The demand for emeralds has always been great. However, the ubiquitous mining of green stones, which has not ceased since ancient times, cannot meet the needs: there are few transparent crystals of good gem quality among the emeralds mined on all continents of the Earth.
Moreover, even the highest quality emeralds are endowed with a property that is hardly visible to, say, diamonds. The complex of internal violations of the crystal by connoisseurs is called the “emerald forest”. A stone with a beautiful pattern of cracks and inclusions is sometimes valued no less than a defect-free crystal with a thick even colour.
But only sometimes ... Usually, however, masters practice numerous (albeit of the same type) ways of refining emeralds. The goal is one: to make the defects as less visible as possible, to glue the stone along the lines of probable faults.
From time immemorial, to improve the appearance and practical properties of the stone, it was boiled in vegetable or mineral oils. This method is still in favour, only the fashion for oil changes every 50 years.
An important feature of oils is the ability to transform a liquid into a hardening substance of a lakopodny nature. This lacquer is the same glue, which displaces the air from the cracks, dissolves foreign particles, cements the split pieces of the crystal.
True, not every master knows how to achieve the optimal effect. Other pseudo-specialists are satisfied by simple oiling of the stone - and then the oil eventually becomes cloudy, salted, flows out of cracks, especially during the washing and cleaning of jewellery.
That is why in Russia, supplying, by the way, excellent cedar oil (not without success used for refining emerald the last half century), oiling is not used. Yes, boiling in oil is considered an outdated method: it was replaced by the filling of cracks with hardened polymers.
The colourless epoxy resin is less popular with masters of refining emeralds than hot cedar oil because of its thickness and low penetrating power. However, those of the stone-cutters, who managed to get the ingredients of the required quality, are able to process the emerald in such a way that traces of refining cannot be found without the use of highly sensitive optical technology.
Specially designed for modifying emerald crystals, Permasafe epoxy resin is not available for most workshops: its composition is kept secret.
Plasticizer brand "Optikon", triumphantly put into circulation by Latin Americans in the 80s of the last century, showed his deceit years after the successful first experiments. The emeralds improved by an opticon began to change colour in places of the introduction of a plasticizer. It turned out that not the mineral turns yellow, but the polymer itself...
In Brazil, they considered the tool unsuitable and brought it out of use, but in Colombia - on the contrary, they adopted it and began using it widely in the late 90s.
Hematrate is a relatively new plasticizer for refining emeralds. Recently released the second, even more, effective generation of the product. However, hematrate and its derivatives are not available for free sale: what to feed competitors?
Attempts to use rubbery substances to refine the emeralds failed. Palm tires, well-known to specialists, were used from time to time in the last quarter of the twentieth century but were ultimately considered inappropriate for use.
Absolutely impossible - and yet applicable everywhere in India - is the method of oiling emeralds with green vegetable oil. According to users, the ring with such an emerald can leave green marks on the finger for many years.
Not much better is the African method, which involves refining emeralds by boiling in paraffin or by rubbing paraffin into cracks that go outside.
