While comparing Cinnabar and Alexandrite 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 Cinnabar and Alexandrite chemical formula.
Another important criteria for qualitative analysis of gemstones is Cinnabar and Alexandrite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Cinnabar and Alexandrite Optical Properties during the identification of gemstone. Specific gravity of Cinnabar is 3.69-3.81 whereas that of Alexandrite is 3.69-3.81.