Buying gold-plated jewellery when looking for the real deal is a common trap into which many first-time gold buyers fall. Gold-plated jewellery is pot metal or silver that is covered in a layer of real gold, of varying quality and thickness. If it is high-quality plate, you can easily mistake it for jewellery made of 100% real gold. For these reasons, it is important to learn methods for determining whether a "gold" item is real or plated.
Check the edges. Gold plate rubs off if it wasn't very thick to begin with or if the jewellery was worn a lot. This means the edges may be worn down or losing their plate. If you see patches where the lustre of the gold doesn't seem true, it's probably not real. Real gold has a dull, matt lustre.
Look for marks. The most common marks on gold plate are HGE (gold electroplate) and RGP (rolled gold plate). If you see one of these, you know you are not holding a piece of pure gold.
Use a magnet. Buy a large horseshoe-shaped auto shop magnet. Run the jewellery in question along it. Real gold will not be attracted to the magnet, while plated metal will be. Perform this procedure slowly, since the magnet might not be strongly attracted to a heavily plated piece.
Test the jewellery with an electronic gold tester. These can be purchased online, though they can cost several hundred dollars. However, they are the most reliable indicators. Commonly available acid test kits are much cheaper but are not recommended. They do not always produce reliable results.