All About Rubies

Ruby Technical Information

The main technical characteristics of the ruby are shown below:

Classification:  Mineral
Category:  Mineral
Composition:  Aluminiumchromium oxide
Color/Spectrum:  Red gamma
Atomic (Crystal )Structure:  Hexagonal
Density (Relative):  2.65 - 2.68
Chemical formula:  aluminium oxide with chromium, Al2O3::Cr
Color:   Red, may be brownish or purplish
Crystal habit:  Varies with locality. Terminated tabular hexagonal prisms
Crystal Shape:  Prizmatic
Crystal system:   Hexagonal
Cleavage:  No true cleavage
Fracture:  Uneven or conchoidal
Mohs Scale hardness:  9.0
Molecular formula:  Al2O3
Luster:   Vitreous
Refractive index:  ~1.762-1.770
Pleochroism:  Orangy Red, Purplish Red
Streak:   white
Specific gravity:  4.0
Fusibility:   perfectly
Uses:  Jewelry, ornamental

The major variety is pink sapphire Caused by a color impurity that makes the stone appear pink.