This is gypsum.  The sample is placed on a black anodized aluminum plate. The illumination was by the red, green, and blue LEDs in the optical head.  This image is a composition from 3 monochrome images. The individual images are shown in thumbnail below. Clicking on the color name will take you to a full size view.  The UV image is mostly thermal noise and stray light in the room. 

             Red ( Full Size View)                             Green ( Full Size View)                        Blue ( Full Size View)                            UV ( Full Size View)