Sapphire is the gem variety of corundum (Al2O3), prized for its brilliance, hardness, and wide range of colors.

Appearance & Color

• Best known for blue hues, ranging from velvety royal blue to light cornflower blue, caused by trace amounts of iron and titanium.

• Can occur in nearly any color except red (red corundum is ruby) — pink, yellow, green, purple, orange (padparadscha sapphire), and colorless.

• Many display excellent transparency and a vivid, saturated tone; some exhibit asterism (a star effect) when cut as cabochons.

Physical Properties

• Hardness: 9 on the Mohs scale — second only to diamond in natural hardness.

• Luster: Vitreous (glassy).

• Cleavage: None (very durable).

• Refractive Index: ~1.762–1.770.

• Specific Gravity: ~3.95–4.03.

Geological Occurrence

• Forms in metamorphic rocks (gneiss, schist) and igneous rocks (basalt, syenite), as well as alluvial deposits.

• Major sources: Sri Lanka, Myanmar, Madagascar, Thailand, Kashmir (famous “cornflower” blue), Australia, Montana (USA).

Special Notes

• Many sapphires are heat-treated to enhance color and clarity; this is widely accepted if disclosed.

• Untreated, vivid sapphires are rare and command high prices.

• Sapphires are symbols of wisdom, loyalty, and nobility, historically used in royal regalia.