Since the time it was first discovered, Zircon as a gemstone never quite made the cut as other established gems. However, with the advanced cutting techniques and heat treatments making their presence felt in the traditional manufacturing process, Zircon gemstone has steadily risen as a star performer in recent times. It’s often confused as “Artificial diamond”, and rated as a synthetic material. On the first note, it is not a diamond substitute; it is naturally occurring gemstone with a very different crystalline structure and composition.
Hindus in the scriptures have a Heavenly Kalpa Tree, which is said to be glowing in gold due to the Zircon Halo fruits.
What is Zircon: An Introduction
Zircon exhibits high-intensity birefringence, which often gets hazed out due to double facing. It is very dense in its appearance and has a high dispersion factor and refractive index. They are mostly colourless, and reveal flashes of light—called Fire, when exposed to light. Yes, it is just as brilliant and radiant as diamond, leading to confusion since centuries; Zircon gemstone beads contain traces of radioactive substances, especially Uranium, which explains its irradiation. On Mohs scale, it has a hardnes fctor between 6.5 and 7.5, which means that it can be scratched by diamond. That’s one way to check the property of Zircon gemstone in the market.
Thanks to its irradiation properties, Zircon exhibits some degree of pleochroism too.
Sometimes called metamiction, Zircon gemstones undergo gradual destruction due to the presence of radioactive crystals present in its structure. Hard to believe at first, Zircon is actually the oldest known crystalline structure to be ever formed. Samples discovered in some parts of the world are actually older than Moon! During the initial formation from the molten granite, traces of highly radioactive elements condensed with cooling gemstone, resulting in the formation of Zircon. Uranium and Thorium are common radioactive impurities found in them.
Types of Zircon:
Metamictization results in formation of two types of gemstones—
• Low Zircon— High Metamictization, affecting gemstones
• High Zircon—Unaffected gemstones
Low zircons reveal higher degree of pleochroism, produced due to alpha-radiation from the Uranium/Thorium particles. This pleochroism resulting from radioactivity is called “Pleochorism Halo” or Radiohalo”.
Intensity of the radiohalo reveals the property, purity and age of the Zircon gemstone.
Mostly colourless, Zircon with trace impurities exhibit different colours too—blue, green, yellow, violet, brown and orange/red. Blue Zircon is the most adored low Zircon available in the market, which also reveals its greenish tinge, thanks to pleochroism.
Pure green zircon, however is very rare, and hence, very expensive.
Zircon gemstones hardly undergo any artificial heat treatment. Darker coloured gemstones in brown and grey shades are treated mildly to produce colourless and blue varieties. Since this treatment is temporary, it is hardly given much importance.
Zircon is a neo-silicate, which has beryls and garnet in the family. Peridot gemstone, topaz gemstone, Andalusite, quartz and tourmaline are related gemstones sharing similar origin, though not as dramatic as zircon.
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