GIA’s 4Cs Q&A series continues with a careful consideration of carat weight.

Q: What is the difference between carat and karat?

A: Karat (abbreviated “K” or “Kt”) is a unit of measure that describes the purity–or fineness–of gold.

Q: How did the carat system start?

A: The modern carat system started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. The carat is the same gram weight in every corner of the world.

Q: What are “magic sizes”?

A: Some weights are considered “magic sizes”–half carat, three-quarter carat, and carat. Visually, there’s little difference between a 0.99 carat diamond and one that weighs a full carat. But the price differences between the two can be significant.

Q: How is diamond carat weight measured?

A: To determine carat weight, the grader weighs the diamond using an extremely accurate electronic micro-balance that captures the weight to the precise fifth decimal place (the nearest ten-thousandth of a carat).

To see if your knowledge of carat weight measures up, please check out 4Cs of Diamond Quality or download the GIA 4Cs app, now available on iPhone, iPad, and Android!

Color Q&A | Clarity Q&A | Cut Q&A | Carat Weight Q&A

All diamond images and diagrams are for reference only and may not reflect true diamond carat weight.

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A metric “carat” is defined as 200 milligrams. Each carat can be subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. The diamond carat weight of a diamond below one carat can also be described by its ‘points’ alone. For instance, a diamond that weighs 0.25 carats could also be referred to 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.’

All else being equal, diamond price increases with diamond carat weight, because larger diamonds are more rare and more desirable. But two diamonds of equal carat weight can have very different values (and prices) depending on three other factors within the 4Cs: clarity, color, and cut.

In other words, knowing all the 4Cs inside and out makes you a much more educated and empowered diamond consumer. Wouldn’t you all agree?

Be sure to brush up on cut, clarity, color and the Diamond Grading Scales.

All diamond images and diagrams are for reference only and may not reflect true diamond carat weight.

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GIA created the 4Cs (Color, Clarity, Cut and Carat Weight) as a universal method for establishing the quality of any diamond, anywhere in the world. The 4Cs means two very important things: diamond quality can be communicated in a universal language, and diamond-buying consumers can know exactly what they are about to purchase.

All diamond images and diagrams are for reference only and may not reflect true diamond quality grade. Images are not for color or clarity diamond grading.

Interested in learning more about how to buy a diamond? Stay tuned for next week’s tutorial on diamond color or check out these great 1-minute videos on the 4Cs: Color, Clarity, Cut and Carat Weight.

The post GIA Diamond Grading Scales: The Universal Measure of Quality appeared first on GIA 4Cs Blog.

You can buy coffee by the pound. You can even buy deli meat by the pound. Even if you’ve never bought a diamond, the correlation between weight and price is a concept that we can all understand. Therefore, the general perception is that a larger diamond is more valuable than a smaller one.

Diamonds are measured or weighed in “carats”, or the equivalent of 200 milligrams. Precision in weighing a diamond is such that a diamond is weighed to a thousandth (.001) of a carat and then rounded to the nearest hundredth.

What is not as easy to understand is that a 2.00 carat diamond is not always worth twice as much as a 1.00 carat diamond. Large diamonds are rarer than smaller ones, so logically they seem to be worth more. But the value of a diamond is determined by considering all of the 4Cs of diamond quality as a whole.

Remember, when you are looking at diamonds, bigger is not always better. Learn about the next C, Diamond Color, before your next purchase.

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• Carat:  Diamonds are weighed in metric carats. Two carats weight about the same as a small paper clip. A carat is divided into 100 “points”, so a diamond of 50 points weighs 0.50 carats.

• Clarity:  Nearly all diamonds contain unique clarity characteristics.  Flawless diamonds are exceptional and costly. Most inclusions are invisible unless magnified.
• Color:  Colorless diamonds are extremely uncommon. Most diamonds have a slight yellow or brown tint. GIA uses letters to represent colors, beginning with D (colorless) and ending at Z (light yellow or brown). “Fancy colored diamonds” come in every color imaginable, are also very unusual and have their own GIA color grading system.

• Cut:  While diamonds come in different shapes, such as round, pear or marquise, the term “cut” refers to proportion. The well-cut, balanced diamond has unbridled brilliance, sparkle and fire.

Below is a suite of diamonds including, (clockwise from top) Asscher cut, pear shape, marquise shape and round brilliant cut. These diamond shapes remain popular in today’s diamond market. Photo by Robert Weldon, © GIA 2008

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