It is highly recommended to buy a diamond with an independent grading report or certificate.
Grading reports do not give a value like appraisals do. Instead an independent expert opinion is provided on the quality of loose or unset gems. Most grading institutes support worldwide labs or services and do not sell diamonds.
Each lab will grade diamonds slightly different. Samuel Kleinberg prefers GIA and AGS labs for certifying its diamonds.
Unaffiliated with any retailer, wholesaler, or manufacturer, GIA provides impartial diamond analysis. GIA's procedures are designed to achieve utmost accuracy. Each diamond is inspected by renowned diamond graders and gemologists. Reports detail an assessment of the 4Cs - colour, clarity, cut, and carat weight. In addition, grading reports contain a hologram, security screen, and microprint lines, as well as bonus security features that exceed industry requirements.
AGS - American Gem Society Laboratories
The AGS Laboratories is the only diamond-grading laboratory backed by the industry's premier consumer protection agency, the American Gem Society. As a preeminent authority in diamond grading, AGS Laboratories provides reports for diamonds of all sizes using a succinct 0 to 10 grading scale. Known for implementing the strictest requirements and highest standards, AGS Laboratories employs leading-edge research and technology.