Polariscope, mains-powered.

Summary Approx. 7 X 6 X 5 inches, and the filter ("platform") 35mm diameter. Large base, easily rotates. Stone-holder attaches to base for easy positioning of stone.  Built-in light. Guarantee: 1 year. Detail This instrument will show you if a gemstone is singly or doubly refractive. For instance, Moissanite is strongly doubly refractive, diamond is singly refractive. This is, therefore, a very cheap (if a little fiddly) method of distinguishing diamond from Moissanite. You cannot, however, use this instead of a diamond tester because Cubic Zirconia , glass and plastics give the same reading as diamond (they are all singly refractive).  Also included is a conoscope to view a gemstone's interference pattern in order to determine its optic character (Uniaxial or biaxial) - but that is for the advanced user.  Is it easy to use? It's a a little fiddly but  not too difficult. At the top and bottom of the tube are two filters (Polaroid discs), revolve the top filter until everything in the tube appears dark and place the stone on the platform in the middle. Now turn the stone so that it revolves through 360°. If it appears to turn light-and-dark then light-and-dark in the 360° turn, it's doubly refractive. However, some stoneD exhibit this effect erratically (anomalous double refraction); some stones exhibit this effect only in certain directions (turn the stone sideways and test again).  So while a polariscope is a more reliable than most electronic testers at distinguishing Moissanite from diamond, care must be taken when observing the results - which is why I say, "a bit fiddly".   NOTE: this item is not supplied with instructions, it is intended for gemmologists or those who are studying gemmology.   Limitations Mains-powered only, it does not take batteries. Light must be able to pass through the stone, not a problem with transparent stones, you'll have to use a torch to shine light through semi-transparent stones, you cannot test opaque stones. This is a standard gem tester used by gemmologists, it does not come with instructions, you are expected to know how to use it (a bit like a bicycle, it does not come with instructions telling you how to ride it).