Website: Address: 581 Fifth Avenue, New York, NY 10017 Phone: +1 (212) 207-4140 GSI diamonds are Inventory Integrity marked, which means they adhere to the strict requirements put forth by Gemological Science International. GSI diamonds are identified by trained experts who use advanced equipment and a strict process to ensure their quality. This fact alone separates Gemological Science International form others in the diamond grading industry because it is the only company to offer these services together. If you are shopping for a diamond, jewelry, or gemstone, make sure your piece is a certified GSI diamond. A GSI grading report can be made for every diamond. GSI diamonds Facebook: Instagram: Twitter: Pinterest: ©