Sillimanite and Onyx Physical Properties

Sillimanite and Onyx Chemical Formula

While comparing Sillimanite and Onyx 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 Sillimanite and Onyx chemical formula.

• Chemical formula of Sillimanite- Al 2SiO 5Michael O’Donoghue , Gems, Sixth Edition (2006)
• Chemical formula of Onyx- SiO₂

Sillimanite and Onyx Specific Gravity

Another important criteria for qualitative analysis of gemstones is Sillimanite and Onyx Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Sillimanite and Onyx Optical Properties during the identification of gemstone. Specific gravity of Sillimanite is 2.55-2.70 whereas that of Onyx is 2.55-2.70.