Along with your ornament, you will need a black stone similar to the jeweller's stone. Rub your piece of jewellery on the stone and add nitric acid to the mark. The acid will dissolve any other metals other than pure gold. If the mark dissolves upon applying nitrohydrochloric acid, it confirms the gold is pure.
Some of the most common methods used in the modern gold industry are the fire assay, X-ray fluorescence, and inductively coupled plasma mass spectrometry (or ICP-MS).
Fire and fluorescence
The fire assay is the traditional method used in the hallmarking industry (to certify gold in jewellery as 9 carat or 18 carat, for example), and also often used in gold mines to test the quality of ore.
Though complicated, fire assay is considered as the most reliable and accurate way to test the purity of gold. However, because of its destructive nature, it is usually used for large quantities or bullion.
Gently drop your gold item into the water. Real gold is a heavy metal and will not float, so if your gold item floats you know it is not real gold. Also, if you notice rust or tarnishing on the item after being in water, this is also a sign it is not real gold since gold doesn't rust or tarnish.
Pawn shops use various methods to test gold before pawning. One of the most widely used methods is the acid test, which involves applying nitric acid to the gold item to determine its purity. The magnet test is another simple method used to test if gold is real or not.
Purity: 24K signifies 99.9 % purity and 22K is approximately 91 percent pure gold, with the other 9% consisting of other metals such as copper, silver,zinc, etc. Durability: While 24K gold is brilliant in colour, the jewellery (if made) with 24K gold won't be as durable as 22K gold jewellery.
The purer the gold, the stronger the acid required to dissolve it. Measured strengths of nitric acid are used to test for 14k and lower. Aqua regia, a mixture of one part nitric acid and three parts hydrochloric acid, is used to test higher karat purity through the process of comparison and elimination.
Rub your gold against a jeweler's stone.
Position a black jeweler's stone on a table. Hold your gold piece firmly in your hand. Wipe it across the stone firmly enough to leave a mark. If the mark that you've left on the stone is solid and gold in color, then the piece is pure.
Hold a strong magnet next to a piece of gold and watch for a reaction. Gold is not magnetic, so there should not be any attraction to magnets. If there is, you most likely don't have real gold. However, some of the base metals that can be mixed with gold are also non-magnetic so you can get a false read.
Drop the gold into a jug of water to see if it sinks.
Real gold is a dense metal, so it falls directly to the bottom of the jug. Imitation gold is much lighter and floats. Real gold also doesn't rust or tarnish when wet, so if you see a discoloration, you probably have plated gold.
You will also need a small file or sandpaper to scratch the surface of the gold to be tested. To perform the test, first, scratch a small area of the gold with the file or sandpaper. This will remove the top layer of gold, exposing the inner layer. Next, apply a small drop of nitric acid to the scratched area.
First of all, the metals that might be mixed into a fake piece of gold or silver might be non-magnetic materials to begin with. For instance, a gold watch that is combined with traces of stainless steel will be undetectable in the magnet test, because stainless steel itself will not stick to the magnet.
It is possible that an 18k gold piece sticks to a magnet. 18k or 18 karat means that a specific alloy contains 75% of pure gold and 25% other metals. Since pure gold is not magnetic, gold itself will not be responsible for the magnetism, but the metal alloyed may be.
Check if your gold is real by performing the magnet test. Real gold will not attract a magnet. To test if 18k gold is real, hold it next to a magnet. If the magnet sticks to your jewelry, then it does not have a high percentage of gold but is made up of other, more magnetic metals.
Pure gold on its own cannot stick to a magnet. However, if you have an alloy of gold, then it could stick to a magnet. An example of a gold alloy that may stick to a magnet is gold with over 20% of its atoms replaced by iron. In very cold temperatures this alloy of gold may magnetize all on its own.
Neodymium magnets are very strong and can help to test the authenticity of gold and silver bars, coins, bullion, or jewelry.