The easiest way to tell the difference between moissanite and diamond is to view the gemstones under magnification. The typical jeweler’s loupe has a magnification of 10X power. For the trained eyed, 10X magnification should be enough to see what is called “doubling” of the facets. What this means is that the facet junction lines (where the facets come together) on moissanite appear to be doubled.
Another way to tell the difference between moissanite and diamond is specific gravity. Moissanite has a specific gravity of 3.2. Diamond’s specific gravity is approximately 3.5. What does that mean? It means that moissanite is basically less dense than diamond. A side by side diameter comparison of a 6.5 mm moissanite and a 6.5 mm diamond would lead you to believe that they should both weigh the same. However, that is not the case. Moissanite will weigh less than diamond, approximately 0.83 carats. A well-cut diamond of the same 6.5 mm diameter will weigh approximately 1.00 carats. Of course, most of us don’t have a scale capable of weighing carats but if you can get one, now you know the difference.