GIA’S 4CS GUIDE
Beautiful. Rare. Cherished. Few gemstones hold the same enduring allure as a diamond. Each one is unique, with natural characteristics that influence its beauty, rarity, and value. As the creator of the 4Cs and the International Diamond Grading System™, GIA remains the world’s most trusted authority for unbiased diamond grading. This guide is designed to help you choose with confidence and clarity.
Diamond Colour
The colour evaluation of most gem-quality diamonds is based on the absence of colour. GIA’s D-to-Z Color Grading System measures the degree of colourlessness by comparing a diamond, under controlled lighting and precise viewing conditions, to masterstones of established colour value. Many distinctions are subtle to the untrained eye, yet they can have a significant impact on quality and price.
Diamond Clarity
Internal inclusions and external blemishes are part of a diamond’s natural formation and history. Clarity is assessed according to the size, location, visibility, and number of these characteristics, as well as their effect on the stone’s overall appearance. While very few diamonds are perfectly pure, greater clarity is generally associated with greater rarity and value.
Diamond Cut
Cut plays a defining role in a diamond’s beauty, influencing how it returns light to the eye. Of all the 4Cs, it is often the most technically complex to evaluate. For standard round brilliant diamonds in the D-to-Z colour range, the GIA Cut Grading System considers seven components: brightness, fire, scintillation, weight ratio, durability, polish, and symmetry.
Diamond Carat Weight
Carat weight refers to a diamond’s weight, with one metric carat equal to 200 milligrams. All else being equal, larger diamonds are rarer and often more valuable. However, two diamonds of the same carat weight can differ greatly in beauty and price depending on their cut, colour, and clarity.