Zircon

Zircon is known since the Middle Ages. The oldest known zircon stones are from Western Australia, with an age of 4.4 billion years. The name probably comes from the Persian word "zargun" which means "gold-colored", though zircon comes in a wide range of different colors.
The most popular zircon color is blue. Most blue zircon come in a pastel blue, but some exceptional gems have a bright blue color. Zircon is also available colorless, green, dark red, violet, yellow, brown and orange.
Due to its high refractive index and strong dispersion, zircon has great brilliance and intensive fire. The luster is vitreous to a brilliant sheen. Colorless stones are brilliant cut. They have fraudulently been offered for "matura" diamond.
On the other hand, natural zircon should not be confused with synthetic cubic zirconia, a common diamond look-alike.