“Color is a false friend, it doesn’t help to recognize a stone,” explains Didier Nectoux, “quartz may, for example, be purple, yellow or black.” Based on this observation, the director of the Musée de Minéralogie at ParisTech, who sites his own color blindness, offers introductory sessions to gemstones for the blind where they can scratch gypsum and quartz or listen to the sound of a drop of acid on calcite. An excellent initiative!