Sapphire refers to all gem
varieties of Corundum
, excluding the red variety of Corundum which is classified as Ruby
. In the gem trade, it refers specifically to the blue gem variety of Corundum, unless a color is mentioned as a prefix to sapphire (i.e. Green Sapphire). Sapphire with a color other than blue is often called a "fancy" in the gem trade. See the gemstone section on Sapphire
for complete details.