Gemological Properties of Corundum
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.
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: = 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)
