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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 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.

The color evaluation of most gem-quality diamonds is based on the absence of color. 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 color value. Many diamond color distinctions are so subtle they are invisible to the untrained eye; however, these distinction make a very big difference in diamond quality and price.

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.

The quality of cut is crucial to the diamond’s final beauty and value. Of all the 4Cs, 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 more rare and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the 4Cs: clarity, color, and cut.

All diamond images and diagrams are for reference only and may not reflect true diamond quality grades or weight. Images and diagrams are not for diamond grading.