December Birthstones
12月 1, 2020

December Birthstones: Turquoise, Zircon, & Tanzanite


Turquoise is one of a few gemstones that may possess a colouration similar to that of a soothing sky blue. Chemically composed of copper aluminium hydrous phosphate, the colour of turquoise ranges from sky blue, to bluish-green and even yellowish-green. The blue body of the turquoise is due to traces of copper, whereas traces of iron are responsible for the green tint.

Turquoise in matrix
Turquoise from China. Photo: The Gem Museum

Being adored since ancient times, history shows us that turquoise was one of Queen Cleopatra’s favourites. It’s no wonder why because not many gemstones embody the colour blue like turquoise. Today, turquoise from Iran has the more favourable colour of a mid-toned blue, while few other countries also produce good quality specimens, with lighter toned blue as of the sky. 

Although many prefer their turquoise to have a uniform colouration throughout the gem, turquoise is occasionally polished together with its matrix. Matrix is referred to as the host rock where the gem is formed, and due to that it’s not always possible to remove. However, if the matrix patterns are distributed evenly across the stone, it can be truly captivating in the form of “spider webs”.

December birthstones: Turquoise
Turquoise from Chile. Photo: The Gem Museum

Now, turquoise serves as one of the three December birthstones and it is thought to bring good fortunes and welfare to the wearer.


Zircon is the oldest mineral ever discovered, dated to almost 4.4 billion years old, nearly as old as the Earth! This gemstone is basically chemically composed of zirconium silicate, and it possesses a relatively good hardness of 7.5 on the Mohs hardness scale. 

Though seldom sold in the jewellery market, people often ended up confusing zircon with cubic zirconia (CZ), which is widely used in cosmetic jewelleries. What makes them so similar and distinct at the same time is that they both share the same chemical of zirconium, extracted from zircon, but zircon is earth-formed natural mineral whereas CZ is laboratory-made.

December birthstones: Zircon
Brown Zircon. Photo: The Gem Museum

Zircon has been used mainly for jewelleries, widely known for its diamond-simulating abilities. A well-cut colourless zircon may look like a diamond, but one simple trick can differentiate them both. Zircon’s strong doubling effect easily exposes itself due to its doubly refractive nature, while diamond does not show doubling as a singly refractive gem.

Apart from being colourless, yellow, green, red, blue, and more typically brown are some other beautiful colours of zircon. Being one of the December birthstones, this highly versatile gem suits anyone with different colour palates. It is thought to bring inspiration and motivation to achieve one’s goals.


Tanzanite, the latest member among the December birthstones back in 2002, was first discovered in Tanzania in 1967. Until now, it is still only found in that one country on Earth. Possessing the blue that rivals sapphire, it gained recognition and popularity when Tiffany & Co named and publicised it as tanzanite due to its exclusive geographic origin.

Tanzanite possesses a unique optical property that it can show 3 different colours when seen from a different view of the gem, that optical property is called pleochroic. Among the colours can be seen in the gem are blue, violet, and brown. Due to such optic spectacle, gem cutters would have to examine and properly orient the stone’s face-up colour according to its most attractive colour. 

December birthstones: Tanzanite
Tanzanite Earrings. Photo: The King’s Bespoke

The most famous gem variety of the zoisite species for its strong and saturated colour. This sort of colouration has definitely compensated for tanzanite’s moderate hardness of 6.5 as many consider tanzanite as a less expensive alternative to blue sapphires. Some believe that this gem stimulates intuition and aids vitality for the owner.

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