Carat Weight: One of the 4Cs of Diamond Quality

A carat is a unit of measurement which describes the physical weight of a faceted diamond. Before the carat was standardized, gem traders in the Middle East and the Mediterranean generally used carob seeds to balance their scales. During the Middle Ages, the carob seed was exchanged for other methods of weighing diamonds and other gemstones. The term carat is reported to have been used for the first time in England in the mid-15th century {cited}. Supposedly derived from the Greek word  keration (meaning carob seed), the word made its way through several cultures before being Anglicized {cited}. For all that time, there was no universal standard for classifying the weight of a diamond. It wasn't until October 1907, during the General Conference of Weights and Measures in Paris, that the current metric carat of 200 milligrams was considered for official adoption {cited}. According to the report, the French Ministry would introduce "a bill to legalize the 'metric carat' of 200 milligrams in that country, and to prohibit the use of the word carat to designate any other weight" {cited}. By 1913, the US adopted the metric carat, and once the Gemological Institute of America (GIA) established Carat Weight as one of the 4Cs of Diamond Quality, the term was well on its way to becoming universal. In terms of the 4Cs, Carat Weight is the simplest and most objective of the scales to determine. As the GIA notes, "It involves no estimates, no comparisons, judgments" {cited}. A diamond is placed on an approved scale and is typically measured to the hundredth decimal. This ensures an accurate reading by which to compare the stone to stones of similar size. A faceted diamond weighing more than 1.00 carats is a rare and glorious thing. According to experts at Lumera Diamonds, less than one in one million rough diamonds are large enough to produce a faceted 1-carat diamond. Due to their rarity, heavier diamonds are generally more expensive than lighter ones. Of course, as our previous discussions on the Cut, Clarity, and Color have revealed, determining the market value of an individual diamond is a bit more complex than that. Everyone knows that size matters. Larger diamonds sparkle more and attract more attention. If your intended has her heart set on a large diamond, then Carat Weight may be the most important scale to consider. However, there is a considerable amount of wiggle room between diamonds of very similar Carat Weight. For instance, a diamond weighing 0.99 carats will appear to be the same size as a 1.00-carat diamond, but the price might be considerably lower, depending on the diamonds Cut, Color, and Clarity grades. Furthermore, different shapes can make smaller diamonds appear larger. This can be a reflection of the diamond's actual physical dimensions (diameter) or it can be the result of an optical illusion. Either way, with certain diamond shapes and settings, you can choose a slightly smaller diamond that will appear just as large as a heavier diamond of a different shape. According to diamond experts, marquise-, oval-, pear-, and emerald-cut diamonds will appear larger than round- or square-cut stones of the same size, and well-proportioned diamonds will have a larger diameter, making them appear physically larger from the top and side than a deeper-cut diamond {Lumera Diamonds}. Although Carat Weight is the most objective of the 4Cs to determine, many subjective factors will play into your final decision. Purchasing a diamond is a monumental decision. It is to your benefit to sit down with a diamond expert and compare many different diamonds across the 4Cs. Take some time to compare several different diamonds of slightly different weights. Note how the visual impact of diamonds of varying sizes compares to the price differences between these sizes. Take note of how Cut, Clarity, and Color affect the overall brilliance of the diamonds you observe. Pay particular attention to how different settings can enhance the size of a smaller diamond. Looking at loose and set diamonds side by side will demonstrate the subtle, and not so subtle, differences between diamonds of varying sizes. We can't stress enough the importance of seeing in person as many diamonds as possible before making your final choice.