The purity hallmark – the most important clue about your item's value. The purity hallmark can be either in millesimal fineness or Karat system as mentioned above. For example, if you own the purest gold, you should see hallmark “999” or “24K” engravings somewhere on the item.
Pure gold is notated as 24K – this is the highest karat level for gold meaning it is 100% pure gold. 18K gold is 75% purity level, 14K is 58.3% purity level, and 10K is 41.7% purity level. As you can see, the higher the karat number, the more pure gold comprises the metal.
Vinegar is very destructive, so when you apply the vinegar to a fake piece of gold, the vinegar will cause the jewelry to tarnish. Gold is a non-reactive metal, so real pieces of gold will not react to vinegar.
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.
10k gold is the lowest solid gold alloy used for jewelry. It's composed of 41.7% gold and 58.3% alloy. Appearance: 10k gold is pale yellow in color. It's the least yellow of all the karat types since it contains the least amount of gold.
Pure gold (the highest karat 24k) will not tarnish because it is a noble metal, meaning it is resistant to oxidation and corrosion.
Scratch test.
If you cut deep enough that you expose underlying metal, you can assume that it is plated. If it appears to be made of a uniform composition throughout, then it is probably solid 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. If that necklace leaps to the magnet, your significant other has some explaining to do.
Yellow gold
As we know pure gold (24k or . 999) is yellow, but it is also very soft and unsuitable for making delicate jewellery. Also the higher the gold purity, the more expensive the metal is. In order to make a more durable metal, and also to reduce cost, we add an alloy to the pure gold.
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.
Goldmeter - real gold detector on the App Store.
The simple answer is that 24-karat gold is the only type of gold that doesn't tarnish. This is the most traditional form of gold, and it is what primarily comes to people's minds when they think of "gold." 24-karat gold is also the priciest type because it does not contain any other mixed metals.
Consider Rarity & Value
The Saint-Gaudens Double Eagle is considered one of the cheapest gold coins you can purchase, given its overall value. This is a U.S. coin that was minted between 1907 and 1933. It's universally recognized and noted for offering significant value beyond its face value because of its rarity.
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.
By law, gold jewelry sold by a vendor must have a stamp of the piece's purity, so finding a stamp is a good sign! If you can't find a stamp, it's possible it wore off with time, or was sold before the law was passed. Don't worry if there is no stamp to be found, you can always consult an expert!
Gold is not a magnetic metal, so if they pull towards the magnet, the beads are fake. However, if they don't react to the magnet, it doesn't necessarily mean they are real, as non-magnetic metals are used in counterfeit pieces as well.