Ruby

Ruby is the red variety of the mineral called Corundum which is composed of aluminium oxide (any other color of corundrum is a sapphire, see below). The red color is caused mainly by chromium and titanium. It is natural for rubies to have imperfections in them, including color impurities and inclusions of rutile needles known as "silk". Origin of name comes from ruber, Latin for red. Some rubies show a 3-point or 6-point star or asterism. These rubies are cut into cabochons to display this effect. Natural occurring rubies are very rare and extremely rare in large sizes over 3 carats. They can be found in many regions around the world from India, to East Africa, to South America, the Hindu Kush and a few deposits in the United States.