Au on jewelry : meaning and origin

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If you buy jewelry, you may have seen indicators such as numbers or letters on it. These are important because they allow the informed observer to know the jewelry composition. But some annotations, such as Au on jewelry, remain mysterious.

What is Au on jewelry? What is its origin? What are the other indicators that complement it? We will answer all these questions in this article!

What does “Au“ mean on jewelry ?

"Au" is the chemical sign that represents gold on the periodic table of elements. It means that your Au jewelry is, fully or partially, made of gold. Other materials that make up jewelry are also present on the periodic table. For exemple, you can find "Ag" for silver and "Cu" for copper.

Why does “Au“ mean “gold” on jewelry ?

“Au” comes from the Latin “Aurum” which is the origin of the word "gold" in Latin languages such as French ("or"). We find this origin in the name of the rocks from which gold is extracted: gold-bearing rocks, also called auriferous rocks. Other Latin words derived from the lexical field of gold. This is the case of “aurora” (same in English, “aurore" in french), uro ("to shine" in English, “briller” in french) and australis ("southern" in English, “austral” in french).

However, note that the use of “Au” is uncommon in the jewelry world. In fact, jewelry fully made of gold is rare. The vast majority of gold jewelry is made of multiple materials. The “Au” indication does not indicate the percentage of gold present in the jewelry. Therefore, other indicators are used to complete this information.

Other indicators to precise gold composition of “Au” jewelry

Frequently used indicators are 2 or 3 digit numbers. The 2-digit numbers followed by the symbols "k" or "ct" represent carats while the 3-digit numbers represent the percentage of pure gold in the jewelry. These two indicators show the same information in two different ways. Thus, a piece of jewelry with the inscription "Au 18k" or "Au 750" has the same proportion of gold to its weight. It means that 750 part out of 1000 is gold. We detail the main indications that you can find on your gold jewelry:

The most frequently used indicators for "Au" jewelry

Au 10k gold (Au 416), Au 14k gold (Au 585) and Au 18k gold (Au 750) are the most common hallmarks you will find in a jewelry store or artisan. They contain 41.6%, 58.5% and 75% gold respectively. Note that Au 10k is the minimum standard you can find in the USA jewelry market. 18k gold could be considered as fine jewelry.

The most rarely used indicators for "Au" jewelry

Some gold marking are less common depending on the geographical area and time.

First, the most commonly used symbol for gold in the United States are not necessarily the same in other countries. So be careful to find out about the jewelry regulations in the countries where you operate. Here are two examples:

  • Au 10k (Au 416) is replaced by Au 9k (Au 416) in France.
  • Au 14k (Au 585) is replaced by Au 14k (Au 584) in Russia.

Note that several 525 jewelry have

have been found in the United States. Indeed, the "8" has changed into a "2" over time. Be aware that time may alter the information provided when the jewelry was created.

Second, the production of jewelry with the indications Au 12k (Au 500) and Au 15k (Au 625) is stopped for many years. They are indicating that the jewelry is composed of 50% and 62,5% of pure gold. They are therefore uncommon on the new market. You will find them more easily on the second hand market. It attests to the jewelry age.

Indicators used for the exceptional "Au" Jewelry

Exceptional Au jewelry sold for tens of thousands of dollars is mainly marked Au 22k (Au 916) or Au 24k (Au 999). They are respectively composed of 91.6% and 99.9% gold. These are fine jewelry pieces mainly produced in the Middle East and whose yellow color betrays their high gold composition. These gold marking are indicating that the jewelry, whatever it’s engagement ring, pendant necklace or au gold bracelet, is exceptional fashion accessory.

Note that it is important to check the composition of the au gold, especially if you are buying piece of jewelry on the second hand market. Don't be fooled by nice jewelry presentation in high end jewelry box. Indeed, despite what au mean on jewelry, it could have been "scraped" which could reduce its gold content. Gold ring, gold pendant and jewelry designs that you own may want less than the price you bought them for. Making sure your custom jewelry is not just gold plated is not a detail!

Checking gold composition of “Au jewelry”

Methods to check gold composition

There are three main methods to check the gold composition of Au Jewelry: with a nitric acid kit, with a spectrometer and by electrical measurement with a professional device, such as an M24. Today, we will only present the last one which is the most frequently used.

Electronic measurement to check gold composition

The M24 is a professional grade gold tester that is used in the vast majority of jewelers to test the composition of gold jewelry that is sold.

 Step #1: Turn on the RS Mizar M24 gold tester and make sure it works.

Step #2: Clean your jewelry to remove oxidation and impurities that could bias the result. Next, attach the alligator clip to a gold surface of your jewelry, other than the cleaned surface. Make sure it is not in contact with any other material such as a gemstone.

Step #3: Choose the button that matches the gold you are testing. Consider using the white gold button for silver colored jewelry and the yellow gold button for others.

Step #4: Add the test solution to the well of the gold tester. Expel the air from the bottle before closing it.

Step 5: Touch the cleaned area of the gold coin or platinum jewelry with the test solution in the well, hold it in place and wait for the "Test" light to come on.

Step 6: When the light goes out, the display will show you the carat number of your jewelry. This will allow you to determine if your gold ring or gold pendant is gold plated or not.


Au on jewelry mean that it contains gold. It comes from latin “Aurum”. But to know the gold content of your jewelry, you need the other indicators that are the 2 or 3 digit numbers. Electronic measurement is the only 100% safe option to determine how much gold is in your jewelry. Si Au is the gold symbol, ag is the sterling silver’s one. Ag silver means the jewelry contains sterling silver without specifying the quantity. You will also need to perform a test to determine the exact composition of your heart necklace and wedding band.

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