The morphology and composition of pyrite in sandy podosols in the Swan Coastal Plain.

Seventeen very deep peaty sandy podosol profiles containing distinct A, E, B, coffee rock (spodic B horizon) and C horizons were investigated. Some profiles contain buried soils (Palaeopodosols) representing former levels of the water table. Electron microscopy showed that pyrite is present in these podosols. Synchrotron XRD confirmed the presence of pyrite. Two pyrite morphologies were present: discrete submicron single crystals and 10420 =m framboids. Single crystals of pyrite occurred in all E, B, coffee rock and C horizons examined. X4ray spectra of single crystals and framboids have the pyrite atomic ratio of Fe: S ≈ 1: 2. Framboidal pyrite is present in coffee rock and B horizon. As individual pyrite crystals are very small (≤ 1 =m), they have high specific surface area and are thus potentially very reactive if profiles are aerated.