If you’re thinking of purchasing or having a piece of gold jewelry made, deciding whether to use 9-karat or 18-karat gold can be a difficult decision. Each type of gold has positives and negatives, so it’s a good idea to consider all of the factors before choosing the gold type that suits you best.
Gold Content
The biggest difference between 9 karat and 18 karat gold is how much gold is in the metal alloy. Gold is an extremely soft metal. It’s not very durable, so it’s rarely used in its pure form because it can’t stand up to daily wear and tear, even when the wearer is very careful with it.
Instead, gold is mixed with other metals, such as silver and copper, to give it added strength. These other metals can also change the color of the gold, which is how rose and white gold are made.
Gold that is 18 karat contains 75% pure gold, and the rest of the alloy is made up of other metals. Nine karat gold is only 37.5% pure gold and 62.5% other metals.
The numbers 9 and 18 are derived from how many karats of pure gold are found in 24 parts. For example, there are 9 parts or karats of pure gold in 24 parts of the alloy.
Color
Because it contains less actual gold, 9 karat gold is not quite as vibrantly colored as 18 karat gold. This is particularly noticeable with yellow gold, but the color difference is often less noticeable if the jewelry piece is white or rose gold.
Nine karat gold is sometimes less lustrous than 18 karat gold as well. Overall, the color of 9 karat gold will be paler than that of 18 karat gold.
Value
Eighteen karat gold contains twice the amount of pure gold that 9 karat gold has, so it is worth twice as much. The price of gold fluctuates frequently, and it can even change hour to hour depending on the market and demand.
However, the cost for 18 karat gold is usually around $35 to $45 per gram. The price for 9 karat gold, therefore, would be between $17.50 and $22.50 per gram.
Hardness and Durability
Pure gold is very soft, so it stands to reason that the more gold is in a metal alloy, the softer that alloy will be. For this reason, 18 karat gold is quite a bit softer than 9 karat gold. Jewelry that is made with 9 karat gold is harder and will stand up better to dings and scratches.
However, the composition of 9 karat gold often makes it brittle. If it’s knocked around during normal daily wear, it can develop small chips and dents. These dents can be extremely hard to see, but over time, they’ll wear down the integrity of the piece.
Many jewelry pieces made with 9 karat gold, particularly rings, only last for one lifetime, and they may eventually snap or come apart.
Use
For jewelry with a more neutral, rugged appearance, 9 karat gold is often the best choice. It’s less expensive, will hold up well to daily wear, and won’t show visible scratches or dents. Any patterns or designs are also less likely to be rubbed smooth.
However, if you want a piece that will last for generations, 18 karat gold is generally a better option. Although the piece may display some wear and any design will be rubbed down over time, the piece is unlikely to break in any significant way.
Eighteen karat gold is also usually better for intricate designs, as it is much easier to shape due to its less brittle nature.
Markings
Most gold is marked along a hidden section of the piece of jewelry. For rings, the markings, which are called hallmarks, are usually found on the inside of the band. These markings tell jewelers and anyone looking to purchase the piece where it was made, who made it, and what type of gold was used.
Nine karat gold is marked with either a 9K, 9Kt, or 375 marking. The 375 indicates 37.5, the percentage of gold in the piece. Eighteen karat gold is marked with an 18K, 18Kt, or 750 stamp.
The 375 and 750 markings will be found in a hexagon shape, indicating that the metal is gold. Occasionally, pieces will have either a 9K P or 18K P mark. The mark stands for plumb and tells jewelers that the metal contains 9 or 18 karats of pure gold per 24 parts.
Not all gold pieces are marked. In the United States, gold jewelry does not have to be stamped, but when it’s sold, the gold karat count must be marked somewhere near the piece, such as on the packaging or a price tag.
Gold jewelry made in other countries might also be lacking a hallmark because those countries do not require one. A skilled jeweler can help you test unmarked gold to find out how pure it is.