The standard unit of weight for diamonds and other gemstones, carat weight is measured at the GIA Laboratory using a highly precise electronic scale, rounded to the nearest hundredth of a carat.
A diamond’s carat weight is the measurement of how much a diamond weighs. One metric “carat” is defined as 200 milligrams or 0.2 grams, or approximately 0.007 ounces. Five carats equals 1 gram, and 141.7 carats equals 1 ounce.
Carat weight is commonly expressed in “points” or fractions. Each carat can be 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. For instance, the jeweler 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 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 of the diamond 4Cs: clarity, color, and cut. It’s important to remember that a diamond’s value is determined using all of the 4Cs, not just carat weight.
History of the Carat:
So why do they call this unit of measurement a “carat”? Does it have anything to do with the orange colored vegetable? Nope! In ancient times, when units of measurement like grams and ounces had not yet been invented, some sort of standard was needed so people could establish the value of a given item.
In the Mediterranean area, there is a tree called a “carob” tree. The carob tree bears fruit called carob beans. These long green beans have seeds inside, all of which are nearly identical in size. And because of their supposed uniformity the ancient Mediterranean traders turned to the carob seed as a unit of measurement. A gemstone would be placed on one side of a balance scale and the other side would have carob seeds on it. A stone that balanced out evenly against 5 seeds was said to weigh 5 seeds – which later evolved into 5 carobs – and later into 5 carats.
In 1871, the British were establishing what we now know as The Old English Weights and Measures. They found that a carob seed from one side of the Mediterranean weighed 0.1885 grams while carob seeds from the other side weighed 0.215 grams. Over time, between 1878 and 1889, these two numbers were averaged, and the number 0.204304 grams was used. Subsequently, several trees had all of the beans stripped from them and their seeds counted and weighed, the average weight was 0.197 grams. This was rounded to 0.2 grams and is still used today.
A paragon is a perfect diamond- flawless and without inclusions. In the 16th century, a mass of twelve carats was sufficient to qualify for this designation, but today the threshold lies at 100 carats.
The largest flawless diamond in the world is known as The Paragon, a D-class gem weighing 137.82 carats, it is the tenth largest white diamond in the world. The gem was mined in Brazil and attracted attention for being an exceptional white, flawless stone of great size. The Mayfair-based jeweller Graff Diamonds acquired the stone and cut it into an unusual seven-sided kite shield configuration, and set it in a necklace which separates to both necklace and bracelet lengths. Apart from the main stone, this necklace also contains rare pink, blue, and yellow diamonds, making a total mass of 190.27 carats.
Like us on Facebook for updates and images of our original jewelry designs and come back in 2 weeks to continue your diamond education; our next post will focus on Clarity.