Mineralogy of manganese dendrites and coatings

Infrared spectroscopic study of desert varnish, manganese dendrites, river deposits, and other manganese oxide concentrations of the terrestrial weathering environment has shown that the morphological distinctions among them have a sound basis in differences in their mineralogy. The manganese oxide in manganese dendrites collected in surface exposures is either romanechite or a hollandite-group mineral. These are mixed with varying amounts of silicate minerals, which are a passive substrate for the oxide deposition. Dendrites collected in underground mine workings are todorokite. Manganese stream deposits are generally birnessite with minor amounts of silicate minerals; one nsutite stream deposit has been identified.
\nCrack deposit mineralogy resembles that of manganese dendrites. Cave and subglacial deposit mineralogy resembles that of manganese stream deposits. Although dendrites have long been considered to be pyrolusite, no example of pyrolusite mineralogy has been identified.