silcrete

silcrete, silica-rich duricrust, an indurated, or hardened, layer in or on a soil. It generally occurs in a hot, arid climate where infrequent waterlogging causes silica to dissolve and be redeposited to cement soil grains together. Silcrete is extremely hard and resistant to weathering and erosion but eventually weathers spheroidally to produce boulders and angular fragments. Inselbergs and other residual hills are often capped by a silcrete layer. In the semidesert of Western Australia, an extensive deposit, almost 10 m (30 feet) thick, has developed from a granite-gneiss parent material.