Hydrated iron oxides are compounds formed when iron oxides combine with water molecules. They typically occur in nature as minerals, such as goethite and limonite, and are often found in soils and sediments. These compounds can vary in color, ranging from yellow to brown, and play a significant role in the Earth's geochemical processes. These hydrated forms of iron oxides are important for various applications, including water treatment and pigment production. They can also influence the mobility of heavy metals in the environment, making them relevant in studies of soil contamination and remediation efforts.