The term "carat" is often a source of confusion because it does not mean the same thing depending on whether we are talking about gold or precious stones.
On one hand, it signifies the purity of gold , on the other it signifies the weight of the stone .
I will explain simply how to understand the difference and learn to use each measurement.
The carat of gold
When it comes to gold, the carat (also written "K", "kt") expresses the proportion of pure gold contained in the alloy.
Pure gold corresponds to 24 carats , you cannot go higher.
Here are the most common carats:
24 karats = 100% pure gold
18 karats (also called 750/1000) = 75% pure gold
14 karats (also called 585/1000) = 58.5% pure gold
9 carats (also called 375/1000) = 37.5% pure gold
Pure gold (24K), being too malleable , is rarely used alone for the manufacture of jewelry intended to be worn daily.
In high-end jewelry, 18-carat gold is generally preferred , as it offers an ideal balance between purity, strength, and durability.
This alloy also allows for the creation of the color variations you all know: rose gold, white gold, and red gold. This color difference is possible thanks to the remaining 25%. Depending on the metals chosen, the alloy changes color.
For example, in rose gold, the remaining 25% is composed of 20% copper and 5% silver.
The carat weight of precious stones
When it comes to precious stones, the carat (also written "ct") indicates the weight of the stone.
This unit of measurement applies to diamonds as well as all other gemstones.
1 carat = 0.20 grams
For example :
- 0.50 ct = 0.10 gram
- 1 ct = 0.20 grams
- 2 ct = 0.40 grams
The greater the weight, the rarer the stone, and the more its price can increase exponentially.
A stone twice as big is not twice as expensive.
In summary
The carat of gold indicates the percentage of pure gold in an alloy, while the carat of a gemstone indicates its weight.
These are two very distinct units of measurement to know, especially since they are both used in the same field!