Definition
Wet soils with an irreversibly hardening mixture of iron, clay and quartz in the subsoil.

Distribution
Active formation of plinthite is taking place in West Africa, parts of South America, India and Western Australia. Ironstone, or hardened plinthite is more widely spread ad often associated with old, high level pene-plains of the southern continents. There are some 60 million hectares of Plinthosols throughout the world; they are often associated with Ferralsols, Acrisols and Alisols.