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)

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