Rock fragment

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A sand grain that would be classified as a rock fragment. In this case, the rock fragment would be a volcanic rock fragment. Scale box in millimeters, plane-polarized light on top, cross-polarized light on bottom.

A rock fragment, in sedimentary geology, is a sand-sized particle or sand grain that is made up of multiple grains that are connected on the grain scale. These can include grains which are sand-sized themselves (a granitic rock fragment), or finer-grained materials (shale fragments).[1] This definition is used for QFR ternary diagrams, provenance analysis, and in the Folk classification scheme, mainly in sandstones.


  1. ^ "sedimentary rock - Classification of sandstones". Encyclopedia Britannica. Retrieved 2017-08-12.
  • Folk, R.L., 1974, Petrology of Sedimentary Rocks: Austin, TX, Hemphill Press, second edition, 182 p.