What is Sapphires?
Sapphires are gem varieties of corundum, best known for blue colour but also found in a wide range of natural hues and prized for durability and provenance.
Mineralogy and crystal structure
Reference formula: Al2O3. Sapphire is corundum coloured by trace elements; blue is commonly linked to iron and titanium, while other colours have different causes. The structure shown is a labelled representative corundum model, not a separate sapphire species. Sapphires is classified with oxides and has a trigonal crystal system. Typical hardness is 9–9 on the Mohs scale and specific gravity is approximately 3.9–4.1.
Colour, lustre and habit
Typical colours include blue, cornflower blue, pink, yellow, green, colourless. The usual hexagonal, tabular, granular habit and vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Sapphires forms in or is associated with metamorphic rocks, basalt-related deposits and alluvial gem gravels. Important documented localities include Sri Lanka, Kashmir, Myanmar, Madagascar, Australia, Thailand and Montana in the United States.
The durable corundum gem family
Sapphire sells across jewellery and collector markets because one corundum framework can host many colours. Colour, clarity, treatment, cut and origin all affect value, so the scientific variety name should stay connected to the parent mineral.
Collecting and care
Protect from sharp impact and sudden thermal change. Warm soapy water is generally safe; valuable stones should retain treatment and laboratory information.
