, at some point in their billion year lives, have been exposed to radiation in one form or another. In the case of Amethyst
, the forming of 'Color Centers' by natural radiation took place when high-speed electrons pierced the mineral's atomic crystal structure, hitting smaller molecules and displacing them. When these molecules were displaced from their regular positions, their place was taken by one of the electrons, which became trapped in the vacant space. This trapped electron absorbed light energy, which caused it to get excited and jiggle. The light energy was then dissipated through the motion of the excited electron, and with it a subset of color wavelengths from the light energy was used up. What we see as the color of an Amethyst
is what light energy wavelengths remain that have not been used up by the excited electron. This is the creation of a 'Color Center,' the phenomenon that gives Amethyst
, topaz and some colored diamonds their color.