Zircon is believed to come from the Persian word zargun. Latest dating and analytical techniques has shown that some of the Zircon are 4.404 billion years old, making it the oldest mineral. Zircon has the distinction of being the mineral that comes closest to resembling a diamond, usually due to its high refraction and fire.
Bright and lustrous Zircon comes in brilliant blue hues; also comes in warm autumnal yellows and reddish browns, as well as red and green hues, it can also seem to have more than one color. This effect is called pleochroism. The color of zircons can sometimes be changed by heat treatment.
Zircon Treatments:-
The brown varieties are heat-treated at temperatures of 1472-1832 degrees F (800-1000 degrees C), producing colorless and blue zircons. These colors do not necessarily remain constant; ultraviolet rays or sunlight can produce changes. - Gemstones of the world, Walter Schumann, 2001, p 108
Significant Gem Localities:-
Zircon is mined in Australia, Southern Africa, Burma (Myanmar), Cambodia, China, Kyrgyzstan, Madagascar, Russia, Sri Lanka, Tanzania, Thailand, Vietnam, Asia, America.
Mohs hardness - 7.5