Look at the mark on the inner ring when you buy it. For example, the seal on the inner ring of the emerald thousand gold ring is CL thousand gold. Formal ornaments are stamped (manufacturer's name or abbreviation+purity, according to national regulations, the purity of gold ornaments mainly refers to pure gold and thousands of gold). It's best not to buy one without stamps.
In addition, I want to tell you that gold jewelry is sampled and tested in batches, because gold jewelry testing needs to damage the jewelry first and then carry out spectral analysis, so it is accurate, that is to say, there is basically no testing certificate.
Just keep the bill after you buy it. Don't believe the legend, everyone is buying it. If there are fakes or bad colors, there will be a big fight right away.