Has anyone ever asked you this question – what is a diamond carat? Do you remember what your answer was? Even though we all hear this term so very often, few people can actually come up with the definition of the diamond carat. So, let me explain.
Jewelers sell diamonds by the carat (ct), which should not be mistaken for karat (kt), which in the US reflects to gold purity. Back in 1913 almost all countries came to an agreement that one carat should weigh 200 milligrams, or one-fifth of a gram.
However, prior to 1913, carats varied in weight depending on the country, and usually weighed more than the modern-day carats. For instance, the English carat did not have the same weight as the Indian. At the same time, the French carat was not comparable to both the English and the Indian carats. This may still be important to know, in case you are purchasing a vintage jewel that has the original sales certificate specifying the carat's weight. As the old diamond carats typically weighed more that the post-1913 carats, the old 3- ct stone would often weigh notably more than the modern 3- ct stone. These days, the term diamond carat represents the metric carat , or rather, the 200 milligram ct with five carats weighing one gram.
What are points ? Jewelers often speak about the diamonds' ct weight in terms of points. That is mostly true of diamonds weighing below one ct. One carat consist of 100 points, therefore, when a jeweler indicates a diamond weights 75 points, he means it weighs 75/100 of one ct, or c ct. So, a 25-point diamond is c ct, and a 10-point stone would be 1/10 ct.
Remember, the diamond carat is a measure of weight, and not the unit of size. This is particularly important to understand since so many people believe that a one-carat diamond represents a specific size. Here, most people would expect a one-carat emerald and a one-carat diamond to be of the same size. But, this is not the case. Emeralds weigh less than diamonds, and rubies, for instance, weigh more than diamonds. Therefore, the one-carat emerald will appear bigger than the one-carat diamond, while rubies will appear smaller than diamonds of the same weight.
Source by Val Kinsky