes two calibration blocks for accurate measurement before each use, helping determine if gemstones are uniaxial or biaxial. VERSATILE PROFESSIONAL APPLICATION: Ideals for jewelry appraisal institutions, gem processing factories, quickly identifying single crystal gemstones, twin crystals, diamonds, and various colored gemstones. IMPORTANT USAGE NOTES: Designed for polished gemstone surfaces; cannot measure semi-finished products, gemstones smaller than 2.0mm2, or rough stones, ensuring accurate results when used as intended.