Corundum is commonly known by some of varieties name such as ruby (red colour), blue sapphire, yellow sapphire, pink sapphire, green sapphire, star ruby, star sapphire and more. Each varieties separated by their colour but also has the same of physical properties and optical properties. The information of some properties may be including the following.

Ruby - Sapphire - Gemstones
Ruby - Sapphire - Gemstones
Ruby - Sapphire - Gemstones













Gemological Properties of Corundum
Chemical Composition
:
Aluminium Oxide (AI2O3)
     
Csystallography
:
Hexagoanal - rhombohedral
 
 

Physical Properties

 
  Hardness
:
9
  Fracture
:
Conchodal (no cleavage)
  Parting
:
Basel and rhombohedral
  Specific Grarity
:
4.00 (+0.10 / -0.05)
 
 

Optical Properties

 
  Colour
:
Various (Red, Orange, Yellow, Pink, Green, Blue, Purple,
   
Brown, Gray, Black)
  Transparency
:
Transparent to semi-translucent
  Luster
:
Subadamantine to vitreous
  Refractive index
:
Riw = 1.770, Rie = 1.762 (+0.009 / -0.005)
  Birefringence
:
0.008
  Dispersion
:
0.018
  Fluorescences
:
Various
  Absorption Spectrum
:
Various
  Inclusion
:
Silk, Zircon Crystals, Spinel Crystals, Fingerprint
      Inclusions
 
(Additional commonly seen are hematite, mica, garnet, calcite and corundum)