Manganese dendrites

Manganese dendrites, in Cambrian sandstone, north of Bouila, western Queensland. Black manganese oxide minerals are precipitated along cracks and fractures in the rock in a dendritic or branching pattern. To the untrained eye , they can be mistaken for plant fossils, but, unlike fossils,  they are formed much later than the sediments were deposited, and are inorganic in origin. Yellow brown limonite (iron hydroxide ) coats fractures in a similar way.