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Rookie with loose emeralds and no knowledge.

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I recently purchased all of the loose emeralds from a long standing (50 years) family owned jewelry store in Hanford, Ca.  I know almost nothing about emeralds and have some rookie questions.

I understand that emeralds are normally oiled and I was curious about that process. Most of these won't need it as they were ready to be set by the store, but some may.  Do you have any reference materials or suggestions?

As for the emeralds, I have about 240 natural stones, most are small rounds but I also have pear, marquis and two larger, nice ovals. I also have 5 "created" 3x5 oval stones that are marked at $75 cost to the store and test as true emerald.  How should I treat / market these?

They're all in the ziplock bags the jeweler bought them in and some have notes about the stones or the jewelry store cost.  I don't mind pricing them at or just above the marked store cost as I bought them at auction for less, but I don't want to overcharge on the stones I don't have reference points on.  I do have decent (macro) photos on all of them.

Any help you can give is appreciated.

Daren  (Grandpa)

asked Jun 21, 2015 by Grandpa (120 points)
edited Jun 21, 2015 by Grandpa

1 Answer

0 votes

Natural emerald tends to be more heavily included than any other kind of gemstone. Most emeralds have not only numerous internal inclusions and fractures, but also tiny surface breaking fissures or cracks. For this reason, the vast majority of emeralds are treated to improve their clarity. This practice is widely accepted in the trade, but there is some controversy surrounding recent developments in emerald treatments.

The traditional treatment for emerald is oiling with cedar oil. Cedar oil is a natural product from cedar trees and is colorless and viscous. It can be produced in a very pure form and has a number of industrial uses. It is used as an immersion oil in light microscopy, as an ingredient in insect repellents, as an anti-bacterial and as a food preservative. It is also often used for its aromatic properties, especially in aromatherapy. Cedar oil has been used for fracture-filling emerald because it has a refractive index that is similar to emerald.

Since cedar oil is so sticky, it is not easy for it to penetrate the microscopic cracks in emerald. So it requires some heat and pressure to do the job. First the emeralds are cleaned, usually in an acid bath. Then the gems are placed in a heated hydraulic cylinder with pure cedar oil and locked tight. The heat liquifies the cedar oil and the pressure helps it penetrate any tiny cracks in the emerald.

After several hours the cylinder is left to cool. The stones are then removed and cleaned. The cedar oil that has penetrated the emerald returns to its thick, viscous state, making it very difficult for it to leak out without the aid of ultrasonic cleaners, excessive heat or harsh solvents.

Natural Emerald

Natural Emerald

Traditional oiling is stable but not permanent. Eventually an oiled emerald will require re-oiling to keep it looking at its best. Therefore, a number of attempts have been made to introduce more permanent fillers. These include natural and artificial resins (such as Opticon), polymers and prepolymers. The use of these new fillers has created some controversy, particuarly in cases when the exact filler has not been disclosed.

One important thing that consumers want to know is thedegree to which an emerald has been enhanced. This is perhaps even more important than the type of filler used. Some labs, such as the GIA (Gemological Institute of America) have tried to develop classification schemes that distinguish emerald enhancement as minor, moderate or significant, depending how many surface-reaching fissures have been filled.

answered Jun 21, 2015 by anonymous