While comparing Vishnevite and Fayalite physical properties, the important data you should know is its chemical composition. Since chemical formula defines the molecular structure of the crystal, most of the physical properties like color, tenacity, solubility are governed by Vishnevite and Fayalite chemical formula.
Another important criteria for qualitative analysis of gemstones is Vishnevite and Fayalite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Vishnevite and Fayalite Optical Properties during the identification of gemstone. Specific gravity of Vishnevite is 4.392 whereas that of Fayalite is 4.392.