A species of tree known as the carob grows in the coastal areas of Mediterranean Sea (e.g. in Egypt, Libya, Tunisia, France, and Spain). It reaches a height of about 15 meters and bears about 30 centimeter- long ponds. Each pod contains five to fifteen seeds which are flat and hard like tamarind seeds. These seeds of carob tree are known as carat. Fifty percent of these seeds is sugar, so in the time of drought when food is scarce, poor people in North Africa eat these seeds in order to survive.

Years ago, the jewelers of Europe used carob seeds as tiny weights for weighing diamonds due to the near uniformity in the weight of these seeds. The difference between weights of any two carob seeds is not more than two to five milligrams. (1 milligram = 0.001 gram). One carob seed weighs about 0.2 gram so it requires 5000 carats against one kilogram weight to balance the pans of scale. Nowadays, carob seeds are not used to weigh diamonds, but the jewelers still use the word ‘carat’ to measure the weight of their diamonds. According to an international agreement made in 1913, diamonds are weighed against a tiny weight of 200 milligrams, i.e. 0.2 grams.

On the other hand, the scale indicating the purity of gold is also called carat. When no other metal or impurity is mixed in gold, it is considered to be 24 carat or a 100 percent gold. In 18 carat gold, the remaining 6 carats equivalent (24- 18=6 i.e. 25%) comprises some other metal or alloy mixed with the gold. If you want to make jewelry out of your gold it would need to be mixed with other metals and alloys, else it won’t e hard enough to withstand the molding or the setting of stones inside.

## Measuring Diamonds

One diamond carat is around 200 milligrams. However, diamonds are also measured in points, which is about a hundredth of a carat. This means that one point is about 2 milligrams or 0.002 grams.

If we want to measure a diamond in carats and points, we first have to weight it in terms of milligrams or grams. We can then express the weight in carats and points. The following steps will come in handy:

1. Weighing the diamonds with a sensitive scale that can measure in milligrams. Make sure the stone is loose when it’s on the scale.

2. Recording the weight of the diamond in terms of milligrams (or ounces, if you prefer). The display on the scale should be steady. If it shows the weight in grams, multiply the number by 1000 and write it down.

3. Calculate the carats in the diamond by dividing the milligrams weight by 200. For instance, a diamond weighing 273 milligrams will be around 1.365 carats.

4. Once you have the diamond’s weight in carats, you can determine its points as well. For that you’ll simply multiply the number of carats by 100, as one carat is equal to 100 points. A diamond weighing 1.365 carats will be around 136.5 points.

5. You can also express the weight of a diamond in both carats and points. In the example above, the diamond can be said to be 1 carat and 36.5 points.

6. It’s also possible to calculate a diamond’s weight in terms of milligrams if you already know their measurement in points and carats. We can do this by first dividing the diamond’s points by 100 and adding that the to the number of whole carats in the stone.

7. If the weight of a diamond is 2 carats and 63 points, we ca7n divide 63 by 100 and add the result to 2. Here, 0.63 plus 2 equal 2.63.

8. We will then multiply 2.63 by 200 to get the diamond’s weight in terms of milligrams. This is equal to 526 milligrams, which is around 0.526 grams.

## Additional reading:

- Carat (mass) (Wikipedia)
- Carat (purity) (Wikipedia)