You have probably heard of the “Cs” used to describe diamond quality. Carat Weight, Color and Clarity have been used on paper since the 1930s to judge diamonds. In this tutorial we will present important information about the traditional 3 Cs, and critical information on CUT, the 4th C, that may change the way you look at diamonds.
The weight of a diamond is expressed in carats. This term comes from ancient times when gems were weighed against the carob bean. One carat is equal to 200 milligrams, or one fifth of a gram.
Carat weight is sometimes expressed in points. One point equals 1/100th of a carat, so 25 points is equal to a quarter of carat and 50 points is equal to half of a carat. Grains of rice were also used. 4 grains of rice were equal to a carob bean. That’s why people sometimes call a quarter carat diamond a one grainer.
As carat weight gets larger the value of the diamond increases disproportionately. This is because pieces of rough material are increasingly rare with size. Over a million pieces of rough must be mined to find one piece large enough to produce a 1 carat finished diamond. This means that a diamond twice as large as an identical, smaller one may be three or more times as expensive, depending on the market.
Prices per carat change at certain size thresholds. For example, the price per carat will be less for a .90 F VS2 diamond than the price per carat for a 1.00 F VS2, which will be less than the price per carat for a 1.50 F VS2 diamond, even though the color and clarity are the same. If the diamond of your dreams is above your intended budget, you may want to think about purchasing a diamond of the same color and clarity just under the threshold of the weight that you have in mind. Of course, diamond manufacturers are aware of these price-making weights too, so most diamonds are produced to finish at or just above such thresholds.
Carat weight is not the same thing as size. As diamonds increase in weight their apparent size becomes less predictable. Diamonds cut too shallow may appear larger than they should, while diamonds cut too deep may look smaller. Too shallow and too deep are both undesirable. In this example bigger is not better.
You should always use millimeter measurements and consider girdle thickness when judging proper spread for carat weight.
(Not an exact representation of corresponding carat sizes)
Superior cut can also result in edge-to-edge light performance. A well-cut diamond will appear larger than other diamonds of the same carat weight and spread (this will also be addressed later, in our CUT tutorial).
(Photo courtesy, Garry Holloway)
- Know what size the recipient desires.
- Research what that person’s friends have.
- Local expectations vary (East Coast, West Coast, Midwest, etc.).
- Spread should be correct for carat weight.
- Seek great diamond CUT for edge to edge light return.
- Finding a diamond just under a certain size threshold may save money.
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