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An abundant sedimentary rock consolidated from layers of clay and mud. Shale has very fine grains and a laminated structure that fractures easily along the bedding lines. The stone is soft, smooth, and can feel greasy. Shale is composed of clay (>30%) and silica along with smaller quantities of carbonates, feldspars, iron oxides, fossils, and organic matter (called shale oil). Shale oil, or kerogen, is a sulfurous hydrocarbon that can be refined as a source of fuel. Shale can vary in color from gray, brown, black, green, or red. Shale is used in the manufacture of ceramics, tile, and brick. It is also a source of alumina for portland cement.


Synonyms and Related Terms

layered mudstone; skifer (Dan.); Schiefer (Deut.); schiste (Fr.); schalie (Ned.); argilito (Port.)

Sources Checked for Data in Record

  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 703