How To Sell Diamonds
Get your diamond appraised by two or three jewelers for an accurate idea of the diamond's value. Instruct the appraiser that you want a Rapaport Value. Rapaport value means wholesale value of the diamond and it tells you the highest price you can sell your diamond for. If your diamond has no certificate, get a cerification from GIA. Doing so may help you to fetch a higher price.
Initially, try to sell the diamond yourself to those who know you like friends or family members. If not, then look for outside sources but avoid pawn shops. Pawn shop will offer 10% of what the diamond is worth! Also, do not offer to sell on consignment as things can go wrong since there is no shortage of diamond scams - even with jewelry stores.
You should be considering of auction it off through one of the famous auction houses such as Christie's or Sotheby's. Or if yours is not 'important' diamond or high-end diamond, then you can try selling it to individual in classified ads or in eBay. Lastly, try jewelry store but the jeweler might say your diamond is poor quality or low weight. That is where your appraisal or certificate comes in handy.