The most trustworthy method to test if something is gold plated or solid gold is to have an acid test done it. For the acid test, take a small piece of jewelry, or using a small needle scratch a tiny part in your gold, take a dropper given in the acid kit, fill it with acid.
Fill a cup or bowl with water and carefully drop your gold piece into it. If the gold is real, it will sink to the bottom of the cup. If it's fake, it will float to the top or hover in the middle of the cup.
If your gold piece turns black or green when the vinegar is on it, or if it starts to smoke or fizzle at all when the vinegar touches it, it is most likely not real gold. If your gold piece does not change colors and does not fizzle or react to the vinegar in any way, it is probably real.
If it's real gold it will not stick to the magnet. (Fun fact: Real gold is not magnetic.) Fake gold, on the other hand, will stick to the magnet.
The Nitric Acid Test
Gold is a noble metal which means its resistant to corrosion, oxidation and acid. To perform this test, rub your gold on a black stone to leave a visible mark. Then apply nitric acid to the mark. The acid will dissolve any base metals that aren't real gold.
Acid test.
An acid test can reveal the karat of solid gold jewelry, but it can also show whether jewelry is solid gold or gold-plated. With an acid test, a small sample of the jewelry is removed and exposed to acid to induce a color change. The resulting colors indicate which type of metal the jewelry is made of.
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.
In their pure, natural forms, gold, silver, aluminum, copper, brass, and lead are not magnetic. This is because they are all weak metals. Adding iron or steel to these metals can make them stronger and magnetic. Gold is often used in coins, jewelry, electronics, dentistry, aerospace, and awards.
Gold is not a magnetic metal, so if it pulls towards, or sticks to the magnet, it's fake. However, just because it doesn't react to the magnet doesn't mean it is real, as non-magnetic metals are used in counterfeit pieces as well.
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.
Goldmeter - real gold detector on the App Store.
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.
Fool's gold is actually iron sulfide, a non-magnetic, inexpensive and abundant material that is a byproduct of petroleum production.
Gold does tarnish and scratch over time. To preserve the luster of your gold jewelry, avoid exposure to household bleach and other cleaning products, which will quickly cause gold to discolor and possibly disintegrate.
First off, if your "pure gold" is magnetic, then there is iron inside (or maybe nickel). In fact, this is one way to tell if jewelry is actually gold. If it's not attracted to a magnet then there is no iron - but it still might not be gold.
Q: Will any metal detector find gold? Yes. Most metal detectors are capable of finding gold but some will do a much better job than others. Since gold has rather low conductivity, metal detectors that use higher frequencies will spot gold better than low-frequency detectors.
If the piece is real gold, the stamp should bear a manufacturer's mark and a karat marking, such as 14K or 24K. Fake gold may bear a karat mark, but will not have a manufacturer's mark.
The apple cider vinegar gold test is a great choice if you want to test your jewelry at home, as it is readily available and easy to do. After all, real gold will not react when exposed to the acids in vinegar, toothpaste and more.