Ruby and sapphire (usually blue, but also in every other color) have been the most important colored gemstones for several thousand years. Originating historically in southeast and central Asia, and more recently in eastern Africa, these colored varieties of the mineral corundum have been much sought as gems because of their rarity, color and durability. Gem corundum can display asterism and chatoyancy due to the presence of oriented mineral inclusions, and in some cases, a change of color when viewed under different light sources.
Ruby and sapphire (usually blue, but also in every other color) have been the most important colored gemstones for several thousand years. Originating historically in southeast and central Asia, and more recently in eastern Africa, these colored varieties of the mineral corundum have been much sought as gems because of their rarity, color and durability. Gem corundum can display asterism and chatoyancy due to the presence of oriented mineral inclusions, and in some cases, a change of color when viewed under different light sources.