The Essential 4C's
Instead of grams or kilos, diamonds are weighed in carats (not to be confused with gold’s Karat which signifies purity). This simply denotes a measuring scale where each 1 carat = 0.2 grams (0.50 carat = 0.1 gram and 5 carats = 1 gram).
As the carat weight increases, so does the size of a diamond. However, confusingly, this relationship is not a linear but rather a curve – so a 2.0ct diamond will not appear twice as big as a 1.0ct diamond as shown below.
Diamond Carat Weight Measures a Diamond’s Apparent Size
A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweller may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweller 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 rarer and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4C:
Carat , Colour , Clarity , and Cut.
All diamonds and precious stones RUBY , SAPPHIRE , EMERALD etc. are weighed in carats (not to be confused with gold’s Karat which signifies purity).
Some diamond sizes are highly sought after.
( eg 0.50ct, 0.75ct,1.0ct) and prices can vary dramatically depending on their carat weight. A 0.90ct diamond may be 10-20% better in value than a 1.0ct diamond of the same quality, but may appear almost identical in size but very different in price.
When people think of diamonds, they refer to their weight in “carats ” Why, and where does that word even come from ? First, carat are a very accurate metric measurement, and the name has an interesting historical origination
One would probably have never guessed that the carat we derived from the carob seed, which comes from the locust tree. Coincidentally, the carob seed was a great benchmark for measuring diamonds and weight.
Jewellery merchants used them as counterweights in hand-held balance scales. Backthen, “one -carat” may have had a 12 point spread (by that I mean between 0.95 to 1.07 carats).
Luckily, according to GIA, this changed in the early twentieth century, when a “carat” was standardised worldwide to equal 200 milligrams, 1/5 of a gram, or 0.200 gram. This means that it would take approximately 142 diamonds to equal 1 ounce.
The Byzantine era used glass pebbles, based on carob seeds, for weighing coins, which weighed in at 196 mg, consistent with the average weight of an individual carob seed. However their use eventually diminished as it was discovered that despite their visual uniformity, the seeds were not actually consistent in weight. Many attempts were made to standardise the measurement of gemstone weight and it was only in 1907, at the Fourth General Conference on Weights and Measures that the “carat” was adopted as the official metric measurement for gemstone weights.
In 1913 the United States officially accepted the ‘carat’ as the gemstone measurement, and in 1914 the United Kingdom and Europe followed suit. By the 1930s, the majority of the diamond and gemstone industry had agreed to the standardised measurement, which is still in use today.