... , commonly known as Gemstone Refractometer, is the primary and most powerful tool in identify and authenticate polished precious and semi-precious ... refractive index (RI) of a gemstone provides the single most important piece of information to a gemologist seeking to identify ... Case- Refractometer Index Reference List (For 77 common gemstones, i.e. Calcite, Jadeite, Quartz etc.)- User's Manual RHG-181 ...