Ruby is a jeweler variety of the mineral corundum (chrome-containing variety), colored in a rich red color with light orange or purple hues or without them. The name comes from the Latin "rubeus" for "red".

Chemistry: Al2O3;

Crystal system: Trigonal, ditrigonal-skalenohedral crystal class (point symmetry group);

Color: Red, red with a weak orange hue, red with a weak or strong purple hue.

The color of a ruby is due to the element chromium (Cr3+).

Identification properties

Physical properties
Mohs hardness: 9
Density: 4.00±0.03 g/cm3
Cleavage: none
Fracture: conchoidal
Optical properties
Optical character: anisotropic, uniaxial, negative
Refractive Index: ne = 1.760-1.764, no = 1.768-1.772
Birefringence: 0.008 – 0.009
Pleochroism: from weak to clear in red hues
Dispertion: 0.018 (BG)
Luster: vitreous

Inclusions and structural inhomogeneities

Gem basic treatments

Heat treatment Removing of purple or orange hue, as well as for rutile microinclusions dissolving that enhances the clarity
Heat treatment in a flux mixture Healing of fractures (cracks)
Hydrothermal build-up of the synthetic ruby layer Altering and improving the apparent clarity and color of gem material
Diffusion treatment including the use of beryllium salts Improving a ruby red color
Healing of fractures (cracks) or impregnation with high refractive glasses or colored compositions to fill the open cavities Altering and improving the apparent clarity and color of gem material
Surface coating by applying a various coloring agent Altering the gem visual color

Inclusions and structural inhomogeneities

Heat treatment