GIA’S 4C’s GUIDE TO UNDERSTANDING DIAMOND QUALITY
Beautiful. Rare. Cherished. There is no gemstone quite like a diamond. Each one is unique. And each has specific qualities that establish its value. As creator of the 4C’s 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.
GIA Colour Scale
The colour evaluation of most gem-quality diamonds is based on the absence of colour. The GIA Colour Grading System measures the degree of colourlessness by comparing a stone, under controlled lighting and precise viewing conditions, to master stones of established colour value. Many diamond colour distinctions are so subtle they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price.
GIA Clarity Scale
Internal ‘inclusions’ and external ‘blemishes’ result from the diamond’s natural formation process deep in the earth. Evaluating diamond clarity involves determining the number, size, relief, nature, and position of these characteristics, as well as how they affect the overall appearance of the stone. While no diamond is perfectly pure, the closer it comes, the higher its value.
GIA Cut Scale
The quality of cut is crucial to the diamond’s final beauty and value. Of all the 4C’s, it is the most complex and technically difficult to assess. The GIA Cut Grading System for the standard round brilliant diamond evaluates seven components: brightness, fire, scintillation, weight ratio, girdle thickness, symmetry, and polish.
Carat weight is the measurement of how much a diamond weighs. A metric “carat” is defined as 200 milligrams. All else being equal, diamond price increases with carat weight, because larger diamonds are rarer and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the 4C’s: clarity, colour, and cut.