Q: How does Moissanite compare to diamonds? A: Moissanite Diamond Ruby Sapphire Emerald Refractive Index (Brilliance) Dispersion (Fire) Luster Index Mohs Hardness Toughness Specific Gravity 2.65-2.69 0.104 20.4% 17.2% 7.4% 7.4% 4.8% 0.044 0.018 0.018 0.014 2.42 1.77 1.77 1.58 9.25 10 9 9 7.5 Excellent Good* Excellent** Excellent** Good-Poor** 3.21 3.52 4.00 4.00 2.72 The Mohs Scale The Mohs Scale is used to determine the hardness of solids, especially minerals. It is named after the German mineralogist Friedrich Mohs. As indicated in the chart above, moissanite has a Mohs Hardness rating of 9.25. The scale reads as follows, with the hardness and mineral given from softest to hardest: - Source: Kingzett's Chemical Encyclopedia   1 - Talc: easily scratched by the fingernail   2 - Gypsum: just scratched by the fingernail   3 - Calcite: scratches and is scratched by a copper coin   4 - Fluorite: not scratched by a copper coin and does not scratch glass   5 - Apatite: just scratches glass and is easily scratched by a knife   6 - Orthoclase: easily scratches glass and is just scratched by a file   7 - Quartz (Amethyst, Citrine, Tiger's Eye and Aventurine): not scratched by a file   8 - Topaz   9 - Corundum (Sapphires & Rubies) 10 - Diamond: cuts glass * In cleavage direction, otherwise excellent ** Except twinned stones - Source: Charles & Colvard