Mainly brightness, density, quality, ore body composition (artificial or processed), gem refractive index, etc. There should be only a few main items, and then the brightness on the bright surface is the bare brightness of the gem, the transparent and pure brightness is of high quality, and the density is its density. Generally speaking, the density is better, and the quality is how big the topaz is. Ore body composition is generally natural, or semi-finished products, that is, second-class or defective.