Pelite

Pelite (Greek "Pelos", Clay) is a descriptive name for a clastic rock with a grain size of less than 1/16mm (originally sand or silt) Examples include slate and mudstone. The equivalent Latin-derived term is Lutite. Pelite is more commonly used for a metamorphosed sediment.

"Pilite" is a rarely used name for an altered olivine that has partially pseudomorphically replaced by an assemblage of carbonate–chlorite–actinolite. Pilite can be identified only in a thin section.

Pettijohn [Pettijohn F.J. (1975), "Sedimentary Rocks", Harper & Row, ISBN 0-96-045191-2] gives the following descriptive terms based on grain size, avoiding the use of terms such as clay or argillaceous which carry an implication of chemical composition. The Greek terms are more commonly used for metamorphosed rocks, and the Latin for unmetamorphosed:

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