Composition - Aluminium oxide ; Hardness - 9
All gem- quality corundum that is not red is called sapphire, yet this name is popularly associated with the colour blue. Variation in colour, due to iron and titanium impurities, spans many shades, but the most valuable is a clear, deep blue. Some stones, called “Colour change sapphire”, exhibit different shades of blue in artificial and natural light.
OCCURRENCE
Good quality sapphire is found in Burma, Sri. Lanka and India. The best Indian Sapphire is cornflower blue, and found in Kashmir, either in pegmatite or as water worm pebbles in alluvial deposits. Sapphire from Thailand, Australia and Nigeria is dark blue and may appear nearly black. Montana (USA) produces sapphire of an attractive metallic blue. Other localities include Cambodia, Brazil, Kenya, Malawi and Colombia.
REMARK
Synthetic sapphire production began in the late 19th century. Commercial quantities became available in the early 20th century.
