Columbia River Sand, US-Canada Boundary
Two blast furnace slag particles are present in this sample. They are evident by the lack of reflection in the opaque particles. The black blast furnace slag particles are glass with inclusions. They are not conductive and have low refractive indices relative to the black metal oxides. The black metal oxides are much better reflectors because they tend to be semi-conductors and have real refractive indices far from 1.680, the mounting medium used in this case.
Transmitted Circular Polarized Light and Reflected Darkfield Illumination
