Description and chemical composition of ferromanganese deposits from Oneida Lake, New York

The crusts usually have a crude concentric banding owing to an alternation of orange, iron-rich layers and black, iron-poor layers. Materials from both types of layers are x-ray amorphous.

The Oneida lake crusts, like most other freshwater manganese nodules, contain about the same Mn concentration as marine manganese nodules, but are usually higher in Fe and lower in trace metals than their marine equivalents. Although Fe and Mn may be precipitating directly from the lake water, it is more likely that the oxidate crusts are the result of precipitation of Fe and Mn when reduced sediment pore water comes in contact with well oxygenated bottom waters.