SPECTRUM

This colorful image shows a dark band at the 650 mark, indicating this piece of jadeite jade has been dyed.

Photo courtesy of Scott Papper, GIA GG, AJP, CMA (NAJA), Global Gemology & Appraisals

A gemstone's absorption spectrum describes the specific bands of light that are absorbed by the gem, and the bands that pass through it.

Gemologists will sometimes use a spectroscope to measure a gem's absorption spectrum, to help with gem identification.