Vis-NIR reflectance spectra of powdered olivine, pyroxene, smectite and silica at 4 different grain sizes (from sub-µm to 200 µm) and with sub-µm grains in compact or porous surfaces

We measured the reflectance spectra (from 0.5 to 4.2 µm) of powders of olivine, pyroxene, a smectite-rich material, and amorphous silica. The powders were grinded and sieved and the spectra of four size fractions were measured: 100-200 µm, 50-100 µm, 0-50 µm, and sub-micrometer sized grains. In addition, porous surfaces of the latter grains were produced by mixing them with water ice and sublimating the ice.