The most obvious and logical way to tell if a diamond is real or not is to get the diamond appraised. To get a better understanding of the worth of your diamond and to validate the accuracy of the appraisal, I recommend seeing multiple appraisers.
Something to remember when purchasing diamonds - always check the authenticity and ask for a certificate. If you ever find out that you purchased an imitation diamond, you may have a difficult time getting your money back. Some stores know exactly what they're doing when they sell you a fake diamond, and some stores genuinely think it's real. Whatever the case, you may get accused of switching the real one with a fake one so a certificate of authenticity will greatly help your case. Also, always remember that no two
diamonds are alike.