Why is this important for you, as a seller of a diamond? Because diamonds that have been certified by the GIA as a certain color and clarity (among many other important factors) are worth more than an appraisal letter from a local jeweler. Even if you have a certificate from another laboratory, like EGL or IGI, they don't carry the weight of a GIA certificate. If you have a fine diamond, one carat or larger, it is surely worth spending the money to have a GIA certificate issued. The cost, including shipping for a one carat diamond is normally around $200, but the certificate, if the diamond is better than an I1 clarity and better than a K color, is normally worth it.
You will also be able to scan and email the certificate to many potential buyers who will give you solid bids without seeing your diamond in person. The drawbacks are that the GIA does not grade diamonds in mountings so you have to pay a jeweler to take the diamond out of the mounting and put it back in when the grading is finished.
From the Gemological Institute of America (GIA) website: "Established in 1931, the Gemological Institute of America is the world’s foremost authority on diamonds, colored stones, and pearls." They have educational courses for anyone to take and are considered the best resource in the country for information about diamonds and colored stones. In the diamond business, if your diamond has been graded by GIA, the marketable price is established by market conditions and nothing else.
