Kyanite and Hercynite Physical Properties
Tenacity
Brittle
  
Not Available
  
Solubility
Not Available
  
Not Available
  
Durability
Not Available
  
Not Available
  
Specific Gravity
3.53-3.65
  
4.39
  
Fracture
Splintery, Brittle, Metallic
  
ConchoidalGemdat.org, Uneven
  
Cleavage
[100] perfect [010] imperfect with 79° angle between
  
{111} Indistinct, {111} Indistinct, {111} Indistinct
  
Mohs Hardness
4-7
  
7.5-8
  
Chemical Composition
Not Available
  
Fe2+ Al 2O 4Gemdat.org , Management Team (2012)
  
Kyanite and Hercynite Chemical Formula
While comparing Kyanite and Hercynite 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 Kyanite and Hercynite chemical formula.
>- Chemical formula of Hercynite- Fe2+ Al 2O 4Gemdat.org , Management Team (2012)
Kyanite and Hercynite Specific Gravity
Another important criteria for qualitative analysis of gemstones is Kyanite and Hercynite Specific gravity. Specific gravity is the relative density of a gemstone compared with respect to density of water. Gemologists use Kyanite and Hercynite Optical Properties during the identification of gemstone. Specific gravity of Kyanite is 4.39 whereas that of Hercynite is 4.39.