X-ray diffraction and selective chemical dissolution methods were used to investigate the composition of Mn oxide minerals in Fe-Mn nodules of several main types of soils in China. The changes of relative intensity of X-ray diffraction patterns were studied both before and after chemically selective dissolution. It was found that lithiophorite was a common Mn oxide in all examined Fe-Mn nodules. Todorokite, however, was a predominant Mn oxide in Fe-Mn nodules in caf-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules of arp-udic Luvisols in Wuhan and Zaoyang, Hubei Province, contained birnessite and vernadite. Hollandite was found in Fe-Mn nodules of alt-udic Ferrisols of Yizhang, Hunan Province; arp-udic Luvisols of Zaoyang, Hubei Province; and cal-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules in alt-udic Ferrisols of Guiyang, Hunan Province, had a few coronadites. Mineralogy of Mn oxide minerals in soil Fe-Mn nodules was related to soil environment, soil types and quantities of relevant cations.
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