Treatment: Natural stones may be made to undergo processes to improve or change their appearance. The changes are usually made to improve the color or clarity and to cover open or closed fissures.
Common treatments include: Heating, Filling or In-Filling, Irradiation, High Pressure High Temperature, etc.

Disclosure: Stating the weight, type of stone, price, and so on all constitute disclosure. When a stone has been modified in some way other than cutting and polishing, this additional process should also be disclosed. Unfortunately, some sellers think that if they disclose a treatment it will hinder or prevent the sale. It is on this point that problems have arisen over how to enforce “disclosure” in the gemstone industry.… There is general agreement that some treatments do not have to be disclosed. The argument runs that some processes are universally used on certain types of stone, such as oiling emeralds, staining agates, heating aquamarines, etc. These are termed accepted trade practices. Stones that have undergone other treatments must be listed as “treated,” or the actual process described.…
As a general rule, if treating a stone increases its value, the treatment should be disclosed. Enhancement is a term that has crept into the lexicon as a substitute for the word “treated.” … But these two terms have now taken on special meanings within the trade. Stones subjected to “softer” treatments that can be classified as “accepted trade practice,” such as waxing, mild heating and filling with colorless oils and resins, are now referred to as enhanced. Others would like to use the term enhanced for certain treatments that are irreversible. Unfortunately there is little agreement on where to draw the line, so there is inconsistent use of the terms “enhancement and treatment” within the trade.

Process: This is a term that has come into the lexicon to replace both treated and enhanced. The argument is that all stones are subjected to processes from the time they are mined, such as cutting and polishing, and some stones need further processes, such as heating and fracture filling, to make them salable. Unfortunately the use of this term does not eliminate the need for disclosure, as others argue that some processes have to be specified and disclosed.

Certificates: These are documents produced by gemological laboratories to identify a stone. They usually state the type of the stone, its dimensions, weight, color (when this is needed to identify a specific stone), any treatments, and sometimes the origin of the stone. These certificates do not grade stones on their color, quality of cut, inclusions (except for identification purposes), and other features that might affect the value.

Grading Reports: These documents are produced by laboratories to rate a diamond’s color, clarity, and so on. These reports are often referred to incorrectly as “certificates” or “diamond certificates,” but the correct terminology is “(Diamond) Grading Report.” This confusion has had serious consequences recently in the debate over synthetic diamonds. People who did not want synthetic diamonds to be graded by color and clarity referred to the grading reports for these stones as diamond certificates—a serious error, as those making this argument certainly do want a certificate to state that a particular stone is synthetic.

Origin: Some laboratories have the ability to detect the origin of gemstones, or in other words state where they were mined. Skill and a large database are required. For colored stones, this is usually done by identifying the exact shade and type of inclusions. This process can be important because some in the trade value stones of a certain origin highly. Thus, Burma rubies and Kashmir sapphires have a greater value than the same type of stones originating elsewhere. This is a controversial topic within the trade.