I recently had a query through our website contact form about the meaning of this mark on a piece of jewelry: “CRP 10K”. Does that mean the item is gold plated or 10k gold? The answer is at the end of this article….

First, a little history. The karat mark on gold jewelry is somewhat like the English system of weights and measures compared to the metric system. (Except in England, they spell it “carat.” In the US, we use “carat” for gemstones.) Carat weights are based on the idea that pure gold is 24 karat. But pure gold is too soft for most types of jewelry, and of course it’s also very valuable. Therefore, gold is almost always mixed or alloyed with other less valuable but stronger metals to give it more strength. Otherwise, a pure gold ring would be easily broken, deeply scratched or bent.

To indicate the ratio of gold to alloys, the karat system was developed. Since 24 karat, 24K for short, is 99.9% pure gold (realistically it can’t be 100%), one karat is 1/24 pure gold. But a one karat gold ring would only have 4.2% gold! So you’ll find that gold used in jewelry is usually alloyed from around 10 karat, which is 10/24 gold, or 41.7% gold, to 22 karat, which would be 91.7% gold. . Sometimes an item may be stamped”14KP“, where the letter “P” stands for “lead gold”, just another way of saying that the item is not made of anything other than 14 karat gold.

In the United States, an item must be at least 10K to be called “gold” jewelry, and typical markings are 10K, 14K, 18K, and 22K. Items made in other countries are often marked “fineness”, which is simply 100 times the percentage of gold content without the percentage mark. So 14 karat gold is 14/24 = 58.3% gold, but the fineness is 583, or is often marked as 585. By the way, 24 karat gold is 999 fine. Non-US have different standards for what can be called “gold”: in France and Italy, the item must be at least 18 carats, but in Germany, only 8 carats! Fineness also applies to other jewelry metals such as platinum and silver.

So what about items that aren’t “solid gold”? That terminology is a bit confusing: “solid gold” could mean “unalloyed gold”, i.e. a fineness of 999. Or it could mean “made of gold and not hollow or plated”. For the purposes of our discussion here, we will use the latter meaning, although in the US, a seller may not use the term “solid gold” unless the item is 24-karat solid gold.

Gold is often applied to a cheaper (and stronger) metal, such as brass or copper, to make a much less expensive piece of jewelry. For some large items, this makes a lot of sense; for example, a gold locket is very expensive if it is “solid gold”, which is why gold plated lockets are often seen. However, gold plating is not good when used in a jewelry item that is worn a lot, such as a ring. Depending on the thickness, the coating can wear away in a matter of weeks on such an item, quickly exposing the base metal. and creating tarnish and corrosion.

Gold can be applied to an item using an electrical current, called “gold electroplating,” and is marked “GEP” (since the applied layer is pure gold, it could be said to be “24-karat gold plated”). “). Gold plating must be, by US law, at least 7 thousandths of an inch thick (“one thousandth” is one millionth of an inch). If it is less than that, the item is said to be “gold flashed” or “gold washed”. Gold can also be applied in a thicker layer than electroplating by mechanically bonding the gold to the base metal; then the item is said to be “gold filled”, marked “GF”. The US legal requirement for GF is at least 10K gold, which makes up at least 1/20, or 5%, of the item’s weight. This would mean that the item would be marked as “10KGF”, but if the gold was of a higher quality, you would see “18KGF”, for example. A similar process is gold plate, marked “GP”, or rolled gold plate, marked “RGP”. This process would specify the percentage of gold, as well as the quality, in the stamping, such as “1/40 14K RGP”, which would indicate that 1/40 of the weight of the piece is made up of 14K gold.

Lastly, I should point out that it is common to gold plated (either electrically or mechanically) jewelry items made from sterling silver. This result is called “vermeil,” pronounced “vehr-may,” and requires that the plating be at least 120 thousandths of an inch of 24-karat gold. But not all gold-plated silver is vermeil. Of course, it is possible to electroplate silver and simply mark it “GEP”, which would only require a 7 mil gold layer! So read those magazine ads carefully when they talk about “24k gold plated sterling silver”.

So, back to the example. Within “CRP 10K”, only “10K” fits any legal mark, so we can assume that if the item is legally marked, it is made of “solid” 10K gold. The “CRP” does not fit any of the standard markings, so it is probably an abbreviation for the jewelry manufacturer.