While comparing Proustite and Labradorite 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 Proustite and Labradorite chemical formula.
Another important criteria for qualitative analysis of gemstones is Proustite and Labradorite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Proustite and Labradorite Optical Properties during the identification of gemstone. Specific gravity of Proustite is 2.69-2.72 whereas that of Labradorite is 2.69-2.72.