  The mineralogy and physical properties of Chelyabinsk meteorites (fall,
February 15, 2013) are presented. Three types of meteorite material are
present, described as the light-colored, dark-colored, and impact-melt
lithologies. All are of LL5 composition with the impact-melt lithology being
close to whole-rock melt and the dark-colored lithology being shock-darkened
due to partial melting of iron metal and sulfides. This enables us to study the
effect of increasing shock on material with identical composition and origin.
Based on the magnetic susceptibility, the Chelyabinsk meteorites are richer in
metallic iron as compared to other LL chondrites. The measured bulk and grain
densities and the porosity closely resemble other LL chondrites. Shock
darkening does not have a significant effect on the material physical
properties, but causes a decrease of reflectance and decrease in silicate
absorption bands in the reflectance spectra. This is similar to the space
weathering effects observed on asteroids. However, compared to space weathered
materials, there is a negligible to minor slope change observed in impact-melt
and shock-darkened meteorite spectra. Thus, it is possible that some dark
asteroids with invisible silicate absorption bands may be composed of
relatively fresh shock-darkened chondritic material.
