1. Gemstone Refractometer The diamond tester can quickly and accurately identify single and double refractive gemstones. It helps distinguish diamonds, moissanites, and colored gemstones, speeds up the identification of gemstones in packages, and delivers consistent, reliable results every time. 2. ACCURACY This professional gemstone tester specializes in the rapid and precise identification of single and double refractive gemstones, making it an essential tool for gemologists. With a measuring range of 1.30 to 1.81, it provides versatile identification options. 3. Stable Performance The jewelry refractometer features a visible display for easy reading. Equipped with an integrated light source and a clear digital scale display, it can be used effectively in various environments. 4. HOW TO MEASURE: Place a drop of refractive index oil onto the prism surface using a thin glass rod to determine whether a gemstone is singleaxis or biaxial, photopositive, or photonegative.