Famous specimens from Germany (Solnhofen), Morocco, and the United States; these are not crystalline minerals but surface pseudomorphs: thin, branched films of manganese oxides/hydroxides precipitated along fractures and bedding planes of sedimentary rocks (often limestone) through capillary infiltration of Mn-rich solutions that oxidize upon contact with air. The fractal pattern resembles the shape of fossil plants, hence the name (from the Greek dendron, meaning “tree”).

Highly prized by collectors and enthusiasts of decorative slabs for their natural pattern resembling a landscape or a fern; used in decorative slabs for flooring and wall coverings; sometimes mistaken for real fossils.