Diamond color actually means lack of color.

Understanding what diamond color means helps in choosing the right diamond. Interestingly, the diamond color evaluation of most gem-quality diamonds is based on the absence of color.

A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value.

GIA’s D-to-Z diamond 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.

Diamond clarity refers to the absence of Inclusions and blemishes.

The GIA Diamond Clarity Scale has 6 categories, some of which are divided, for a total of 11 specific grades.

• Flawless (FL): No inclusions and no blemishes visible under 10x magnification.
• Internally Flawless (IF): No inclusions visible under 10x magnification.
• Very, Very Slightly Included (VVS1, VVS2): Inclusions so slight they are difficult for a skilled grader to see under 10x magnification.
• Very Slightly Included (VS1, VS2): Inclusions are observed with effort under 10x magnification, but can be characterized as minor.
• Slightly Included (SI1, SI2): Inclusions are noticeable under 10x magnification.
• Included (I1, I2, I3): Inclusions are obvious under 10x magnification which may affect transparency and brilliance.

The cut of a diamond needs to be assessed from many dimensions.

Diamonds are renowned for their ability to transmit light and sparkle so intensely. We often think of a diamond’s cut as shape (round, heart, oval, marquise, pear), but what diamond cut actually does mean how well a diamond’s facets interact with light. 

Cut is rated on a scale of Poor to Excellent, and is mesured by three primary factors: brightness, fire and scintillation. GIA’s diamond cut grade also takes into account the design and craftsmanship of the diamond, including its weight relative to its diameter, its girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.

Diamond carat weight measures a diamond’s apparent size.

To put it simply, diamond carat weight measures how much a diamond weighs. 

A metric "carat" is defined as 200 milligrams. Each carat is 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. We 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 and eight carats".

All else being equal, diamond price increases with diamond 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 diamond 4Cs: Color, Clarity and Cut.

While now you know what carat means, it’s also important to remember that a diamond’s value is determined using all of the 4Cs, and not just carat weight.