Sapphire

About it

Corundum of any colour except red, with blue from iron and titanium the classic. Sri Lanka, Madagascar, Myanmar, Kashmir, and Montana are known sources, and most sapphires are heat-treated.

Type

Variety

Group

Corundum variety

Formula

Al2O3

Hardness (Mohs)

9

Specific gravity

3.95–4.05

Streak

white

Lustre

adamantine (diamond-like), vitreous (glassy)

Crystal system

Trigonal

Colours

blue, yellow, pink, purple, green, orange, colourless

Transparency

transparent, translucent, opaque

Cleavage and fracture

none; parting common; conchoidal to uneven fracture

Typical values: real specimens vary. For more, see mindat.org.