December Birthstone – Zircon
Our last December brimstone is Zircon. An underrated gem that’s often confused with synthetic cubic zirconia due to similar names and shared use as diamond substitutes, few people realise that this natural gem is available in a variety of colours.
The name zircon likely comes from the Persian word zargun, meaning “gold-coloured.” Others trace it to the Arabic zarkun, meaning “vermillion.” Given its wide range of colours – spanning red, orange, yellow, green, blue and brown – both origins make sense.
Zircon is the oldest mineral on earth, dating back more than 4.4 billion years. Found in the earth’s crust, it’s common in most sands and sedimentary deposits, as well as metamorphic rocks and crystallised magma.
Due to its chemical makeup, zircon has survived ages of geologic events like erosion and pressure shifts – recording these changes like a time capsule. Zircon contains the radioactive element uranium, which changes the stone’s chemical structure and colour over time, giving us important clues about the formation of our planet.
Colourless zircon, known as Matura Diamond, displays brilliance and flashes of multicoloured “fire” that can rival fine diamond. There’s one key difference though – Zircon is more brittle, measuring 7.5 on the Mohs scale of hardness, its faceted edges can chip.
How to buy a Zircon
Whether you’re buying blue zircon to celebrate a December birthday, or selecting another shade just to own a gorgeous piece of earth’s oldest history, zircon offers many options. A wide range of colours at relatively low cost make zircon a popular gem.
Colour – Some zircons display warm autumnal earth tones such as yellowish and reddish brown. Red and green zircons have market value as collectors’ stones, and cat’s-eye zircons occasionally appear on the market. There are also colourless zircons. In the 1920s, heat treatment became customary practice to enhance the colour of zircon gems for jewellery.
Although collectors clearly love zircon’s variety of colours, consumers seem most enamoured of just one hue: blue. Gem dealers report that at least 80 percent of the zircons they sell are blue. Because they’re in greater demand, blue zircons usually command higher prices than any of the other varieties.
Clarity – Zircons are relatively free of inclusions. But many untreated zircons have a cloudy or smoky appearance that, if extreme, can be a negative factor with buyers. Most faceted zircon is free of inclusions that are visible to the unaided eye. Eye-visible inclusions cause a drop in zircon value. Rarely, zircon might contain long, parallel inclusions that create a cat’s-eye effect when the stone is cut as a cabochon.
Cut – It’s a challenge to cut zircon because the gem is brittle. Cutters usually fashion zircon in the brilliant style to take advantage of its brilliance and fire. Zircon can also be found in step cuts, which have rows of parallel facets, and mixed cuts, which are a combination of brilliant and step-cut facets.
Carat – Because zircon is one of the heaviest gemstones, it appears smaller than other gems of equal carat weight.