GIA’S 4CS GUIDE

Beautiful. Rare. Cherished. There is no gemstone quite like a diamond. Each one is unique, with specific qualities that establish its value. As creator of the 4Cs and the International Diamond Grading System™, GIA is the global authority and trusted source for unbiased diamond quality assessment. This guide is devoted to helping you choose both well and wisely when shopping for a diamond.

Diamond Colour

The colour evaluation of most gem-quality diamonds is based on the absence of colour. The GIA Color Grading System measures the degree of colorlessness by comparing a stone, under controlled lighting and precise viewing conditions, to masterstones of established colour value. Many diamond colour distinctions are so subtle they are invisible to the untrained eye, yet they make a significant difference in quality and price.

Diamond Clarity

Internal ‘inclusions’ and external ‘blemishes’ result from the diamond’s natural formation process deep in the earth. Evaluating diamond clarity involves assessing the number, size, relief, nature, and position of these characteristics, as well as their impact on the stone’s overall appearance. While no diamond is perfectly pure, the closer it comes, the higher its value.

Diamond Cut

The quality of cut is crucial to a diamond’s final beauty and value. Of all the 4Cs, it is the most complex and technically difficult to evaluate. The GIA Cut Grading System for standard round brilliant diamonds considers seven components: brightness, fire, scintillation, weight ratio, girdle thickness, symmetry, and polish.

Diamond Carat Weight

Carat weight refers to how much a diamond weighs. A metric carat equals 200 milligrams. All else being equal, the price of a diamond increases with carat weight, as larger diamonds are more rare and sought-after. However, two diamonds of equal carat weight can vary greatly in value based on clarity, colour, and cut.