These dendrites may consist of birnessite, coronadite, cryptomelane, hollandite, romanèchite, todorokite or other species. Many manganese minerals have similar chemistry and X-ray powder patterns and usually show line-broadening in dendrites, due to their poor crystallinity, which can make X-ray diffraction identification ineffectual. Potter and Rossman (1979) have found that infra-red spectroscopy has been helpful in verifying some dendrite mineralogy. Currently, there are no known manganese dendrites in the world which contain pyrolusite (Potter & Rossman, 1979).
Visit for more detailshttp://www.mindat.org/min-26645.html