Your Guide to Diamond Quality: Carat Weight

When you’ve been in the jewelry business as long as I have, the lingo starts to become second nature. I describe diamonds by their brilliance and fluorescence, and can rattle off their carats and points. I know what makes a diamond VS-1, and what an F-color stone looks like. This is knowledge that I have gained through my years of practice and history with jewelry.

But to the average consumer, all of these unfamiliar terms can make the diamond market intimidating and hard to navigate.

When shopping for diamonds, you want to ensure that you get the best quality for your budget. But what makes a high quality diamond? How is quality determined? And who, exactly, does the determining?

It all starts with the GIA and the implementation of the 4Cs system.

What are the 4Cs? 

The 4Cs are a system created by the Gemological Institute of American (GIA) that is used for grading diamonds. The GIA was established in 1931, and has since become the world’s foremost authority on diamonds, colored stones, and pearls. 

Before the formation of the GIA, there was no standardized system for grading and ranking diamonds and other stones. This, naturally, allowed for confusion over what made a quality stone, and also allowed for fraud; it was almost impossible to know that what you were getting was exactly what you were paying for.

In the mid-20th century, the GIA unveiled its 4Cs method of grading, with the goal of providing a universal language for understanding diamond quality when purchasing. It has since become a method that is used universally within the jewelry industry. 

Each of the 4Cs stands for one of the criteria within the method: Color, Clarity, Cut, and Carat weight. Each analyzes a different element of a diamond; the highest quality diamonds will be exceptional in each of these four areas. While many people tend to focus on carat weight as the most important element in picking a diamond, we often find that bigger isn’t always better.

Choosing the right diamond

So, What Exactly is Carat Weight?

Carat weight measures how much mass a diamond or other stone has. It is a measure of weight, not size. A metric “carat” is set at 200mg, meant to provide consistency across different systems of measurement. Each carat is divided up into 100 points, used to provide accurate measurements to the hundredth of a decimal place. This is especially helpful for carats that weigh less than a carat; jewelers will refer to these diamonds by their points. For example, a diamond weighing 0.25 carats will be referred to as a “twenty-five pointer”. 

It’s fairly easy to measure carats in the jewelry world, especially because it is the most objective of all 4Cs. All you need to measure a stone’s carat weight is a highly calibrated scale capable of measuring very small weights. You can buy one of these scales fairly cheaply, but the most accurate will be more expensive. Organizations such as the GIA or AGS will use highly accurate scales. 

Carats are a universal measurement used to weigh gemstones, and it doesn’t always indicate the size of the stone. Gems of different density can have different carat weights, even if they measure the exact same size. Cut can also influence the size of the stone, making it appear larger or smaller than it’s carat weight suggests. This means that a 2 carat diamond will not necessarily be twice the size of a 1 carat diamond. 

But Why Does This Matter? 

Carat weight is seen as one of the most important aspects in determining the cost of a diamond, for one very simple reason: the larger the diamond, the higher the cost. 

Larger diamonds are more rare and more desirable to those shopping for gemstones. Nature more often produces diamonds of a smaller carat than diamonds larger than a carat. This rarity has created a premium on large diamonds, as well as an exponential increase in price. A 1 carat diamond will cost more per carat than a 0.50 carat diamond, and a 2 carat diamond will cost more per carat than a 1 carat diamond. 

So, What Can I Do To Get The Most Bang for My Buck?

There are a few things you can keep in mind when shopping for diamonds: 

  1. Diamonds weighing just below the main carat thresholds (ex. .9 carats vs 1 carat, 1.8 carats vs 2 carats, etc) will be slightly discounted. 

Since the carat weight measures the mass of the diamond, it is possible that a 1.8 looks the same size or even larger than a 2 carat, depending on the cut and face size of the stone. 

  1. Choose a diamond shape that has a larger face. 

A round brilliant shape generally looks the largest among the various diamond shapes due to its weight distribution. The face of a round diamond is the largest measurement of the diamond, and it is cut in a cone shape below the face. This is the part of the stone that is hidden in the jewelry setting and not as important to have mass. 

  1. Choose a diamond shape that is more forgiving on diamond quality to the naked eye.

For instance, an emerald-cut (rectangular) diamond has a “step cut” with fewer facets than a round brilliant-cut. This allows inclusions in the stone to be seen with the naked eye much easier than a stone with a round brilliant (many facets) cut. A higher quality clarity is required on stones with less facets (asscher, emerald) which will result in higher pricing. 

  1. Choose a diamond with inclusions on the side of the stone that won’t be as noticeable or can be hidden with a prong. 
  2. Fluorescence

Stones that glow under UV light in the slightest are graded as having fluorescence. This quality can lead to a diamond looking cloudy ~ a quality that won’t be highlighted in any GIA report. This is an example of why it is crucial that you work with a trusted jeweler who can identify these issues on your behalf. Although fluorescence can make a diamond look milky, many times they don’t affect the stone. And sometimes, fluorescence can even make the color of a diamond appear whiter. Since fluorescence results in a discount to a diamond, it could result in favorable pricing without any negative impact to the stone’s appearance.

Carat weight is just one aspect in determining the quality of a diamond; bigger isn’t always better, in this case. When purchasing, you also want to look at the brilliance within the diamond, the fire. You want a diamond that will turn heads. Relying solely on carat weight may lead you to not consider a much higher quality diamond. Be sure to educate yourself before diamond shopping, and make sure you work with a jeweler who can answer all your questions and makes the process easy for you to understand.

Want to Learn More?

Check out these additional resources for more on carat weight and other aspects of the 4cs:

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