Testing For Precious Metals: How to Use Common Testing Methods to Determine Authenticity & Purity

When determining a value for items made of precious metals, it is key to know what type of metal you are valuing. First, we must determine whether the piece in question is costume, made of base metal, or precious. To determine if a piece is made of base metals or precious, there are a few testing methods we can employ. The first step is the Smell Test. Precious metals will have little to no smell or a very faint sweet smell. Base metals will have a metallic smell. Think of holding a bunch of old keys or change in your hand and the way it makes your hands smell. If the smell is not noticeable, the next test will allow you with confidence, to say either, “This piece is costume” or “This piece is made with precious metals”. A magnet test is going to tell you right away if a metal is precious or base. Precious metals such as Gold, Silver, Platinum or Palladium will NOT be magnetic and a magnet will NOT have any pull on the item. Base metals will almost immediately be pulled to the magnet.

          Testing Methods     

Acid Testing Metals

Using Acid to test precious metals is the most definitive method for testing jewelry. When testing precious metals, we are looking for a chemical reaction between the metal on the slate and the acid. The reaction we are looking for is the Oxidization of the metal. Silver will oxidize and turn a rust-red color when wiped off the slate. Gold will be slowly dissolved based on the purity. Begin by scraping the metal on the slate slab to create a clear, defined line. Visually inspect the line – does it look off-color from the original piece? If so, the piece is more than likely plated or simply not precious. When testing Sterling, drop a drop or two of the Sterling Silver acid on the line. Allow the acid to react with the metal in question for about 10-20 seconds.

Acid Testing Metals        Acid Testing Marks

You can get an initial idea by looking at the drop on the slate – if the drop starts to turn a blood-red color, you most likely have silver. To more definitively determine, wipe the acid and line away with a paper towel. Examine your paper towel – Is there a rust-red line? If Yes, then Silver is present If no, and the line is a bluish-green color, then there is no silver present.

Acid Testing Gold

When testing for gold, follow the same steps in testing Sterling. Begin by Scraping the piece on the slate and visually examining the line. For gold, make a slightly longer line or make a series of lines. Gold Acids come in varying degrees of acidity depending on what type of gold you are testing for.

Gold Acid Levels

10K, 14K, 18K, 22K

When testing for 14K gold, first use the 10K Acid. If the acid fully and quickly dissolves the line, you do NOT have gold. You more than likely have a counterfeit or faux item. If the acid does NOT dissolve the line, move up to the next highest acid, 14K. 14K acid will dissolve 10K, 18K acid will dissolve 14K, etc.