Using A Gemstone Refractometer

My birthday is next month, and I am going to buy one of these gemstone refractometers. Maybe not the specific one shown, but one no less. I have been wanting one for a few years now. I have a loupe, dichroscope, and chelsea filter already. I also have a microscope but it is not great for gemstones, but it is helpful. I have so many loose stones that I have no idea what they are, and a few that I am sure are quite valuable stones. The video will show you how to use your refractometer, though if I remember correctly he should have closed the top of the machine not left it open.