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Colored Stone Grading - Enhancement

A gem enhancement (or treatment) is defined by the AGTA Gem Information Manual as "any traditional process, other than cutting and polishing, that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone." If a gem is enhanced by any method, it will be stated on our grading report using the AGTA nomenclature.

Some forms of enhancement, such as heat treatment, are more common than others, and are accepted as normal trade practice. Similarly, some enhancements have a greater effect on price than others. You can learn more about the various types of enhancement on our gem treatment page.

The overall quality grade of a stone may or may not be affected by normal or common enhancements. Because aquamarine is normally assumed to be heat-treated, the quality grade is not affected by this enhancement. On the other hand, the degree or level of enhancement can be a very important factor in the overall quality grade. Natural emeralds may have no more than minor enhancement to be considered fine or extra fine.

In cases where no enhancement is present in a gem that is normally enhanced, the overall quality grade (and stone value) may be substantially higher because of the added rarity of such material. A separate pricing structure has developed for fine and extra fine untreated Burma rubies, Kashmir and Burma sapphires and for extra fine emeralds. An extreme example of this can be seen in recent markets for Burma ruby, where prices have been extremely volatile at the upper levels - witness the record setting price of $425,000 per carat paid for an unheated 8.62 carat Burma ruby in the spring of 2007! We see similarities in the current market for extra fine emeralds, where some dealers will make repeated cleanings of an emerald to remove any traces of oil or resin. Extra fine emeralds with the coveted "no treatment present" designation from a top tier lab such as GIA command a premium.