Sapphires from the Andranondambo mine in SE Madagascar

Superb royal blue sapphire of about 4 ct (Source D, Bangkok)

Furthermore, hibonite (Ca,REE,Th)(Al,Ti,R2+)12O19) with Ti= Ti, Si, R2+ = Mg2+, Fe2+, Zn2+; Al = Al3+, Fe3+ and REE = Sm3+, Nd3+, Ce3+, La3+ - a rare mineral thought to exist in meteorites only - occurs at Andranondambo together with sapphires (exact chemical analyses of a hibonite from this locality see Rakotondrazafy et al., 1996).

The classical expert in Malagasy mineralogy, A.Lacroix (1922), summarizes that corundum is frequently associated with metamorphous rock suites. Gem quality corundum, has, however, rarely been found heretofore and the production was mainly limited to relatively small pieces of low quality.