Measuring Range: 1.30 ? 1.81 RI Minimum Graduation (RI): 0.01 RI Illumination: Internal illumination with momentary switch Size: 30mm x 70mm x 130mm Scale Division: 0.01 nD Weight: 0.4 kg Ranges of Application: Laboratory, Gemology Filter: Polarizing filter Made of durable heavy metal and scratch proof glass This item is commonly known as Gemstone Refractometer, is the primary and most powerful tool in identifying and authenticating polished precious and semiprecious gemstones and also observing the optical properties and the structure of gemstones. This model is just as good as the expensive models used in gemological institutes, it has a built-in light source and with the aid of the Contact liquid (RI Fluid), which creates an optical contact between the glass and the gemstone, you can measure or test the Refractive Index of faceted stones, its transparency or opacity, and its beauty, durability and scarcity. The refractive index (RI) of a gemstone provides the single most important piece of information to a gemologist seeking to identify an unknown stone. Due to its chemical composition and crystallization structure, each gem has a typical refractive index. In fact, you can also use this tool to measure R.I. for many minerals in crystal form as long as the crystals have a flat and polished face. Through these parameters, you can determine whether the gem is a Single Refraction (Isotropic) or Double Refraction (Anisotropic or Birefringence). Brand New. Comes with lens cloth, RI Liquid, Manual, External Monochromatic Light Source and Carry Case. Ships within 1 business day. Additional Details ------------------------------ Package quantity: 1