Gemstone identification tool: This instrument features a high-sensitivity sensor and LCD screen for non-destructive, and accurate measurement of gemstone refractive index, with a range of 1.300-3.000, accuracy up to 0.001, and error of ±0.005. Clear visual reading: Equipped with a large backlit LCD screen and intelligent electronics, it ensures clear readings in low-light conditions, with each charge supporting up to 10,000 measurements for versatile use in labs, field work, and stores. Testing method: This portable refractometer requires no refractive oil; simply place the sample near the measuring platform to determine if the gemstone is uniaxial or biaxial, and includes calibration blocks for pre-measurement accuracy. Optical measurement principle: Utilizing total internal reflection, it determines the critical refractive index of gemstones for accurate identification, lightweight design and durables aluminum alloy casing for extended lifespan. Compatible with multiple gemstones: Capable of quickly identifying single-crystal and twinned gemstones, natural or synthetic materials, and other solids, specifically designed for measuring refractive index.