The color world of gemstones
An object that absorbed all light waves would appear completely black. Our eye picks up these (reflected) light waves through sensory cells in the eye called "cones" and passes the stimuli on to our neural system, which converts the stimuli into color. Humans, by the way, can only perceive colors in a spectrum of about 390nm (violet) to 700nm (dark red). However, there are many animal species that can see other colors.
The decisive factor is therefore the nature of a gemstone and which light waves it absorbs, or which it reflects again. A distinction is made between intrinsically colored (idiochromatic) stones, in which the color is created by the mineral structure itself, and extrinsically colored (allochromatic) gemstones, in which the color is created by inclusions of foreign substances. A rose quartz, for example, is nothing more than simple silica (quartz) with phosphorus or titanium ions incorporated into its crystal structure, which ultimately give the rose quartz its coloration.