Classification of Ordinary Chondrites
Channel: Dominik Hezel
Date: 2023-04-12

Ordinary Chondrites (OC) are classified based on the fayalite (fa) and ferrosilite (fs) content of chondrule olivine and pyroxene, respectively. 3 main groups are then discriminated, based on their bulk Fe contents: high-metal (H), low-metal (L), low-iron, low-metal (LL). It seems irritating that the fa and fs contents increase with decreasing bulk chondrite Fe, but this is simply because LL chondrites are more oxidised than H chondrites. Further characteristics of OC are: mostly consisting of chondrules (60-80 vol%) and matrix (~10-15 vol%), minor opaques (2-10 vol%) and rare CAIs (0.1-1 vol%). Average chondrules sizes are between 300 and 900 µm. Si/Mg ratios are elevated compared to solar, and volatile elements are variably depleted relative to solar.