I recently had a query via the contact form on our website about the meaning of this mark on a piece of jewelry: “CRP 10K”. Does that mean the item is gold plated or 10 karat gold? The answer is at the end of this article …
First, a little history. The karat marking of gold jewelry is somewhat like the English system of weights and measures compared to the metric system. (Except in England they write it “carats”. In the United States, we use “carats” for gemstones). Karat weights are based on the idea that pure gold is 24 karat. But pure gold is too soft to use in most types of jewelry, and of course it is 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 break, scratch deeply, or bend easily.
To indicate the ratio of gold to alloys, the karat system was developed. Since 24 karat, abbreviated 24K, is 99.9% pure gold (realistically it can’t be 100%), one karat is 1/24 pure gold. But a one carat gold ring would only have 4.2% gold! Therefore, you will find that the gold used in jewelry is generally alloyed from about 10K, which is 10/24 gold, or 41.7% gold, to 22K gold, which would be 91.7% gold. Sometimes an item can be sealed “14KP“, where the letter” P “stands for” leaded gold “, just another way of saying that the item is not made up of anything other than 14K 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 with “fineness”, which is simply 100 times the percentage of gold content without the percentage mark. So 14K gold is 14/24 = 58.3% gold, but the fineness is 583, or often marked 585. 24K, by the way, has a fineness of 999. Countries other than the US have different standards for what can be called “gold”: in France and Italy, the item must be at least 18K, but in Germany, it is only 8K! Fineness also applies to other jewelry metals such as platinum and silver.
So what about items that are not “solid gold”? That terminology is a bit confusing: “solid gold” could mean “unalloyed gold,” that is, 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 United States, a seller cannot use the term “solid gold” unless the item is 24K 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 articles, this makes a lot of sense; For example, a gold locket is very expensive if it is “solid gold”, which is why you often see gold-plated locket. However, gold plating is not good when used on a highly worn jewelry item, such as a ring. Depending on the thickness, the plating can wear off 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 electric current, called “gold electroplating”, and is marked “GEP” (since the applied layer is pure gold, it could be said to be “24K gold plated” ). Gold plating must be, by US law, at least 7 thousandths of an inch thick (one “thousand” is one millionth of an inch). If it is less than that, the item is said to have “gold sparkles” or “gold panning”. Gold can also be applied in a thicker layer than electroplating by mechanically bonding the gold to the base metal; The item is then said to be “gold filled”, marked “GF”. The US legal requirement for GF is at least 10K gold, which constitutes 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 were of higher quality, it 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, as “1/40 14K RGP”, which would indicate that 1/40 of the weight of the piece is composed of 14K gold.
Lastly, I should point out that it is common for gold-plated jewelry items (either electrically or mechanically) to be made of sterling silver. This result is called “vermeil”, pronounced “vehr-may”, and requires the plating to be at least 120 thousandths of an inch of 24k gold. But not all gold-plated silver is vermeil. Of course, it is possible to galvanize silver and simply mark it as “GEP”, which would only require a 7 mil layer of gold! So please read those magazine ads carefully when they talk about “24K Gold Plated Sterling Silver”.
So, let’s go back to the example. Within “CRP 10K”, only the “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.