Moissanite Testers

Moissanite is manufactured in the United States by Charles & Colvard, Ltd.  It is a potentially beautiful synthetic gemstone that looks like a diamond to the naked eye.  It also conducts heat at the same speed as a diamond, so a diamond tester conducting heat conductivity testing (which is how most diamond testers work) will not distinguish it from a diamond.  A moissanite has a value of 10% to 15% of the value of a diamond of similar weight and clarity.  So if it is a diamond you are intending to buy, you can lose a lot of money by accidentally taking home a moissanite.

You can distinguish diamond from moissanite in many ways.  For example, you can try a scratch test, because moissanite is softer than diamond.  (Diamond hardness is a 10 while moissanite is 9.25.) The problem with the scratch test is that you can ruin some valuable moissanite, and in fact, put scratches in actual diamond.  This is because diamond has different degrees of directional hardness and the hard diamond point will scratch against any diamond facet presenting a slightly softer hardness direction.

Moissanite is doubly refractive.  When a ray of light passes through it, it is slowed, bent, and split in two.  A diamond is not doubly refractive.  You could examine a gemstone under a triplet loupe and look for double refractivity.  If you find that it is doubly refractive, it is not a diamond.  The problem is that every double refractive gem has at least one direction in which the material behaves like a singly refractive gem.

The most convenient way to test for moissanite is to use a moissanite tester.  A moissanite tester puts an electrical current into the gemstone, and then measures how well the stone conducts the electricity as compared to a diamond.  This method is fast, especially if you are testing multiple stones.  Bright light focussed upon a moissanite will serve to accentuate its characteristic electrical conductivity, making it easier to distinguish moissanite from diamond.  Remember. you will first have to distinguish the "alleged" diamond from simulants like cubic zirconia and some sapphire.  For this you use a diamond tester that relies upon the unique heat conductivity properties of diamonds.  Each type of gemstone has its own characteristic rate for conducting heat.  It is best to use a diamond tester that is a multi-tester, i.e., one that applies the heat conductivity test and the electrical conductivity test at the same time, eliminating both simulants and moissanite.