Umov laws for mineral and silica mixture samples that use different albedo definitions. The square and diamond endmembers are from Spadaccia et al. (2022) and Sultana et al. (2023), respectively (see Sect. 2 for details). Silicate-carbon mixture samples and Ceres and Vesta are shown for comparison (see Fig. 3). The abbreviations are as follows: si: silica, mt: magnetite, spi: spinel, graph: graphite, fo: forsterite, fa: fayalite, ol: olivine, and FeS: iron sulfide. Binary and tertiary mixtures are indicated by connecting endmembers with a hyphen (“-”) in the legend.