saprolite

sap·ro·lite  (spr-lt)

n.

Soft, partially decomposed rock rich in clay and remaining in its original place.

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saprolite  (spr-lt)

Soft, thoroughly decomposed and porous rock, often rich in clay, formed by the in-place chemical weathering of igneous, metamorphic, or sedimentary rocks. Saprolite is especially common in humid and tropical climates. It is usually reddish brown or grayish white and contains those structures (such as cross-stratification) that were present in the original rock from which it formed.

Thesaurus

Noun

1.

saprolite - a deposit of clay and disintegrating rock that is found in its original place earth, ground - the loose soft material that makes up a large part of the land surface; "they dug into the earth outside the church"