Freshwater Ferromanganese Concretions: Chemistry and Internal Structure

Science  31 Oct 1969:
Vol. 166, Issue 3905, pp. 604-606
DOI: 10.1126/science.166.3905.604


Studies by optical microscopy, x-ray diffraction, and electron probe techniques of ferromanganese concretions from three Canadian lakes reveal chemical banding of amorphous hydrated iron and manganese oxides. The average ratio of iron to manganese in concretions from these lakes varies from 0.43 to 2.56. The concentrations of cobalt, nickel, copper, and lead are one to two orders of magnitude below those reported for oceanic ferromanganese concretions.