Gold Purity Levels Every Jewelry Lover Should Know

　Contents

• What is gold purity?
• Why is it expressed in 24ths?
• Differences based on gold purity
• Reasons for mixing other metals
• Summary

■What is gold purity?

Gold purity is an indicator that shows how much gold (pure gold) is contained in a gold product. It is generally expressed as "18 karat," "K18," or "18K." "K" is an abbreviation for karat, which is the initial letter of the unit that expresses the purity of gold contained in a gold product in 24ths.

■Why is it expressed in 24ths?

There are various theories, but according to one, gold is expressed in 24ths based on a tradition from ancient Egypt. Gold has been treated as a precious metal since ancient times, and it was considered an extremely valuable metal even then. In ancient Egypt, a method of dividing one weight into 24 equal parts was used to express the purity of gold-containing alloys.

This 24th system is related to the Egyptian sun worship. Egyptians highly revered the sun and considered a day of the sun to be 24 hours (100 in current terms). Derived from this idea, the purity of gold came to be expressed in 24ths.

Therefore, if 24 karat gold is replaced simply, it means "gold that is almost 100% pure," or ※pure gold.
(Pure gold: gold with a purity of 99.9% or higher)

As an aside, it is well known that gold was used in Tutankhamun, which you must have heard of. It is said that 23 karat gold was used for Tutankhamun. The reason why the entire mask was not made of 24 karat pure gold but rather had its purity lowered to 23 karat is said to be to obtain strength as a mask.

■Differences based on gold purity

Readers of this article must understand that "24 karat gold is pure gold, 18 karat is the next most expensive, and the lower the number, the cheaper it is."
However, some of you may not know how gold purity is calculated.
First, before explaining the differences based on gold purity, I will briefly explain how to calculate gold purity. It's very simple, so please try to remember it ◯

 
◯◯K ÷ 24K × 100 =〇〇%
*Considering 24K as pure gold

・In the case of 18K
　18K ÷ 24K × 100 =75%.

How was it? It was very easy to calculate the purity of gold.
From the example of 18K, we understood that 75% is pure gold.
In this way, gold purity can be easily calculated.

Now let's look at how gold purity differs.

【10K】
Gold purity is 41.7%, and the remaining 58.3% consists of other metals.
The advantage of K10 is that it is relatively inexpensive and easy to obtain. For example, K10 jewelry is suitable for everyday use, including casual settings. Therefore, you can enjoy it as daily accessories or fashion jewelry.

【14K】
Gold purity is 58.3%, and the proportion of other metals is 41.7%. K14 jewelry may not be widely used in Japan. However, it is used by many overseas jewelry brands.
The advantage of K14 is that it has a higher gold content compared to K10, so you can enjoy a more authentic gold shine and color. Also, K14 is relatively durable and resistant to scratches. It is ideal for jewelry that is often worn daily, such as wedding rings, necklaces, and bracelets.

【18K】
Gold purity is 75%, and the proportion of other metals is 25%. K18 is a purity used for high-end jewelry, including fine jewelry, and combines elegance and luxury.
The advantage of K18 is that it has a higher gold content compared to other purities, so it has a richer golden shine. Also, K18 jewelry is highly durable and guaranteed to be of good quality. It is a perfect item for special occasions such as weddings and formal events.

【24K】
Gold purity is 99.9%, which is almost pure gold.
Therefore, K24 jewelry has the highest quality and shine, and possesses high value. On the other hand, pure gold has the disadvantage of being very soft, which means it has low durability as jewelry and is prone to scratches. For this reason, it is not often used as general jewelry.

■Reasons for mixing other metals

I will explain the reasons for mixing gold with other metals in jewelry from three perspectives.

1. Improved Hardness and Durability
   I mentioned that pure gold is very soft. Therefore, pure gold alone would result in low durability for jewelry and products, making them prone to scratches and deformation. By alloying with other metals (mainly silver and copper), the hardness and durability of gold can be improved.
   
   
2. Color Change and Design Variety
   Pure gold has a yellow hue, but alloying with other metals changes its color tone. For example, adding silver or nickel creates a white hue, which becomes known as white gold. Also, adding copper creates a reddish hue, which is used as rose gold. In this way, various colors of jewelry can be created by combining gold with other metals, offering design versatility.
   
   
3. Economic Reasons
   Pure gold is an expensive precious metal and has a high price. On the other hand, other metals are relatively inexpensive. By mixing gold with other metals, the charm and value of gold can be brought out while keeping costs down. This allows more people to enjoy gold jewelry at affordable prices.