Austinite and Sillimanite Physical Properties
Tenacity
Brittle
  
Tough
  
Solubility
Easily soluble in cold dilute HCl
  
Not Available
  
Durability
Not Available
  
Not Available
  
Specific Gravity
4.12
  
3.20-3.26
  
Fracture
Brittle, Uneven, Brittle, Uneven
  
Splintery
  
Cleavage
Good in two directions parallel to the prism faces {110}
  
{010} perfect
  
Mohs Hardness
4-4.5
  
6-7.5
  
Chemical Composition
CaZn(AsO4)(OH)
  
Al 2SiO 5Michael OâDonoghue , Gems, Sixth Edition (2006)
  
Austinite and Sillimanite Chemical Formula
While comparing Austinite and Sillimanite 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 Austinite and Sillimanite chemical formula.
- Chemical formula of Austinite- CaZn(AsO4)(OH)
- Chemical formula of Sillimanite- Al 2SiO 5Michael OâDonoghue , Gems, Sixth Edition (2006)
Austinite and Sillimanite Specific Gravity
Another important criteria for qualitative analysis of gemstones is Austinite and Sillimanite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Austinite and Sillimanite Optical Properties during the identification of gemstone. Specific gravity of Austinite is 3.20-3.26 whereas that of Sillimanite is 3.20-3.26.