New Caledonia ( French : Nouvelle-Cal Ã donie ; popular names : Kanaky , Le caillou ) is a `` sui generis collectivity '' ( in practice an overseas territory ) of France , made up of a main island ( Grande Terre ) and several smaller islands . New Caledonia ( French : officially : Nouvelle-Cal Ã donie ; colloquially : ( la ) CalÃ donie ; popular nickname : ( le ) Caillou ) , has a special status of sui generis collectivity of France .