Hallmark or Stamp: Look for a hallmark or stamp on the jewelry. Genuine gold jewelry will often have a hallmark indicating its purity, such as "18K" or "750" for 18 karat gold, "14K" for 14 karat gold, or "585" for 14 karat gold. If there's no stamp, it doesn't necessarily mean the piece isn't gold, but it's a good indication if there is one.
Magnet Test: Gold is not magnetic, so if your jewelry is attracted to a magnet, it's likely not solid gold. However, this test isn't definitive, as some other metals used in jewelry can also be non-magnetic.
Acid Test: Use a testing acid kit specifically designed for gold testing. Scratch the jewelry on a testing stone and apply a drop of testing acid to the scratch. Genuine gold will not react to nitric acid, while gold-plated or fake gold will cause a reaction.
Scratch Test: Real gold is quite soft and malleable, so you can perform a scratch test on an inconspicuous area. Use a sharp object, such as a needle, to gently scratch the surface. If the scratch leaves a mark, it's likely not solid gold.
Professional Appraisal: For a definitive answer, consider getting your jewelry professionally appraised by a jeweler or goldsmith. They have the expertise and tools to accurately assess the composition and value of your jewelry.