Calcium Monoaluminate

Mineral, CaAl2O4. The only known natural occurrence of this mineral is in a grossite-rich inclusion in the CH chondrite NWA 470 (Ivanova et al., 2002).

From the 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 mm 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.

Some or all content above used with permission from J. H. Wittke.