While comparing Blue John and Xonotlite 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 Blue John and Xonotlite chemical formula.
Another important criteria for qualitative analysis of gemstones is Blue John and Xonotlite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Blue John and Xonotlite Optical Properties during the identification of gemstone. Specific gravity of Blue John is 2.71-2.72 whereas that of Xonotlite is 2.71-2.72.