December Birthstone-Zircon, Tanzanite or Turquoise

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Zircon is the December birthstone.

The name Zircon is derived from the Arabic word "Zar gun" which means "gold like". Golden yellow color is one of the commonest colors in which zircon is found naturally.

Zircon occurs in all the different colors of the rainbow, such as red, orange, yellow, green, blue, violet, and also as brown and colorless. At one time the colorless variety of zircon was the most popular, because it resembled diamond in it's luster and brilliance. But now the most popular variety is the blue zircon, which comes in all the different shades of blue, such as pastel blue, neon blue,
light blue, deep blue, etc. Sometimes the brown zircon can be heated carefully to give a beautiful blue zircon.

Zircon is composed of a mixture of Zirconium Oxide (ZrO2) and Silicon Dioxide (SiO2).The chemical formula of Zircon is ZrSiO4.Zircon forms tetragonal crystals and therefore has two refractive indices, 2.02 and 1.92.The difference between the two refractive indices is 0.10,which is quite high, and therefore zircon shows strong double refraction leading to doubling of back facets when viewed through the table. Zircon also shows high dispersion and this gives rise to a sparkling effect of the faceted gem.

Zircon has a high specific gravity ranging from 4.60 to 4.70.Therefore Zircons are quite heavy. They have a hardness of 7.5 on the Mohs scale. Even though zircons are quite hard they can chip
out at facet junctions. This is due to an in-built defect caused by disruption in the crystal lattice by radioactive decay of some elements in the crystal, forming fission tracks. The chipping at the facet junctions is due to the fission tracks which are the weak spots on the crystal.

The chief sources of zircon are the Asian countries such as Sri Lanka, Burma, Thailand, Cambodia, and also Australia.

The metaphysical properties of zircon include the power of relieving pain, ensuring a peaceful sleep devoid of nightmares, protecting travelers from disease and injury.



Tanzanite is an alternative December birthstone.

The name Tanzanite is derived from the name of the East African country Tanzania, where the gemstone was first discovered in 1967,and it is the only country in the world where this variety of gemstone is found.

Tanzanites usually appear in different shades of blue, such as the deep blue, ultramarine blue, medium blue, and light blue, but the blue color is always associated with a slight hint of purple. In the rough state most of the crystals have a brownish yellow component, but this can be eliminatedby a careful heating process, leaving only the violet blue color.

Tanzanite is a variety of a gemstone called Zoisite, and therefore tanzanite is actually a blue zoisite. It is composed of Calcium Aluminium Silicate with a hardness of 6.5 to 7.0 on the Mohs scale. Therefore tanzanite has a moderate hardness, and needs special care to prevent scratches.

Tanzanites are less expensive than sapphire ,and therefore sometimes purchased as an alternative to blue sapphire.


Turquoise is an alternative December birthstone.

The name Turqoise is derived from the French" pierre turquois" meaning Turkish stone. Turquoise had been known since the time of the ancient Egyptians, as these stones have been found among ancient Egytian artefacts such as jewelery.

Turquoise had also been used by the Persians, and the sky blue turquoise which is popular in Persia is known as Persian turquoise. There is evidence that the Incas of South America had used turquoise.

Turquoise exists in different shades of blue, such as greenish blue, sky blue, and Robin's egg blue.

Turquoise is a hydrated Phosphate of Aluminium and Copper oxide. It has a hardness of 5.0 to 6.0 on the Mohs scale and a specific gravity of 2.60 to 2.80.The stone is therefore soft and brittle, and usually treated with a binding agent like resin to increase it's durability. Turquoise are usually opaque and very rarely translucent.

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Dr Shihaan Larif
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