Archaic period bone in Southeast Missouri characteristically displays a patchy black and reddish brown staining not found on bone from other-aged sites in the area. The stained areas appear to be post-depositional additions to the bone matrix. Preliminary tests suggest that the stain is inorganic and is rich in Mn and Fe. Here, electron microbeam analysis is used in conjunction with SEM imaging to identify elements specifically linked to the staining. Commparisons are made between the elemental composition of bone and associated sediments from several different-aged occupations. Variability in post-depositional environment between occupations is documented and related to the presence of staining. -- CAL