The natural radioactivity disrupts the crystal structure and produces the changes in color and density through a process known as metamictization. Sri Lanka is the best known source for green metamict 'low' zircon.Specimens are also found in Burma (Myanmar), and may possibly exist in other well-known zircon deposits in Cambodia.
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.
Blue zircon is one of the traditional modern birthstones for December.
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.
Zircon is also remarkably dense and exhibits a very pronounced level of birefringence.
Zircon has such high birefringence that it may appear fuzzy or display facet-doubling.
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.
However, before the introduction of diamond simulants like cubic zirconia and moissanite, white zircon was actually one of the most popular diamond substitutes, owing to its high dispersion and refractive index, and was often marketed under the misleading trade name of 'Matura diamond'.
The most popular shapes include ovals, rounds, pears, octagons (emeralds) and fancy trillions. These colors aren't necessarily stable, since ultraviolet rays or sunlight can cause color loss or changes.