The Gemmological Association of
Australia outlines some of the treatments used to enhance the appearance of emeralds, aquamarines and other beryls.
Allegations of an undisclosed emerald treatment were at the centre of a US court case that was settled ten years ago, but could just as easily occur today.
The court ruled that the eweller had sold a 3.65 carat emerald without fully disclosing treatment and awarded the cost of the stone, US$14,500, plus triple damages or US$58,000 in total. Add the legal costs and this was one big headache for improper disclosure.
The condition under which emerald forms has resulted in many, if not most, stones having a multitude of very small surface reaching fractures or openings. The practice of filling an emerald with a viscous substance to mask the appearance of these fractures and make the stone appear more transparent goes back many hundreds of years and a number of these treatments are perfectly acceptable worldwide in the jewellery industry.
The first and most widespread of the acceptable treatments is the use of Cedar wood oil or Canada Balsam. Using a specialised machine to clean and prepare the stone, the oil is introduced into the stone using heat and pressure for several hours. Although the use of colourless Cedar wood oil is acceptable it has to be declared and not just for the sake of being honest; exposure to detergents (in the shower, doing the washing up) or ultrasonic will degrade the oil and can lead to a nasty surprise for a client who may find themselves in the possession of a suddenly very included emerald! Jewellers dealing with emeralds in Australia should assume that all stones are at least oiled.
In the case of the US jeweller, however, the treatment used was an epoxy resin called Opticon. This treatment has been around since the 1960s but perhaps not really widely used until the 1980s/1990s. It consists of two parts: a resin and a hardener. The resin is used to fill the emerald and, on occasion, a hardener is then used to ‘seal’ the stone. It is the latter part of the Opticon treatment which has made it unpopular – many customers see this as being akin to ‘gluing’ a stone together. Most emerald treated with Opticon will just use the resin part of the procedure, which is acceptable if disclosed.
Detection of a treated emerald is best left to a qualified gemmologist. Oil and Opticon may be identified either through the use of magnification, UV radiation or thermal probe.
Also routinely treated is the other most often encountered member of the beryl family: aquamarine. Untreated aquamarine typically has a blue/green (aqua) appearance but it may also have a greenish-yellow or brownish-yellow appearance and it is this material which is most often treated. Stones are heated to between 400-450 degrees Celsius to produce a straighter blue colour. This treatment is permanent and the vast majority of aquamarine on the Australian market should be assumed to have been heat treated.
Morganite is a less commonly encountered gemstone on the Australian market. Pink is the desired colour but rough material may require heat treatment in order to drive off an orange or yellowish tinge. This is achieved by heating to between 250 and 500 degrees Celsuis (400 degrees or less is most commonly used).
The treatment of gems in the beryl group may be widespread but they do require correct disclosure to the consumer. This is particularly the case with emeralds where failure to disclose may result in a customer turning up to your store, days, weeks or months after purchase demanding to know why their stone no longer resembles the one they originally purchased.
The case in the US illustrated not just the lengths that a dissatisfied consumer will go to, but the cost to your business in not being forearmed with the right education.
ARTICLE SUPPLIED BY THE GEMMOLOGICAL ASSOCIATION OF AUSTRALIA. VISIT WWW.GEM.ORG.AU