A thorianite deposit situated east of the town Tranomaro in the southeastern part of Madagascar. M.Horeau found here in july 1954 crystals of hibonite. This was the 2.known locality for this species.
Ref:
Delbos, L. (1955): "Note sur le gisement d'un mineral nouveau "La hibonite" de l'Androy Mandrareen". Rapp. Ann. Serv. Geol. Mad. 1955