Just about every "diamond dealer" uses the technical terms created by the Gemological Institute of America (GIA). But some unscrupulous dealers say their stones are much better than they really are. Some of them simply do not know how to grade accurately; others exaggerate to sound good. Either way, you could easily end up with LESS than you bargained for.
These days there are many ways to artificially treat diamonds to hide their visible imperfections. Diamonds can be fracture filled, laser drilled, or coated. Many dealers won't tell you if your diamond is treated, even though some of these treatments aren't permanent. This deception means you're paying far too much for the quality you've really gotten.
The ads you've seen for "one-carat total weight" diamonds or "half carat engagement rings" may be deceptive. The weights are rarely exact, and often are exaggerated. Total weight means the weight of the sum of ALL the stones--so it's hard to know what you've really bought. This practice is not only deceptive, it may also be illegal.
Many "SHARKS" also inflate their prices beyond fair market value so that they can mark them down, and legitimately claim "50% OFF!" It may be legal, but it sure is deceptive.
Who Can Appraise Your Diamond
There are no federal, state or local laws regulating who can appraise jewelry. Only qualified appraisers, not affiliated with a jewelry seller, can be independent. An honest and accurate appraisal should be an independent one. Don't be afraid to ask!