Black ordinary chondrites - An analysis of abundance and fall frequency

Black ordinary chondrite meteorites sample the spectral effects of shock on ordinary chondrite material in the space environment. Since shock is an important regolith process these meteorites provide insight into the spectral properties of the regoliths on ordinary chondrite parent bodies. To determine how common black chondrites are in the meteorite collection and, by analogy, the frequency of shock-alteration in ordinary chondrites, several of the world's major meteorite collections were examined to identify black chondrites. Over 80 percent of all cataloged ordinary chondrites were examined and, using an optical definition, 61 black chondrites were identified. Black chondrites account for approximately 13.7 percent of ordinary chondrite falls. If the optically altered gas-rich ordinary chondrites are included the proportion of falls that exhibit some form of altered spectral properties increases to 16.7 percent. This suggests that optical alteration of asteroidal material in the space environment is a relatively common process.