1st Feb 2014
The Not So Sexy Side of Emeralds (read it anyway)!
We have spoken about the mesmerizing color of certain emeralds and how, for this stone, it’s all about color. But there’s more to it than that.
Spoiler alert: to buy an emerald there are other technicalities to consider.
This is one of those need-to-know articles.
The first decision is to whether to require a gem certificate or not. If you want a pretty stone (remember Columbian green or blue green, not grassy green, are most desirable) then a certificate is not necessary. Just make sure you know the most desirable colors which you can study on the Internet by googling Columbian emeralds.
There are many important stones sold without a certificate because getting one requires time and money and the price goes way, way up. Serious collectors should ask to see the certificate in case there is one or considering getting one commissioned. The certificate will authenticate the origin of the stone. For example, a certificate, preferably from AGL (colored stone experts) would denote Columbia versus Africa as to the source of the stone.
We have spoken about heat treatment before. Generally speaking, a natural, non heat treated stone will have more inclusions known as mossy type structures and/or crystal “feathers”. This is to be expected. This also means the color is absolutely the organic and true color of the stone. Emeralds, even heat treated ones, will have inclusions.
An eye clean emerald is rare (meaning no inclusions visible to the eye) and is very likely to be heat treated because the crystalline composition of this stone almost always has inclusions. That is perfectly fine for this stone, just know that is what it is, regardless of what you may be told.
Below is a sample chart of the degree of heat treatment classified according to minor, moderate, and significant. Minor heat treatment or no heat treatment is the most expensive kind of emerald to buy. The chart below, by the Gemological Institute of America, shows the clarity of the stone by degree of heat treatment.