Corundum ruby

Category: Oxide mineral – Hematite group

 

Chemical formula: Aluminium oxide, Al2O3

 

Strunz classification: 04.CB.05

 

Dana classification: 4.3.1.1

 

Crystal symmetry: Trigonal (32/m)

 

Unit cell: a = 4.75 Å, c = 12.982 Å; Z=6

 

Crystal system: Trigonal (Hexagonal Scalenohedral) Symbol (32/m) Space group: R3c

 

Mohs scale hardness; 9 (defining mineral)

 

Specific gravity: 3.95–4.10

 

Optical properties: Uniaxial (–)

 

Refractive index: nω = 1.767–1.772 nε = 1.759–1.763

 

Pleochroism: None

 

Melting point: 2044 °C

 

Done