I was wondering about the physics of color, and now am interested in finding out if there are any resources (databases, text files, html tables, or pdf listings) of minerals and their associated colors or (ideally) color wavelength spectrum.
For example, amethyst might have a white, silver, and purple color spectrum. Onyx might have a grey, blue, or black color spectrum. Granite another spectrum. Wondering (a) if any of this information is captured in any form on the web (such as 1 journal article per mineral/rock type), and (b) if it is aggregated into a database, text file, table, or other sort of list which includes lots of types, so it would say the wavelength of visible light that it emits, or some ranges of it, or even a hex color range.