Saprolite

Saprolite (from the Greek. Σαπρος - rotten) is a crystalline rock, highly decomposed by natural chemical weathering . Usually soft and, being at the site of the primary occurrence of relict rocks, preserves their structure and texture. In addition to intact decomposition of relict minerals, it mainly contains quartz and a high percentage of kaolinite and other clay-forming minerals. Further weathering of saprolite leads to the formation of laterite soils.