4C's: Carats

PostBy Avi Paz Group At 01.08.2010

Diamonds, like all precious stones, are measured in carats. The carat dates back to ancient traders in the Mediterranean, who used wheat grains or carob seeds – whose size variation is extremely slight – to weigh precious stones. The Arabic word for carob is quirat. In Greek, carob is keration, from which the modern term "carat" is derived.

In Europe, a carat was designated equal to 4 grains Troy weight (205.3 milligrams). This system remained in place until the carat was assigned a standard metric weight of 200 milligrams, which was adopted in the US in 1914.

A carat in the context of other common weights:
• 1 carat = 200 milligrams
• 1 carat = 0.20 grams
• 1 carat = 0.007 ounce
• 141.7 carats = 1 ounce

Carats are the most significant factor in pricing a diamond, but the cost of a stone is based on a per-carat system. The cost of each carat in a given diamond is added up in the total carat weight, which does not remain fixed. The per-carat cost actually rises exponentially, since heavier diamonds are rarer than smaller diamonds. The larger a diamond is, the larger its per-carat price will be.

The carat measurement is further subdivided into points – with each carat containing 100 points. A half-carat diamond is also a 50 point diamond, and a 75 point diamond is a 3/4 carat diamond, etc.
The Rapaport Report trade publication provides the industry with a per-carat price guide, taking into account a diamond's cut, color, and clarity.

Carats are also the units used to measure rough diamond production. Production – whether by nation, region, or individual mine – is listed in carats and then valued in dollars. As a point of reference, the Annual Global Summary for 2009 released by the Kimberley Process Certification Scheme cited the Russian Federation's rough diamond production for that year as 34.7 million carats worth $2.34 billion.