argillite

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1. any compact sedimentary rock composed mainly of clay materials; clay stone.

noun

1. any argillaceous rock, esp a hardened mudstone

1. A highly compacted sedimentary or slightly metamorphic rock consisting primarily of particles of clay or silt. Argillite differs from mudstone in that it does not have the same fine laminations, and from shale and slate in that it is not fissile.

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