Zircon is one of the birthstones for December.
It is the oldest mineral on Earth and samples have been found in Australia that are over 4.4 billion years old. It has been treasured as a gemstone for nearly 2000 years.
It is one of the densest gemstones, which means that it will look smaller than other gems of the same weight. As its 50% denser than diamond, when compared with a 1.00ct diamond, a zircon of similar size will weigh about 1.50ct.
Most natural zircons are yellow – brown to orange and red. Rose and rose-orange zircon usually come from Tanzania, and orange to orange-brown zircon from Cambodia. Some brown varieties, mostly found in Southeast Asia, may be heated to produce colourless and blue zircon. These colours aren’t necessarily stable, since ultraviolet rays or sunlight can cause colour loss or changes. Blue is still the most popular zircon colour. Due to pleochroism, blue zircon can look greenish from certain angles. Medium dark, pure blue stones have the most value. Green zircon is very rare and typically very expensive.
Coloured stones are usually brilliant or step cut while colourless stones are most often brilliant cut. Round stones are usually given a standard round brilliant cut, with an extra row of facets at the edges. The most popular shapes include ovals, rounds, pears, octagons and fancy trilliants. Zircon has double refraction so facet junctions can appear doubled from certain angles making it appear fuzzy. This characteristic allows colourless zircon to be distinguished from diamond or cubic zirconia as they are both singly refractive.
In general, zircon is transparent to translucent and has a brilliant, vitreous (glass like) sheen when polished.
Zircon has good hardness and durability (7.5 Moh’s scale ). Heat treated zircon can be brittle and sensitive to knocks and pressure and have the tendency to wear along facet edges so should be limited to protective style settings or occasional wear rings.
Blue zircons can change colour to brown when exposed to ultraviolet radiation in tanning beds or under ultraviolet lamps used to cure acrylic fingernail adhesives. Sometimes the colour can be restored by exposure to low wattage incandescent light.
Avoid the use of harsh cleaning chemicals or agents, especially bleach and acid. You can clean around using a soft toothbrush or cloth and a mild dish washing liquid if needed. Be sure to rinse your stones well using warm water to remove soapy residue.
Always remove zircon jewelry when engaging in any type of physical activity, including household chores, exercise or sports. When storing zircon jewellery, it is best to wrap them individually in a soft cloth or place them separately from one another inside a fabric-lined box to prevent scratches and fractures.