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How to Identify Pure 24 Karat Gold

Avoid gold scams that diminish the value of your investment portfolio by learning how to identify 24 karat gold. The best way to identify 24K gold is to get the opinion of a qualified, reputable appraiser.

The Pure Gold Stamp

Pure gold, fashioned into objects like coins, bars and jewelry, may bear the following stamps of authenticity on the face, back, underside or on a tag attached to the piece:

  • A stamp that reads "24K" or ".999."
  • The word "karat" may be spelled out rather than abbreviated.
  • A manufacturer's name.

Pure gold coins and bars are more likely to bear a ".999" stamp and the manufacturer's name, while pure gold jewelry is more likely bear a "24K" stamp and sometimes may bear the manufacturer's name. Oftentimes, however, pure gold collector's items -- and some gold jewelry and objects made in Asia -- don't bear any stamp at all.

The Acid Test

Fact: Pure gold is highly resistant to acid.

So, when an object bears no authenticity stamp, a gold acid test kit has the tools and acid solutions used to figure out its gold purity. You can buy a gold acid test kit from a silver, gold or gem tools dealer.

A gold acid test kit comes with:

  • Nitric acid, however, a very strong acid called aqua regia may be included in the kit to test 24K gold.
  • Specialized stone -- usually a piece of slate.
  • Gold needles.

Testing for pure gold usually goes as follows:

  1. Scratch the suspected pure gold item on the stone -- typically the underside of the piece where the scratch won't matter -- until it leaves residue.
  2. Scratch a 22K gold item on the stone next to the suspected pure gold residue, until it also leaves residue; some kits come with a 22K gold needle that you can use. Test results are based on comparing two types of gold -- one known and one unknown.
  3. Place a drop of acid -- the one provided in the kit for testing pure gold -- on the lines of residue and leave it for no more than 40 seconds, according to the Gemological Institute of America. The residue that remains, and does not corrode, is pure gold.

Warning

The lower the gold content in an item, the faster it corrodes when exposed to acid. So, if you use gold that's less than 22K gold to conduct a pure gold acid test, for example 14K gold, the most you'll find out is that your item is higher than 14K gold. That's why you want to use the highest karat gold you can get your hands on to conduct the pure gold comparison test.

Wear protective gear, work in a very well ventilated area and follow the kit manufacturer's instructions carefully -- which vary -- to test the purity of your gold object.

Other Gold Tests

  • Scratch test -- an item is scratched to see if the metal underneath the surface is gold;
  •  Magnet test -- when a magnet is used to see if it attracts an item. Gold is not magnetic.

These tests only tell you if an item has gold content, but they don't tell you if it is pure gold.

About the Author

Maya Black has been covering business, food, travel, cultural topics and decorating since 1992. She has bachelor's degree in art and a master's degree in cultural studies from University of Texas, a culinary arts certificate and a real estate license. Her articles appear in magazines such as Virginia Living and Albemarle.