While comparing Opal and Californite 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 Opal and Californite chemical formula.
Another important criteria for qualitative analysis of gemstones is Opal and Californite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Opal and Californite Optical Properties during the identification of gemstone. Specific gravity of Opal is 3.32-3.47 whereas that of Californite is 3.32-3.47.