Hostname: page-component-77c89778f8-n9wrp Total loading time: 0 Render date: 2024-07-22T08:40:56.287Z Has data issue: false hasContentIssue false

Medicinal Clay and Spiritual Healing

Published online by Cambridge University Press:  01 January 2024

Ray E. Ferrell Jr.*
Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA
* E-mail address of corresponding author:


The varied mineralogical composition of earthy materials and the quantity of elements extracted by simulated stomach acid substantiate the diversity of materials consumed by humans practicing geophagy. Direct consumption of ‘edible earths’ for medicinal and spiritual purposes occurs worldwide and is deeply rooted in ‘folk medicine’ and religion. The legends associated with the healing powers of the clay from Chimayo, New Mexico, provide an excellent example of the roots of geophagy. The clay mineral assemblages revealed by X-ray diffraction analysis of 22 samples from New Mexico, North America, and other parts of the world are highly variable. One might be monominerallic kaolinite or smectite, and another, a complex mixture of illite, kaolinite, smectite, and chlorite or vermiculite. The quantities of elements (Al, Si, K, Na, Ca, Mg, Fe, Mn, Ti, P, S, Ba, Sr, Pb, Zn, Cd, Co, Cu, Cr, Ni, V, Zr, Se, Mo, Be, Sb, and As) extracted by 0.12 M HCl varied from ∼1.0 mg/g to the limit of detectability, 0.0001 mg/g. Potential long-term human health effects were evaluated with the Reference Dose Ratio (RDR). It divides the quantity of the element extracted from 50 g of the total sample by the recommended reference dose (RfD) reported in the Environmental Protection Agency’s (EPA, USA) IRIS (Integrated Risk Information System) database. Median RDR values for Na, Cr, Sb, and As exceeded 1.0 indicating an abnormally high potential intake. Materials consumed by humans are so varied that caution should be used in comparing the results of one clay study with those of another without mineralogical and chemical data.

Copyright © 2008, The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Abrahams, P W, 1997 Geophagy (soil consumption) and iron supplementation in Uganda Tropical Medicine and Institutional Health 2 617623 10.1046/j.1365-3156.1997.d01-348.x.10.1046/j.1365-3156.1997.d01-348.xCrossRefGoogle ScholarPubMed
Abrahams, P.W. and Selinus, O., 2005 Geophagy and the involuntary ingestion of soil Essentials of Medical Geology Amsterdam Elsevier 435458.Google Scholar
Abrahams, P.W. and Parsons, J.A., 1997 Geophagy in the Tropics: an appraisal of three geophagical materials Environmental Geochemistry and Health 19 1922.Google Scholar
Barltrop, D. Strehlow, C.D. Thornton, I. and Webb, J.S., 1974 Significance of high soil lead concentrations for childhood burdens Environmental Health Perspectives 7 7582 10.1289/ehp.74775.CrossRefGoogle ScholarPubMed
Carretero, M.I. and Lagaly, G., 2007 editors () Clays and health: An introduction. Applied Clay Science, 36, 13.Google Scholar
Carretero, M.I. Gomes, C.S.F. Tateo, F., Bergaya, F. Theng, B.K.G. Lagaly, G., 2006 Clays and human health Handbook of Clay Science Amsterdam Elsevier 717741 10.1016/S1572-4352(05)01024-X.CrossRefGoogle Scholar
Dissanayake, C., 2005 Of stones and health: Medical geology in Sri Lanka Science 309 883885 10.1126/science.1115174.10.1126/science.1115174CrossRefGoogle ScholarPubMed
Ferrell, R.E., Vermeer, D.E., and LeBlanc, W.S. (1985) Chemical and mineralogical composition of geophagical materials. Trace Substances in Environmental Health XIX, Universityof Missouri, pp. 4755.Google Scholar
Gelfand, M.C. Zarate, A. and Knepshield, J.H., 1975 Geophagia: A cause of life-threatening hyperkalemia in patients with chronic renal failure Journal of the American Medical Association 234 738 10.1001/jama.1975.03260200054019.10.1001/jama.1975.03260200054019CrossRefGoogle ScholarPubMed
Gomes, C.S.F. and Silva, J.B.P., 2007 Minerals and clay minerals in medical geology Applied Clay Science 36 421 10.1016/j.clay.2006.08.006.CrossRefGoogle Scholar
Hooda, P.S. Henry, C.J.K. Seyoum, T.A. Armstrong, L.D.M. and Fowler, M.B., 2004 The potential impact of soil ingestion on human mineral nutrition Science of the Total Environment 333 7587 10.1016/j.scitotenv.2004.04.023.CrossRefGoogle ScholarPubMed
Hunter, J.M. and de Kleine, R., 1984 Geophagy in Central America The Geographical Review 74 157168 10.2307/214097.10.2307/214097CrossRefGoogle ScholarPubMed
Hunter, J.M. Horst, O.M. and Thomas, R.N., 1989 Religious geophagy as a cottage industry: The holy clay tablet of Esquipulas, Guatemala National Geographic Research 5 281295.Google Scholar
Gonzalez, J.J. Owens, W. Ungaro, P.C. Werk, E.E. and Wentz, P.W., 1982 Clay ingestion: a rare case of hypokalemis Annals of Internal Medicine 97 6566 10.7326/0003-4819-97-1-65.CrossRefGoogle Scholar
Johns, T. and Duquette, M., 1991 Detoxification and mineral supplementation as functions of geophagy American Journal of Clinical Nutrition 53 448456 10.1093/ajcn/53.2.448.CrossRefGoogle ScholarPubMed
Katz, J.M. (2008) Hungry Haitians eat mud as cost of food soars. The Advocate, Wednesday, January 30, 2008, p. 3A.Google Scholar
Ljung, K. Selinus, O. Otabbung, E. and Berglund, M., 2006 Metal and arsenic distribution in soil particle sizes relevant to soil ingestion by children Applied Geochemistry 21 16131624 10.1016/j.apgeochem.2006.05.005.CrossRefGoogle Scholar
Mahaney, W.C. and Krishnamani, R., 2003 Understanding geophagy in animals: Standard procedures for sampling soils Journal of Chemical Ecology 29 15031523 10.1023/A:1024263627606.CrossRefGoogle ScholarPubMed
Mascolo, N. Summa, V. and Tateo, F., 1999 Characterization of toxic elements in clays for human healing use Applied Clay Science 15 491500 10.1016/S0169-1317(99)00037-X.10.1016/S0169-1317(99)00037-XCrossRefGoogle Scholar
Minnich, V. Orcuoglu, A. Tarcon, Y. Argosy, A. Cin, S. Yorupoglu, O. Raenda, F. and Demirag, B., 1968 Pica in TurkeyII: Effect of clayupon iron absorption American Journal of Clinical Nutrition 21 7886 10.1093/ajcn/21.1.78.CrossRefGoogle ScholarPubMed
Oomen, A.G. Hack, A. Minekus, M. Zeijdner, E. Cornelis, C. Schoeters, G. Verstraete, W. van de Wiele, T. Wragg, J. Rompelberg, C.J.M. Sips, A.J.A.M. and van Wijnen, J.H., 2002 Comparison of five in vitro digestion methods to study the bioaccessibility of soil contaminants Environmental Science and Technology 36 33263334 10.1021/es010204v.CrossRefGoogle Scholar
Padilla, F.V. and de la Torre, A.M., 2006 La pica: retrado de una entidad clinica poco conocida Nutricion Hospitalaria 21 557566.Google Scholar
Petschick, R. (2004) MacDiff 4.2.5. Powder diffraction software. Available from: .Google Scholar
Reinbacher, W.R. (2003) Healing Earths: The Third Leg of Medicine. Published by the author, ISBN: 1-4033-5090-5, 244 pp.Google Scholar
Robertson, R.H.S., 1986 Fuller’s Earth: A History of Calcium Montmorillonite London Volturna Press, Mineralogical Society occasional publication.Google Scholar
Robertson, R.H.S., 1996 Cadavers, choleras, and clays Mineralogical Society Bulletin 113 37.Google Scholar
Ruby, M.V. Davis, A. Schoof, R. Eberle, S. and Sellstone, C.M., 1996 Estimation of lead and arsenic bioavailabilty using a physiologically based extraction test Environmental Science and Technology 30 422430 10.1021/es950057z.10.1021/es950057zCrossRefGoogle Scholar
Smith, B. Rawlins, B.G. Cordeiro, M.J.A.R. Hutchins, M.G. Tiberindwa, J.G. Sserunjogi, L. and Tomkins, A.M., 2000 The bioaccessibility of essential and potentially toxic trace elements in tropical soils from Mukono District, Uganda Journal of the Geological Society of London 157 885891 10.1144/jgs.157.4.885.CrossRefGoogle Scholar
Tateo, F. and Summa, V., 2007 Element mobilityin clays for healing use Applied Clay Science 36 6476 10.1016/j.clay.2006.05.011.CrossRefGoogle Scholar
Tateo, F. Summa, V. Gianossi, M.L. and Ferrero, G., 2006 Healing clays: Mineralogical and geochemical constraints on the preparation of clay-water suspension (‘argillic water’) Applied Clay Science 33 34 10.1016/j.clay.2006.05.004.CrossRefGoogle Scholar
Vermeer, D.E. and Ferrell, R.E., 1985 Nigerian geophagical clay: A traditional antidiarrheal Science 227 634636 10.1126/science.3969552.CrossRefGoogle Scholar
Vermeer, D.E. and Frate, D.A., 1979 Geophagy in rural Mississippi: Environmental and cultural contexts and nutritional implications American Journal of Clinical Nutrition 32 21292135 10.1093/ajcn/32.10.2129.CrossRefGoogle ScholarPubMed
Williams, L.B. Holland, M. Eberl, D.D. Brunet, T. and de Brunet Courrsou, L., 2004 Killer Clays! Natural antibacterial clay minerals Mineralogical Society Bulletin 139 38.Google Scholar
Williams, L.B. Haydel, S.E. Giese, RS Jr. and Eberl, D.D., 2008 Chemical and mineralogical characteristics of French green clays used for healing Clays and Clay Minerals 56 437452 10.1346/CCMN.2008.0560405.CrossRefGoogle ScholarPubMed
Wilson, M.J., 2003 Clay mineralogical and related characteristics of geophagic materials Journal of Chemical Ecology 26 15251547 10.1023/A:1024262411676.CrossRefGoogle Scholar