When we mention the word ‘carat’, a high percentage of those who hear it are likely to immediately associate it with diamonds or other precious stones. However, the carat was originally a unit of measurement for gold and is still used to refer to the purity of this metal. In this post we are going to explain where the term comes from and how many carats gold has according to its purity.
Since time immemorial, the value of gold has been related to its purity. It seems logical that two pieces of gold of the same weight do not have the same value, if in one of them the gold is mixed with another metal and in the other it is pure.
For this reason, it became necessary from the beginning of its use as a means of payment to establish a way of evaluating the purity of the gold pieces that were used as coins. We are talking about transactions carried out many centuries ago.
Gold as a means of payment
As explained by the Australian Perth Mint , one of the world’s leading mints (which mints bullion like the Kangaroo or the Koala ), the physical properties of gold, such as its durability, density and brightness, had made it the natural choice as a store of value even before it began to be used as a means of payment.
Indeed, about 2,000 years before the first coins were minted, a great innovation that appeared around 700 BC. C. (see image), gold was already used as a means of payment. The problem was that, in each transaction, the purity of the metal had to be proven and weighed on a scale to determine its exact weight.
The need to verify the purity of gold forced the creation of a specific system for this purpose, a system that has been maintained throughout the centuries and was later extended to precious stones as well.
The carat, unit of measurement
The system that was established then to measure the purity of gold and that has survived to this day, is based on a unit of measurement: the carat.
The etymological origin of ‘carat’ is in the Greek word ‘keration’, which passed into Arabic as ‘qīrāṭ’ and, from there. Designates the carob (whose scientific name is Ceratonia siliqua). Its relationship with gold is given because the seeds of this fruit were used as a standard to weigh gold.
This is because they are very regular seeds (they are all exactly the same), weighing a fifth of a gram, so they were considered very appropriate to serve as a reference in terms of the weight of gold and precious stones.
Hence, the carat was established as a measure of weight for gold. Each carat equaled 0.199 grams.
From carat to troy ounce
Over the centuries, the units of measurement were perfected and gold began to be weighed in a new measure that became the standard for many years: the grain (‘grain’ in English).
Each grain weighed 0.064 grams. For larger quantities it became necessary to acquire new units of measure. Thus, the so-called troy ounce was established, which took its name from the French city of Troyes, in whose important medieval market it began to be used.
This new measurement was equivalent to 480 grains or, what is the same, 31.10 grams . Do not confuse the troy ounce , intended to measure precious metals, with the conventional ounce or ‘avoirdupois’ , which is equivalent to 28.35 grams , and which is used in Anglo-Saxon countries as a unit of weight for any material.
The coexistence of the grain and the troy ounce forced the adoption of the custom of expressing the weight in grains and the price in troy ounces.
Carats of purity
At present, the carat has remained as the unit of measurement of the purity of gold. In an alloy that contains gold along with other metals, one carat is equal to 1/24 of pure gold . That is to say, that pure gold, without mixing with any other metal, would have 24 carats (24/24).
Pure gold, 24 carats (99.99% gold) , is used to mint investment coins and to make bars. It is soft, highly malleable and resistant to rust and corrosion, making it ideal for investment gold, which remains stored for years in vaults.
On the other hand, it is not usual for it to be used in jewelry, since being pure gold, it is more expensive and also, gold is a soft metal that has to be alloyed with others to increase its resistance to wear.
22 – carat gold (91.67% gold) is more resistant, when mixed with other metals such as silver or copper. It can be used in jewelry and also for minting investment coins.
In fact, the first bullion in history, the South African Krugerrand , is minted in 22-carat gold, mixed with copper, which gives it its characteristic reddish glow.
British gold sovereigns are also minted in 22-carat gold, as are unadorned gold jewelery such as wedding bands, chains or bracelets.
However, in jewelry, the most common is to use 18-carat gold (75% gold) , which reduces the price of the pieces and increases their resistance to wear, allowing filigree and intricate designs to be made that, if the piece were made of pure gold, they would not withstand daily use.