The 4Cs of diamond quality is a language jewelers everywhere use to describe the attributes of a diamond, that when taken together, help to determine its overall quality. Quality is ultimately tied to price, so it’s crucial that you learn the 4Cs so that you understand what you’re buying:
Diamond Carat Weight Measures a Diamond’s Apparent Size. Diamond 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 diamond carat weight because larger diamonds are more rare and more desirable.
Each carat can be subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweler may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as ‘one point oh eight carats.’
Diamonds are created by nature under tremendous heat and pressure. Nearly all diamonds contain unique internal characteristics called inclusions and external characteristics called blemishes. Many clarity characteristics are too tiny to be seen by anyone other than a trained gemologist using magnification. The GIA Clarity Scale contains 11 grades ranging from Flawless to Included.
Truly colorless diamonds are very rare and highly valued. The GIA Color Scale uses letters to represent the absence of color, beginning with D (colorless) and ending at Z (light yellow or brown). Color distinctions can be quite subtle and only visible to the trained eye, but the differences can have a significant impact on price.
While diamonds can be fashioned into different shapes, the term “cut” refers to how a diamond’s complex proportions and angles relate to light. A number of factors influence a diamond’s cut grade, including its overall face-up appearance, design and craftsmanship. The GIA Cut Scale for standard round brilliant cut diamonds ranges from Excellent to Fair.