Abstract: | Abstract— Natural calcium monoaluminate, CaAl2O4, has been found in a grossite‐rich calcium‐aluminum‐rich inclusion (CAI) from the CH chondrite Northwest Africa 470. The calcium monoaluminate occurs as colorless ~10 μm subhedral grains intergrown with grossite, perovskite, and melilite. Nebular condensation is the most likely origin for the precursor materials of this CAI, but calculations suggest that dust/gas ratios substantially enhanced over solar are required to stabilize CaAl2O4. |