While comparing Bastnasite and Tortoiseshell 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 Bastnasite and Tortoiseshell chemical formula.
Another important criteria for qualitative analysis of gemstones is Bastnasite and Tortoiseshell Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Bastnasite and Tortoiseshell Optical Properties during the identification of gemstone. Specific gravity of Bastnasite is 1.25-1.35 whereas that of Tortoiseshell is 1.25-1.35.