Fraudsters who make counterfeit gold have modern technology and skillfully make fakes that are close to the noble metal in density, color, and even chemical properties. Moreover, quite often a fake can be "partially real" - i.e. still contain a little gold, which provides the product with the appropriate chemical performance. However, there are ways to check if the real gold is in front of you or not.
You can try to identify gold "by ear". The sound when falling on the glass surface of the ring, in the authenticity of which you are sure, and the tested ring should be the same.
You can also draw a small line on a solid object with both pieces of jewelry. If both items leave a similar mark, there is a good chance that they both have the same fineness.
Try using a magnet. Precious metals do not attract. However, copper and aluminum do not magnetise either. Just in case, it is worthwhile to estimate the weight of the product, because aluminum and copper are much lighter than gold.
Apply a drop of iodine to the gold surface for 3-5 minutes. Then, gently wipe off the liquid. If the color of the metal remains the same, then in front of you, most likely, real gold.
Alternatively, try soaking the jewelry in vinegar. If it darkens, it is fake.