Among them, white with rose red is the best, and blue-black with metallic luster is the best. But if you see obvious black-gray pearls, you should be on your guard. It may be dyed pearls.
The methods to distinguish dyed pearls from real pearls are: natural black pearls are not pure black, but dark blue black with rainbow-like flash or black with bronze hue; Dyed pearls are grayish black and black, with monotonous color and poor luster. If you scrub pearls with a little 5% dilute nitric acid, there will be black marks on the cloth.
Consumers should pay special attention when buying expensive black pearls. Judging from the appearance of pearls, each pearl is different in size and shape; Look at the luster of pearls, real pearls give off soft light under the light, while artificial pearls have no luster; When two pearls rub against each other, pearl powder will appear on the surface, but if the powder is wiped off by hand, the surface of the beads will be as bright as ever.