Carat

 

Diamonds are weighed in units called carats. A carat is measured in increments called points. One carat is equal to 100 points. Carat weight is the easiest of the 4Cs to determine because it is measured on a diamond scale. Two diamonds of equal weight can have very unequal value depending upon the cut, color and clarity of each.

Very small differences in carat weight can sometimes result in a disproportionate cost. To the naked eye, the difference between a 1 1/10 carat and 1 1/5 carat diamond might be impossible to discern, but the cost difference between those carat weights can be significant for otherwise comparable diamonds.

 

Color

 

Color refers to the body color of the diamond. Fancy color diamonds aside, the best, most beautiful color for a diamond is no color at all. The Gemological Institute of America (GIA) has created a scale to measure diamond color, ranging from D (colorless) to Z (yellow). Fancy color diamonds are graded Z and higher.

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Most VLM diamonds are graded "near colorless" - between G and J on the color scale. At a J grade and beyond, the human eye can start to detect a yellow tint.

D-color diamonds are very rare - and they cost a pretty penny. Moving down the color scale toward H or I lets you buy a diamond that still appears white, but is more common and thus, more affordable.

One thing to note: Color diamonds have become more valuable as they've become more fashionable, and "fancy" colors, when they occur naturally, are rare and expensive. (Diamond color treatments can help you get these coveted colors for less.)

 

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Clarity

 

Clarity is the degree to which a diamond is free from flaws, which can hinder light as it passes through your diamond.

Like people, diamonds have "birthmarks" that vary in size, shape, position, quantity and color. These birthmarks are known as inclusions (internal) and blemishes (external). Inclusions are formed deep in the earth during the diamond's growth. Blemishes can result from the diamond-cutting process.

The clarity grade is determined based on the size, number, position of, nature and color of the diamond's blemishes.

Though nearly all diamonds have inclusions and blemishes, the most prized diamonds are flawless.

The clarity scale, developed by the Gemological Institute of America (GIA), has 11 grades:

 

• F (flawless inside and out)

• IF (internally flawless, which means there are blemishes on the surface but not inside the diamond)

• VVS1 and VVS2 (very, very slightly included - two levels)

• VS1 and VS2 (very slightly included - two levels)

• SI1 and SI2 (slightly included - two levels)

• I1, I2 and I3 (included - three levels)

 

It may be difficult to see inclusions with the naked eye, depending on where they are located within the diamond. But every diamond is unique, so you need to look closely. If you view an SI2 diamond and can't see the inclusions without a jewelers loupe, you can probably accept a lower grade and save on cost without compromising beauty.

 

Cut

 

Of the 4Cs, a diamond's cut has the greatest influence on its fire, sparkle and brilliance, making it, arguably, the most important C. Cut refers not only to the shape of a diamond, but more importantly to its proportions (how the diamond's angles and facets relate to one another), symmetry (the precision of its cut), and polish (the surface of the diamond).

A diamond's cut is harder to quantify than color, clarity and carat weight. The cut of a diamond is determined by the master craftsman, who formulates the best way to shape, facet and polish the diamond to maximize its beauty.

A diamond is essentially a prism of light, and diamond cutters work to let light shine through each stone. When done well, a diamond's cut can be the most important C.

When grading the cut of a diamond, laboratories evaluate the diamond for its:

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Brilliance

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The intensity of the white light that is reflected, both from the surface of the diamond as well as from the inside.

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Fire

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Also known as dispersion, it's how the light scatters through the diamond to create a rainbow of light, like a prism.

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Scintillation

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These are the flashes of white light that are visible when you move your diamond. These flashes are also known as "sparkle."

When a diamond is "Ideal-Cut," it means the angles and proportions of the diamond have been cut to produce the ultimate sparkle, fire and brilliance.