Emeralds - Part 3

The Jewel Affair in its last two posts has worked towards giving its readers comprehensive information about the most preferred gem in the world – Emerald. The last and the final post of Emeralds will give you an insight on how emeralds are treated for improved appearance and color and also how these gems are manufactured in the lab.

Emerald Treatments

The biggest disadvantage of emeralds is its fractured interiors. To some extent this is what makes the emeralds unique but it also adds a negative mark to the visual appeal. Over the period of time many techniques have been evolved to deal with this problem but the most common and popular methods are:

Oiling

Fracture Filling

Oiling: under this procedure usually oil is used to impregnate the fractures. Most commonly cedar oil is used which is extremely thick and colorless. Firstly emeralds are cleansed with an acid solution and emeralds are placed in specialised equipment where emeralds along with cedar oil are subjected to heat and pressure. As a result cedar oil becomes less viscous and with the help of the pressure penetrates into the cracks. After cooling cedar oil thickens again and results in an improved appearance.

Fracture Filling: the biggest disadvantage of oiling is that eventually it starts fading and it needs to be redone. Owing to this drawback of oiling, resins are filled in the cracks. There is a variety of resins available - natural and artificial. The most common synthetic resin used is Opticon. Often resins are mixed with colors for improving the over all appearance, but the trade does not accept it.

GIA classifies emerald treatments in three categories:

Level 1 – all natural emeralds with colorless filling.

Level 2 – defines the severity of the treatment as ‘minor’, ‘moderate’ or severe.

Level 3 – fillers can be identified upon request.

 

FRACTURE FILLED EMERALD

Most of the emeralds in the market today are treated and these treatments are accepted by the gem trade, but disclosure of the treatment is what helps the consumers to buy gems with confidence.

Synthetic Emeralds

A synthetic emerald can be defined as a lab grown emerald which posseses the same physical and optical properties & essentially the same chemical composition as its natural counterpart. There are two main procedures which are used to synthesise emerald:

Flux process

Hydrothermal process

Flux Process: the flux procedure involves dissolving beryllium, aluminium, silicon, chromium and oxygen to a molten flux in crucible. The crystallisation takes place on a beryl seed crystal. Longer the time given to cool down, bigger the size of the crystal.

This procedure was introduced by Carroll Chatham, a young American chemist in the year 1930. He succeeded in his attempts in the year 1935 and his synthetic emeralds hit the market three years later.

The technique has been improvised with time and now there are many more players in the market along with Chatham namely, Kyocera, Gilson, Farben and many others. 

Magnification is the key to separate these stones from the natural ones. Fingerprint inclusions, parallel growth planes which are also called the 'Venetian Blind' effect, nail head spicules and platinum crystals which come from the crucible lining are usually the give away factors.

FINGERPRINT INCLUSION

NAIL HEAD SPICULES

Hydrothermal Process: the synthesis of emeralds is slightly different here as compared to the flux growth. In this method the essential components are dissolved in an acidic solution  under high pressure and temperature in a chamber inside the synthesis equipment. Then the crystallisation takes place on an emerald seed. Hydrothermally synthesised emeralds are of excellent quality but the cost of production is higher than the flux process.

Johann Lechleitner was the fisrt one who attempted to create emeralds with hydrothermal process in the year 1960.

Russia has been the leading producer of synthetic emeralds whether flux grown or hydrothermally grown.

Hydrothermal emeralds under magnification shown the chevron growth, gold platelets and fingerprint inclusions.

 

CHEVRON GROWTH

The Jewel Affair with this article concludes the emerald chapter and hopes that the readers found it useful.

Emeralds have travelled a long way to tell the stories of the past… Stories of royalty, of being transcended from one generation to another, of invasion, of therapeutic values and spirituality. It is truly one of the most spectacular gem and the way it mesmerises one is absolutely incomparable. In short emeralds are absolute stunners!!