1. July 2016 07:27 /
A rousing gemstone in its purple brilliance, amethyst is one of the key items used in jewellery. Essentially quartz, amethyst gemstones is derived from Greek, which translates to “protected from intoxication”. Its natural colour ranges from light pink to deep overtones of purple, often resembling pigeon’s blood.
In the market, finding a brilliant purple amethyst gemstone from natural deposits is almost impossible. Amethyst gemstones are produced abundantly from the mines of Brazil, to be precise, at Minas Gerais. A place in South Brazil that is revered for its rich paleontological importance, the mines produce largest deposits of the Sobriety Stone.
In order to exaggerate the light shaded amethyst stones produced from mines elsewhere other than Brazil, the gems are treated synthetically. The colour and the properties attained after undergoing the treatments remain irreversible.
Why is Amethyst Purple?
Amethyst is quartz with iron and aluminium impurities impregnated in the structure. Closest siblings to amethyst are Golden citrine and Ametrine.
Here are different amethyst treatments and the effect they have on their commercial value and pricing.
The finest quality of amethyst stones exhibits a strongly reddish purple to light pink with zero zoning on them. Gem dealers prefer to display only amethyst stones with saturated reddish purple with a bright radiance. Natural dark amethyst may look blackish when observed in dim lights.
This is where heat treatment is brought into the picture. Very dark amethyst gemstones are gased in high temperatures to lighten the shade. When done in controlled temperatures, gem manufacturers actually manage to produce light but more saturated shades.
Heating is done at 400 degrees to produce astonishingly stable shades of royal purple. It causes tiny inclusions due to expansion of fractures already existing in the crystal structure. The process imparts a permanent colour that will last forever. All dramatic coloured amethysts have undergone heat treatment at some point of their life.
Sometimes when amethyst gems are not available in the market as per demand, the lapidary takes irradiation as a primary course to produce synthetic amethysts. Commonly, synthetic gemstones are made to resemble amethyst by bombarding Yellow Citrine with Gamma rays. The iron oxide particles in the crystal structure of yellow citrine re-oxidize to give it a natural looking purple shade.
The advantages of using irradiation process to produce marketable amethyst gemstone beads are:
- 100% reversible process, if not subjected to heat treatment
- Cheaper process if done for bulk orders
- A large variety of stones can be used to produce amethyst under lab conditions
Amethyst is seldom subjected to heat treatment. The transformation of amethyst gemstones yield Vermarine or Prasiolite, as it is known more commonly in the market. Natural looking Brazilian amethysts turn to the green-coloured vermarine, at a temperature ranging between 800 to 1350 degrees.
Treated amethyst is cut in rounds and ovals, and hardly in cabochon. Calibrated sizes of amethyst can be shaped in exotic patterns resembling hearts, trillions and shields. Ornamental carvings made of amethyst retain their shade and physical brilliance much longer.
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