Technically, any crystal
of the mineral corundum
which is not red (and therefore is a ruby
) or a certain type of orange
(and therefore is a padparadscha
) is a sapphire. The darker blue sapphires are the most popular, and sapphires which aren't blue are called "fancy
sapphires"; these come in colors such as green, lavender, pink, a silvery gray-blue, and colorless.
Many of the best-quality sapphire gemstones come from India, Sri Lanka, and Southeast Asia, although recently some have been discovered in Tanzania. Asterism is more common in sapphires (known as "star sapphires") than in many other gemstones.