PLOS ONE: Middle Stone Age Ochre Processing and Behavioural .
Nov 2, 2016 . A round stone bearing no traces of having been used to process ochre is . and North Africa, information on the way ochre was selected, processed, .. 50 cal kyr BP, ochre residues were found on the inner side of an upper valve of a .. In addition, these three categories may contain quartz, feldspars and.