Trace or chromogenic elements contained in gems absorb light, and the characteristic absorption spectra of various gems are different. Characteristic absorption peak means that an unknown gem can see an absorption peak at a specific position in the spectrum (at this time, the area of the absorption peak is black), which largely "implies" that this gem is a gem. Jewelry appraisal needs a variety of instruments to reach a conclusion.

The teacher said that only green jadeite has characteristic absorption spectrum, and if purple also has it, it is either Mn spectrum or Fe spectrum, because the color-causing elements of purple jadeite are controversial.