Zircon is not a very well-known gemstone, but it is one of the most important gemstones of today. Many people confuse zircon with the artificial diamond simulant, cubic zirconia. Of course, the two are completely different - cubic zirconia (CZ), is a lab-created synthetic material, while zircon is a naturally occurring gemstone with a very different chemical composition.
Zircon is a tremendously important mineral, indeed its prominence led to the emergence of the discipline of 'zirconology' in gemology. It is the oldest mineral on Earth, with samples found in Australia that are over 4.4 billion years old. Scientists discovered that zircon actually contains trace elements of uranium and thorium, both of which are elements with known half-lives. It is the uranium and thorium that cause such tremendous variations in the physical properties of zircon. Zircon is typically classified as low, medium and high zircon, in reference to the presence of optical properties. Low zircon has higher traces of radioactive uranium and thorium, which causes an alteration in physical structure, rendering it near-amorphous, though its physical appearance remains the same as high or medium zircon. Low zircon is typically green to brownish in color. Green zircon is rarely seen in the gem trade and is highly sought after.