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
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
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.
