Although Zircon is not a well-known gemstone it is on the list of important gemstones found today. Many people confuse it with the artificial diamond simulant which is called ‘cubic zirconia’, but the two are very different. True zircon gems occur naturally.
White zircon has been one of the most significant diamond substitutes due to its high dispersion and refractive index. For this, it was often marketed under the misleading trade name of ‘matura diamond’.
There is a great range of colors in which zircon occurs. The white or colorless is likely the least valuable or important. Currently, the most popular zircon is blue which usually occurs with green pleochroism and can result in interesting teal-like colors. Zircon is also remarkably dense and exhibits a pronounced level of birefringence which makes it appear fuzzy and display facet-doubling.
There is also the blue zircon variation which is one of the traditional modern birthstones for December. Its prominence has led to the emergence of the discipline of ‘zirconology’ in gemology. Zircon is the oldest mineral on Earth with samples of it found in Australia dating back to 4.4 billion years ago.
Even though it is white in its purest form, zircon can also occur in yellow, orange, red, green, blue, violet, brown and combinations in between. Some scientists have discovered that zircon actually contains trace elements of uranium and thorium, both of them elements with known half-lives. It was discovered that these two elements are what cause such tremendous variations in the physical properties of zircon.
Classified as low, medium and high zircon in reference to the presence of its optical properties, lower zircon has higher traces of radioactive uranium and thorium with higher zircon having the least of those 2 elements.
As the oldest known mineral on earth, zircon was formed 4 billion years ago which makes it even older than the moon. Most of its deposits are alluvial with Sri Lanka being the best known source for the ‘low’ zircon, followed by countries including Brazil, Korea, Madagascar, Mozambique, Nigeria, Tanzania, Thailand and Vietnam.