Scientists from Leiden University and Delft University of Technology conducted compositional sediment analyses of a 50,000 year old Neanderthal site, Pech-de-l’Azé I in Dordogne in southwest France. Their results are published here. They found these guys were deliberately selecting manganese dioxide to start fires, not for coloring.
We do not know based off of the archeological and ethnographic records for the selection and use of manganese dioxide for fire starting by hunter gatherers. We do however now have insight that this behavior, this selection for this particular material, is unique and gives a frame of reference for Neanderthal cognitive capacity and extent of natural knowledge. The actions involved in the preferential selection of a specific, non-combustible material are surprising and qualitatively different from the expertise commonly associated with Neanderthals. They aren’t thick headed cavemen.