Another 80% is nickel extracted from saprolite. Weathering mantles made up of saprolite are common in Europe. Aquifers in Western Australia are of saprolite grit. Mantles of kaolinitic saprolite are common in Western and Northern Europe. Cobalt is also being produced here from saprolite deposits. In lower saprolite zones, plagioclase weathered to kaolin. Placer estimated the combined primary, saprolite and alluvial reserves of the Omai gold deposits. More intense weathering results in a continuous transition from saprolite to laterite. Intensive weathering has created thick zones of saprolite and heavily weathered soils. Most of the gold was found in eroded rock (saprolite) and mixed in with quartz. The texture, pH and mineral constituents of saprolite are inherited from its parent material. Saprolite composition varies from kaolinitic and ferrallitic to grus. Within the lower saprolite, violarite is transitional with unaltered pentlandite-pyrite-pyrrhotite ore. Residuum differs from saprolite through its structure and degree of weathering. The Swaziland Middleveld is dominated by soils and saprolite, formed out of diorite and granodiorite.