Place your jewelry on a table or hold it in your hand, pour some white vinegar on the metal directly (a dropper can also be used) if the metal of the jewelry changes its color, it is not pure gold and if it keeps shining then you have real gold in your hand.
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.
What to do: Hold the magnet up to the gold. 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.
Color of the gold
Pure gold is too malleable to be made into jewelry, so authentic gold chains do not have this bright countenance. Another thing is discoloration. Fake gold jewelry has a very thin layer of gold plated onto it. So if you see an inconsistent color of some part of the jewelry, it could be a fake.
Take a cup or glass, fill it up with water, now bring the gold that you want to test. Drop it into this filled glass. If the gold floats, it is surely not real but if the gold sinks to the end of the glass then it is pure gold. The real gold will sink due to being a heavy metal.
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.
Look for an official number marking on the gold.
It is usually visible on the surface of coins and bullion. The stamp is a number from 1 to 999 or 0K to 24K depending on what kind of grading system was used. Use a magnifying glass to help you identify the hallmark.
Drop a small amount of liquid nitric acid on that scratch and wait for a chemical reaction. Fake gold will immediately turn green where the acid is. Gold-over-sterling silver will become milky in appearance.
Goldmeter - real gold detector on the App Store.
A: When you clean jewelry with vinegar, you can submerge your gold jewelry in the vinegar solution for up to 20 minutes, but it's best not to go beyond that point. It is important to note that vinegar is an acid and can react with certain metals, causing discoloration or even damage to the metal.
Gold must be stamped with a hallmark that tells the purchaser what karat the gold is. 18- karat gold will have a small stamp on the inside of the jewelry that reads 18k.
eodymium magnets are very strong and can help to test the authenticity of gold and silver bars, coins, bullion, or jewelry.
Smell the Metal
While not a surefire way to distinguish between authentic and fake silver, you can perform an odor test by simply smelling the chain. Sterling silver is odorless, so if you detect a smell like sulfur or something metallic, you may want to verify the chain's composition with a trusted jeweler.
Markings There are several markings that indicate the gold quality of a chain. K, KP, KT markings will often include a number, such as 14K which indicates the chain's gold content. 10K is the minimum gold content to be considered a real gold chain. Other markings may include numbers like 583 or 585.
Scratch Test
If the metal doesn't change throughout the cut, the jewelry is more than likely solid gold. Gold plated jewelry will typically have a line of demarcation in the scratched area where the gold plating ends, and the base metal begins.
This is actually false. Toothpaste can damage your diamonds, gemstones, gold and silver. Toothpaste is abrasive and has a hardness of around 3/4 on the Mohs Scale of Hardness. Metals such as gold and silver are softer, so toothpaste can actually scratch damage your gold and silver jewellery.
In their pure forms, gold and silver happen to be very soft metals—soft enough that you should be able to mark them with your teeth. According to the Mohs hardness scale—which relates pairs of materials according to which one will scratch the other first—gold scores a 2.5 and silver, which is harder, a 2.7.
The Float Test
Place your gold piece into the water. If it's genuine gold, then it will immediately sink to the bottom of the cup. Pure gold is heavy due to its high density – 19.32 g/ ml. If your gold item floats or hovers above the cup's bottom – it's fake or plated gold.
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.