Part 2: Carats and Karats
Welcome to Part 2 of Carats and Karats.
Part 1 was all about carats! A quick refresh: carats are a unit of measurement for the weight of a gemstone. Each carat weights 0.200 g or 200 mg. Different gemstones can be the same size but have different carat weights.That is due to their relative density which is expressed through specific gravity.
Onto this week’s topic of karats and gold. The word karat is the measurement which indicates the purity of gold. In jewellery, pure gold is not always used. Pure gold is very soft. It could easily be deformed and have your precious gemstones slip out. How awful would it be, to look down at your hand and see that your ring is missing a stone… pretty awful in my opinion!
Due to this softness, gold for jewellery is most often mixed with other metals. This mixture is called an alloy. When you mix different metals together, the alloy will take on properties from all metals mixed together.
The number that is listed in front of karat, tell us how pure the gold is. One karat is 1/24 part of a gold alloy. Pure gold is 24 karats, which can be written as 24K to 24kt. All 24 parts are gold. However, 100% pure gold is unattainable, therefore, 99.95% is permitted in commerce. (Fineness on Wikipedia)
With nothing being completely straightforward and simple, there is also another way to express the purity or fineness of gold. Fineness describes the purity of gold in the parts per 1000. The purest gold achieved was by the Perth Mint in in 1957 which produced a ‘proof plate’ that was almost 999.999, also known as six nines. (Perth Mint) The Royal Canadian Mint regularly produces gold coins that have a five nines pureness or 999.99.
You can also check out their website here for their gold coins.
18kt gold is 18 parts pure gold with 6 parts being other metals. 18kt gold is 75% pure gold. 14kt gold is 14 parts pure gold and 10 parts other metals thus it is 58.3% pure gold. The higher the karat out of 24, the purer the gold.
Now different countries will have different standards for what alloys can be considered gold. In Canada, the minimum standard is 9kt or higher according to the Competition Bureau. 9kt is also the minimum standard for gold in the UK according to the Assay Office of Great Britain. In the United States, the minimum standard is 10kt account the World Gold Council. I was not able to find any minimum standards for Qatar. If anyone knows them or where I can find them, reach out, I would love to know!
Depending on the country you are in, you may hear your local jeweller say that a bracelet has a fineness of 750. You may also see a stamp on your jewellery that doesn’t have 18kt gold but 750 or 0.75. They all indicate the same thing that your gold is 3/4 pure gold with 1/4 other metals.
We know that pure gold is a bright yellow colour but how do we get rose gold or white gold? Great question. An alloy is also how we are able to have different colours of gold. A rose gold alloy is comprised of yellow gold as well as copper and a small percentage of silver. Depending on how much copper will determine the colour. The more copper the pinker the gold. 14kt rose gold is more pink than 18kt rose gold.
White gold is also an alloy. Pure gold can be mixed with such metals as silver and palladium. These metals will give it the white colour. There is also one other step that white gold involves and that is rhodium plating. This gives the alloy a very nice lustrous white colour. The plating needs to be done every few years. As you can see these rings on the left need to be plated quite badly as its has been 3.5 years. Yes, these rings are mine and yes, I will be getting them done soon!
Now time to dive down the rabbit hole of the carat, karat etymology. How did these two words end up meaning what they do? According to Merriam-Webster dictionary,
“the name carat derives, via Medieval French and Italian, from Arabic qīrāṭ, meaning “bean pod” which is itself from Greek keration, referring to both the carob bean and small weight”
Since qīrāṭ is clearly not written in Arabic, here it is in Arabic: قيراط
Ok, so that explains how it relates to gemstone but what about the purity of gold? So in the late Roman Empire, there was a gold coin called the solidus introduced by Constantine in the 4th Century. (Merriam-Webster) The solidus weighed 24 carob seeds. Hence 24 karat gold or ذهب عيار ٢٤ قيراط.
The carob tree is found throughout the Middle East and the Mediterranean. Have you seen it in Doha at all? From what I can tell, they are at Aspire Park.
I love how this one word combines so many languages and cultures. French, Italian, Greek and Arabic. All countries that have rich histories with gems and jewellery.
And with that, this ends our discussion on carats and karats. I hope you enjoyed this series. Up next is a gem that is connected to an octopus. Any guesses?