First, find any documents you may have regarding your diamond purchase. Receipts, appraisals, grading certificates, all help in establishing value for your diamond. A diamond with an appraisal from a GIA graduate gemologist adds value to your diamond as it states the retail replacement value at the time the appraisal was accomplished and it also states the existence of a grading certificate. A grading certificate from a national gemological laboratory such as the IGI, AGL, or GIA can add value to your diamond as it accurately describes your diamond and provides a base for its value. Receipts from the initial purchase are also valuable as they can establish price at time of purchase.