“…It would appear, however, that in regions where Ca is absent or in low concentration, Ba may take its place. In the Groote Eylandt manganese ore body, G quarry, the ore contains CaO 0.03~o, BaO 1.7~, K20 0.5 ~, and MgO 0.4 ~, and here a Ba-containing todorokite occurs (Ostwald, 1982a). In the Cretaceous-age sediments which enclose the stratiform manganese oxide deposit, disseminated carbonate ooliths occur in association with a Ca-containing todorokite (Ostwald, 1982b).…”