The fear that most women face is having an important diamond switched by some unscrupulous jeweler, and most of time it has to do with sentiment. Possibly, the original engagement ring or a family heirloom.
Most jewelers are honest and ethical merchants. Some may charge more money than others (sometimes a lot more!), but morally speaking, switching doesn't happen with great frequency- but it can happen.
To safeguard you from having this experience, find a reputable appraiser who can give you a very definitive description of your diamonds. This should include the shape, millimeter dimensions, carat weight, color, clarity and cutting grades. The critical element is to have a plotted diagram- a blueprint of the diamond. This will show the internal and external characteristics of the stone- inclusions (size, configuration and location), blemishes, damage and any peculiarities. Having all of this will preclude anyone from possibly substituting your diamond with another.
In addition, should the diamond ever be stolen and recovered by an enforcement agency, you'll be able to claim your diamond with having this absolute identification, otherwise, it will be auctioned off at their next sale. If you choose not to obtain an appraisal, at least take a close-up photo of all of your valuables.
An American Gem Society Certified Gemologist or Certified Gemologist Appraiser is prepared and capable of handling this for you.
Dan Decker is a Certified Gemologist qualified to conduct appraisals on diamonds and jewelry.