I would guess, this was not x-ray photography, but spectroscopy: https://en.wikipedia.org/wiki/X-ray_spectroscopy https://en.wikipedia.org/wiki/X-ray_spectrosco

I would guess, this was not x-ray photography, but spectroscopy: https://en.wikipedia.org/wiki/X-ray_spectroscopy https://en.wikipedia.org/wiki/X-ray_spectroscopy There are these slick handheld units that exist, where you basically point them at something, and they tell you what elements are in something! https://www.youtube.com/watch?v=LWPSrXB2OZw https://www.youtube.com/watch?v=LWPSrXB2OZw