After a meteorite reaches the Earth’s surface, it is subject to terrestrial weathering. Metallic Fe-Ni grains develop thin red coatings of goethite; the goethite fills pores within the whole-rocks, eventually decreasing their porosity to zero. Other bulk parameters that change during terrestrial weathering of ordinary chondrites are magnetic susceptibility, thermal conductivity, compressive strength, and tensile strength. Evaporite minerals grow on the surfaces of Antarctic finds with phases including Mg carbonates, Mg sulfates, and Ca sulfate. OC whole rocks become contaminated with terrestrial C and water, affecting their bulk isotopic compositions. Frost wedging can cause rocks to expand and shatter as water seeps into fractures and freezes. There are a few OC ventifacts sculpted by wind erosion in arid environments; these rocks typically have three or four flat sides that meet at angular interfaces. A small number of ordinary chondrites are shatter cones, shocked rocks with striated surfaces that have a horsetail-like appearance. Such structures are produced beneath the floors of impact craters.