What Is 18-Karat Gold? A Complete Guide to Gold in Jewelry
When looking for gold jewelry, you have probably seen terms such as 18k gold, 9k gold, 24k gold, or 750 milles. What does all this mean? Is higher karat gold better? Does 24-karat gold jewelry really exist? In this guide, we explain it all in simple terms.
What is a karat?
A karat is the unit of measurement that indicates the amount of gold in a piece of jewelry. It is calculated out of 24 parts—that is, a 24-karat piece of jewelry would be 100% gold, an 18-karat piece contains 18 parts of gold out of every 24, and a 9-karat piece contains 9 parts of gold out of every 24.
It is also expressed in milles—that is why you will find the 750 (18k gold) or 375 (9k gold) hallmark engraved on jewelry. That number indicates how many parts out of 1,000 are gold.
What is 18-karat gold?
18-karat gold—also called 18k gold or 750 gold—contains 75% gold and 25% other metals, generally copper and silver in different proportions. It is the most widely used jewelry standard in Spain and in countries with a Mediterranean jewelry tradition.
That 25% of other metals is not a defect—it is a necessity. 24-karat gold is too soft to make jewelry that can withstand daily wear. By combining it with copper and silver, a much stronger alloy is created that retains all the shine and value of gold. Furthermore, by varying the proportions of those metals, the different colors of gold are obtained:
- Yellow gold—the classic alloy with copper and silver
- White gold—palladium is added to achieve the silver tone
- Rose gold—a higher proportion of copper, which gives that very fashionable warm tone
In all three cases, the percentage of gold is exactly the same—75%. What changes is the composition of the remaining 25%.
And what about 9-karat gold?
9-karat gold—also called 375 gold—contains 37.5% gold and 62.5% other metals. It is the lowest karat legally recognized in Spain as fine gold, and it is especially popular in the United Kingdom and Northern Europe.
It has one very clear advantage: the price. Because it contains less gold, a 9k piece of jewelry can cost approximately half as much as the same piece in 18k. This makes it a very attractive option for those who want authentic gold jewelry without a large expense.
And here comes an important point that many people do not know: 9k gold does not lose its color over time. It is genuine fine gold throughout the entire piece—it is not plated, it is not goldfilled, and it does not have any coating on top. The color is part of the metal and does not wear off or peel. This radically distinguishes it from gold plating or goldfilled, where a very thin layer of gold covers a base metal that eventually shows with use.
At Pepe Lozano Joyeros, we work with both 18-karat gold and 9-karat gold, always with its corresponding authenticity hallmark and quality certificate. You can see our selection of 9k jewelry in our 9K Selection collection.
Plating, goldfilled, and fine gold—they are not the same
We take this opportunity to clarify a very common confusion. When you search for gold-colored jewelry online, you will find three very different types of products:
- 18k or 9k fine gold—genuine gold throughout the entire mass of the jewelry. The color never fades because it is the metal itself.
- Gold plating—a very thin layer of gold over a base metal, generally steel or brass. With use, that layer wears down and the base metal begins to show. It can last for months or a few years depending on the thickness of the plating.
- Goldfilled—similar to plating but with a somewhat thicker layer of gold. It lasts longer than plating, but it is still a surface layer that also wears down over time.
The difference in durability and value is enormous. A 9k fine gold piece of jewelry is for life—a plated piece, no.
Does 24-karat gold jewelry exist?
There is a very widespread belief here that is worth clarifying. Many people think that the highest quality jewelry is 24-karat—100% gold. The reality is that in Spain it is practically impossible to find 24k gold jewelry, and there is a very specific reason for this.
24-karat gold is too soft to make jewelry. It scratches easily, deforms with impacts, and does not withstand daily wear. That is why in Spain—and in most countries with a jewelry tradition—24k gold is reserved exclusively for investment bars and coins. If someone offers you a 24k gold piece of jewelry in Spain, be suspicious—either it is an incorrect statement, or it is a piece so soft that it will not serve to wear it.
The highest quality standard in Spanish jewelry is 18-karat gold—with that 75% gold that guarantees both the richness of the metal and the resistance necessary for a piece of jewelry that lasts a lifetime.
How do I know what karat my jewelry is?
Look for the hallmark engraved on the piece—it is mandatory by law in Spain. You will find the number 750 for 18k gold or 375 for 9k gold, engraved on the inside of the ring, on the clasp, or in a discreet place on the jewelry.
At Pepe Lozano Joyeros, all our gold jewelry carries its authenticity hallmark and is sent with a quality certificate, free and insured shipping throughout Spain, and 15 days for exchange or return.