Things You'll Need
Instructions
Familiarize yourself with the parts of the gemological refractometer. Before you start using this device, you need to know its parts and their functions. Go over the user's manual before you use the refractometer. Alternatively, there are websites that will give you as much information as you need about the instrument.
Put RI liquid near the hemicylinder. You only need to place a really small drop of the solution -- just enough to cover a small portion of the metal base near the hemicylinder. Take care not to put any liquid on the hemicylinder itself.
Mount the gemstone. Place the gemstone right on top of the RI liquid and slide it onto the cylinder without breaking the seal between the surfaces. You're not supposed to lift the stone when you're mounting it onto the hemicylinder because the RI liquid will not be able to seal all openings where light can pass through.
Position the light source to the back of your gemological refractometer. Once you have the stone in place, take the light source (i.e. a penlight or hand torch) and focus the beam on the back, so that light shines through the viewing lens when you look into it.
View the reading scale through the lens. You want to slightly move your head up and down to see the separation of shadowed and lightened areas. This will help you locate the thin, greenish line which would separate light from the shadow. Note the point where the greenish line rests; this will be the measure for your refractive index.