Geology of Madagascar

The geology of Madagascar comprises a variety of rocks of Precambrian age which make up the larger part of the east and centre of the island.

[1] The center and eastern portions of the island consist primarily of metamorphic and igneous Precambrian basement granites, migmatites, and schists, ranging in age from 3 billion to 550 million years old.

The Morondava, Mahajanga and Ambilobe sedimentary basins occur along the western third of the island, and consist of terrestrial deposits that range in age from 350 million years ago to recent times.

[5]: 144 Madagascar is the world's leading producer of many colored gemstones, including sapphires, rubies, multi-coloured tourmalines, emeralds, amethysts, cordierites, aquamarines and garnets.

[8] Titanium oxide is found in significant quantities in beach sands located near Toalagnaro, however, 75% of the coastal forest zone in that area would have to be destroyed in order to exploit it, which has not been done.