Flint wall

Flint \Flint\, n. [AS. flint, akin to Sw. flinta, Dan. flint;
   cf. OHG. flins flint, G. flinte gun (cf. E. flintlock), perh.
   akin to Gr. ? brick. Cf. {Plinth}.]
   1. (Min.) A massive, somewhat impure variety of quartz, in
      color usually of a gray to brown or nearly black, breaking
      with a conchoidal fracture and sharp edge. It is very
      hard, and strikes fire with steel.
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   2. A piece of flint for striking fire; -- formerly much used,
      esp. in the hammers of gun locks.
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   3. Anything extremely hard, unimpressible, and unyielding,
      like flint. "A heart of flint." --Spenser.
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   {Flint age}. (Geol.) Same as {Stone age}, under {Stone}.

   {Flint brick}, a fire made principially of powdered silex.

   {Flint glass}. See in the Vocabulary.

   {Flint implements} (Arch[ae]ol.), tools, etc., employed by
      men before the use of metals, such as axes, arrows,
      spears, knives, wedges, etc., which were commonly made of
      flint, but also of granite, jade, jasper, and other hard
      stones.

   {Flint mill}.
      (a) (Pottery) A mill in which flints are ground.
      (b) (Mining) An obsolete appliance for lighting the miner
          at his work, in which flints on a revolving wheel were
          made to produce a shower of sparks, which gave light,
          but did not inflame the fire damp. --Knight.

   {Flint stone}, a hard, siliceous stone; a flint.

   {Flint wall}, a kind of wall, common in England, on the face
      of which are exposed the black surfaces of broken flints
      set in the mortar, with quions of masonry.

   {Liquor of flints}, a solution of silica, or flints, in
      potash.

   {To skin a flint}, to be capable of, or guilty of, any
      expedient or any meanness for making money. [Colloq.]
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