gems, corundum, Madagascar.12

Alfred Lacroix (1922–1923) began, in his Minéralogie de Madagascar, the description of corundum and its deposits on the Great Island: Corundum appears in Madagascar in two different forms of economic interest: the first in enormous opaque crystals and granular masses, which are exploited by the ton for the abrasive industry; the second in very small-sized crystals, but frequently transparent and therefore usable as gemstones. Only the deposits of the first type are certainly known in situ.""