Alcrete

Alcrete is a type of soil deposit, rich in aluminum. It is generally found in tropical regions, where the parent material is rapidly weathered because of high rainfall and high ambient temperatures. In these conditions, more mobile elements are leached out of the soil, leaving the relatively insoluble Al³⁺ ions behind. A hard, nearly impermeable crust, called a duricrust, may form on or near the surface of such soils. Duricrusts of aluminum-rich soils are called alcrete, or aluminocrete. Alcrete deposits with extremely high concentrations of aluminum are known as bauxite, the source of commercial aluminum ore.