Lab-grown diamonds are graded using the same criteria as natural diamonds. The most common grading system for both types of diamonds is the "Four Cs" – Cut, Colour, Clarity, and Carat Weight. These factors help determine the quality and value of the lab-grown diamond:
- Cut: The cut of the diamond refers to how well it has been shaped and faceted. The quality of the cut directly influences the diamond's brilliance and sparkle. Grading the cut involves assessing the proportions, symmetry, and polish of the diamond.
- Colour: Lab-grown diamonds come in a range of colours, from colourless to fancy colours like blue, yellow, or pink. The colour is graded on a scale from D (colourless) to Z (light yellow or brown), with higher grades being more valuable.
- Clarity: Clarity refers to the presence of internal and external flaws, known as inclusions and blemishes, respectively. The clarity grade assesses the number, size, and visibility of these imperfections. Diamonds with fewer and smaller inclusions receive higher clarity grades and are more valuable.
- Carat Weight: Carat weight is a measure of the diamond's size and weight, with one carat being equivalent to 200 milligrams. Larger lab-grown diamonds generally have higher value, but other factors like cut, colour, and clarity also affect the overall grading.
Additionally, some grading laboratories may provide information on the diamond's fluorescence, which refers to how the diamond reacts to ultraviolet light. Fluorescence can influence a diamond's appearance and may be noted on the grading report.
The grading of lab-grown diamonds is typically conducted by reputable gemological laboratories, such as the Gemological Institute of America (GIA) or the International Gemological Institute (IGI). These laboratories issue grading reports that provide detailed information about the diamond's quality and characteristics, ensuring transparency and confidence in the purchase. Consumers can use these reports to compare and evaluate different lab-grown diamonds and make informed decisions based on their preferences and budget.