Manure-derived inorganic components are particularly important in controlling phosphorus (P) retention in dairy manure-amended sandy soils because of the absence of native P sorbing minerals. This study focused on the inorganic components in heavily manure-amended soils and their potential association with P. Samples were collected from manure-amended soils at three active and three abandoned dairies from Florida (Total P ranges 1200-3000 mg P/kg). Particle-size and density fractionations were performed, along with various selective dissolution procedures. Mineralogy and elemental composition of the resulting materials were determined by x-ray diffraction (XRD), electron microscopy (EM), and energy-dispersive x-ray elemental analysis (EDS). EM images of light density (<2.0 SG) fraction showed abundant phytoliths and dominance of Si. The >2.0-SG fraction was predominantly quartz. No P bearing minerals have yet been identified. Microprobe analysis revealed that Mg was correlated spatially with P much more than was Ca for active dairies, but the reverse was true for abandoned dairies Results suggest that Mg as well as Ca is associated with P, which has implications for P solubility. Noncrystalline Si could be a factor in P sorption properties.