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Topaz with gemstone treatments
Gemstone Treatments

One topic that can be confusing for a gem buyer is the subject of gemstone treatments.  Most gemstones being sold today have been treated in some way and that’s not necessarily a bad thing.  The most common treatments are heating, irradiating, diffusion and dyeing. Many of the treatments are considered acceptable in the jewelry trade while others are not.  The important thing is that you know what you are buying so that you can make an informed decision.

The purpose of a treatment is simply to make a gem more beautiful than it would be without the treatment.  Generally, if the treatment is permanent, improves the qualities of the gem, is disclosed and is not meant to mislead the buyer, it is acceptable.

A few gems including Peridot, garnet, iolite are not usually treated,  but most others usually are.  For example, most all sapphires are heat treated to improve their color and clarity.  Heated sapphires display brighter, more even color that would be extremely rare in a natural stone.  Therefore most commercially available sapphires have been heated. That means you can a afford a more beautiful stone than you could if sapphires were not heated.  Some sapphires receive diffusion treatment to alter their color.  Through heat and pressure, a particular chemical element is diffused into the cut stone, thereby changing the color.  Many of the “padparadscha” (pinkish-orange) sapphire that is on the market was created this way.  However diffusion only effects a thin outer layer of the stone, so if the stone is chipped or scratched a little the original color will show.  This is an example of an “unacceptable” treatment.

 Some people like the idea of having an untreated stone. Part of the attraction of gems is that it is something created by nature, without any human manipulation. They prefer untreated stones even if it is more expensive or they have to sacrifice color or clarity a little.  Treatment is so commonplace that untreated gemstones are becoming rare and so, they may have more value to a collector or purest.

Below is a list of some of the treatments that are usually deemed “acceptable” by the jewelry trade:

  • heating sapphires and rubies
  • heating amethyst, citrine, topaz , aquamarine, tanzanite, tourmaline, and zircon
  • irradiating blue topaz
  • putting organic resins and wax in emeralds
  • waxing lapis lazuli, jade, and other opaque gemstones
  • dying onyx black

Many of these treatments are virtually undetectable, so whether or not they are treated is difficult to prove. Many stones are sold as “probably treated” and you should assume the stones you are buying are, unless it is specified as “untreated”.  You may see the term “natural used”. The term “natural gem” means that the stone was formed in the earth, whether or not it has been treated.  This is in contrast to synthetic, man-made or lab created.   

These are some of the gemstone treatments that are usually considered to be  “not acceptable”:

  • diffusion treatment of sapphire
  • glass filling of ruby
  • epoxy resin in emerald
  • dyeing lapis lazuli blue, or most other dye treatments
  • epoxy treatment of jadeite

Even these treatments are not illegal or even unethical as long as they are disclosed.  Ultimately, it is a personal decision whether you buy a treated, untreated or synthetic gemstone.  The important thing is that you know what you are buying.