Human Geophagia, Calabash Chalk and Undongo: Mineral Element Nutritional Implications Abrahams, Peter W. ; Davies, Theo C. ; Solomon, Abiye O. ; Trow, Amanda J. ; Wragg, Joanna Abstract Publication: PLoS ONE Pub Date: January 2013 DOI: 10.1371/journal.pone.0053304 Bibcode: 2013PLoSO...853304A