Sapphire belongs to the corundum gem family and is more abundant than ruby. Blue sapphires are very popular especially the ones that come from Burma and Kashmir. The sapphires from Kashmir have a deep velvet blue color which is sometimes referred to as cornflower blue. Burmese blue sapphires are an intense, bright blue color which has a tint of purple.
Fancy sapphires such as pink and yellow are becoming very popular. The color range for pink sapphires is soft baby pink to hot bluish pink. The pink color should be uniform and shouldn't contain any lavender or brown tones. Yellow sapphires range in color from pale yellow to intense amber. Pure golden yellow sapphires are rare but can be easily produced by heating sapphires to a golden color.
There are some sapphires that can change color in the presence of a light source but these types of sapphires are rare. Blue sapphires may change from blue-violet in the daylight to red or reddish violet under artificial light.
Sapphires also contain inclusions which help to identify its origins. For example, sapphires that originate from Thailand have tiny liquid drops that resemble fingerprints inside of the stone.
Hardness: 9 Mohs
Specific Gravity: 3.95-4.03
Refractive Index: 1.762-1.778
Crystal Form: Trigonal, barrel shaped, double-pointed hexagonal pyramids and tabloid shapes.