Arenite

Arenite (Latin "Arena", sand) is a sedimentary clastic rock with sand grain size between 0.063 mm (0.00256 in) and 2 mm (0.08 in) and contain less than 15% matrix. [ [http://www.britannica.com/eb/article-9009339/arenite Britannica definition of "arenite"] . Accessed on January 1, 2008] The related adjective is "arenaceous". The equivalent Greek-derived term is Psammite, though this is more commonly used for metamorphosed sediments.

Since it refers to grain size rather than chemical composition, the term is used for example in the classification of clastic carbonatic limestones, as the granulometrically equivalent term sandstone is not appropriate for limestone. Other arenites include sandstones, arkoses, greensands and greywackes.

Arenites mainly form by erosion of other rocks or turbiditic re-deposition of sands. Some arenites contain a varying amount of carbonatic components and thus belong to the rock-category of carbonatic sandstones or silicatic limestones. Arenites often appear as massive or bedded medium-grained rocks with a medium- to wide-spaced preferred foliation and often develop a pronounced cleavage.

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:

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