When it comes to choosing the best pick among Blue Gemstones gemstones, Sillimanite is known to be a popular choice!Physical properties of Sillimanite include its hardness, gravity, fracture, cleavage, etc. For any gemstone crystal, Sillimanite Optical Properties are responsible for imparting various physical properties to its structure. Knowledge of these properties is equally important to gem-cutters as well as to consumers. Sillimanite cleavage is nothing but the plane across which the crystal splits during cutting. Sillimanite cleavage is perfect,and specific gravity of Sillimanite is 3.20-3.26.
The physical properties of Sillimanite, in fact, are imparted by the chemical composition of its individual molecule. The reactivity or inertness of the crystal is solely governed by its chemical structure. Chemical composition of Sillimanite is represented by Al 2SiO 5Michael OâDonoghue , Gems, Sixth Edition (2006).