The black pearl production scarce, precious comparison. People often dyed black pearls to sell.
The other method is to soak in the color of pearls with silver nitrate solution, dried out after that dyed Huihei or pure black.
Natural black pearl is not pure black, but with a slight rainbow-like flash of dark blue or black with a bronze hue. Dyeing is not pure black, uniform color, luster poor. Dip by 5% nitric acid Mianqian cleans pearls, not Diaose natural pearls, pearls and stained black stains left behind. Natural pearls delicate surface smooth, stained black pearl beads surface layer are often corrosion, corrosion can be seen traces of minor crease and natural spots or powder.
Natural pearls and cultured pearls identification of natural pearls delicate texture of uniform thickness pearls, sustained grave-like translucent, shiny strong. Cultured Pearls of pearls and thin, better transparency, gloss than natural pearls, and the shape of natural pearls and more irregular, smaller diameter, and a sustained round cultured pearls, large head, often pit the surface, loose texture. To strong light, slowly rotating pearls, in the proper position to see cultured pearl beads nuclear flash. Two 360-degree flash general, the beads can also be seen in light and shade-and parallel stripes.