Sapphire is corundum of any color other than red. The word alone means a blue stone; other colors take a color word, such as yellow sapphire.
In more detail
Iron and titanium cause the blue, and only a few hundredths of a percent of them are enough. Sapphire has the same optics, hardness and toughness as ruby. Many sapphires show color zoning, so the orientation of the table matters.
On a grading report
Labs identify it as (natural) corundum, variety sapphire. A sapphire of another color is named by its color, for example pink sapphire. Treatments go under Further information or Comments.
Related terms
- Corundum: Corundum is the mineral species made only of aluminum and oxygen. Its red variety is ruby, and all its other colors are sapphire.
- Ruby: Ruby is the red variety of the mineral corundum. Chromium causes its red color.
- Fancy sapphire: A fancy sapphire is a sapphire of any color other than blue, such as yellow, orange, pink, purple or green.
- Royal blue: Royal blue is a trade name for a sapphire of intense, saturated, even blue. It is not a single agreed standard.
- Color zoning: Color zoning is uneven color in a gem: bands or patches of deeper and paler color.
- Asterism: Asterism is a star of light that glides across the dome of a gem. Light reflects from fine needles, often rutile, that lie in two or three directions.