How to Determine Whether Gold Is Real

• Place the gold in a jug of water and observe if it sinks: Get a container that can accommodate both the water and the gold you want to analyze. The temperature of the water does not really important, so lukewarm water is OK. Because real gold is a dense metal, it falls to the bottom of the jug. Imitation gold is significantly lighter and floats. "Real gold does not rust or tarnish when wet, therefore if you see discoloration, you are most likely dealing with plated gold."

• Put a few drops of vinegar on the gold: Place your jewelry or gold item on a flat surface. Apply some vinegar with an eyedropper and let it for around 15 minutes. Real gold does not change the hue, but counterfeit gold does. "You can alternatively soak the gold in vinegar for 15 minutes in a glass jar. This procedure is a little riskier because vinegar can destroy semi-precious stones on gold jewelry."

• Take note of any skin discolorations caused by wearing or holding the gold: Because pure gold does not react with sweat or oil from your skin, any black or green stains you see are caused by other metals. Silver leaves are hidden behind black marks, and copper leaves are hidden behind green marks. If you have a lot of these marks on your skin, your gold may not be as pure as you think. "Remember that the majority of gold goods are alloys of gold and other metals. Even 14K gold jewelry, which contains 58.3% gold, can leave these markings. Use further tests to guarantee the authenticity of your gold."

Reference
https://www.wikihow.com/Tell-if-Gold-Is-Real