While comparing Londonite and Narsarsukite 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 Londonite and Narsarsukite chemical formula.
Another important criteria for qualitative analysis of gemstones is Londonite and Narsarsukite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Londonite and Narsarsukite Optical Properties during the identification of gemstone. Specific gravity of Londonite is 2.72-2.83 whereas that of Narsarsukite is 2.72-2.83.