are named from the Greek word déndron, meaning
tree in alusion to their typical tree-like branched
forms. Dendritic forms are often mistaken for fossils
of mosses or other plant growths. These are sometimes
referred to as pseudofossils. Dendrites form when naturally occurring fissures in minerals
such as Quartz or
rocks such as limestone are filled by percolating water rich in manganese and iron and
then flows along the fractures and bedding planes depositing dendritic crystals as the solution flows through.
Dendrites can be found trapped as inclusions within
many types of minerals such as Quartz, Beryl and Chabazite.
Dendrites can also be found on the surfaces of rocks
such as limestone, sandstone and schist. Both of these
types of dendrites can be found at many localities around
Dendrites are often attributed to the mineral
Pyrolusite but testing by infra-red spectroscopy has
shown that no known manganese dendrites are Pyrolusite
but may consist of other similar black manganese oxides
such as Birnessite, Coronadite, Cryptomelane, Hollandite,
Romanèchite, Todoroite or other species. Potter and Rossman (1979) have found that infra-red
spectroscopy has been helpful in verifying some dendrite mineralogy.
and Rossman 1979, Mineralogy of Manganese Dendrites and Coatings,
American Mineralogist, v. 64, p. 1219-1226.