chert

from WordNet (r) 3.0 (2006)

chert
    n 1: variety of silica containing microcrystalline quartz

from The Collaborative International Dictionary of English v.0.48

Hornstone \Horn"stone`\, n. (Min.)
   A siliceous stone, a variety of quartz, closely resembling
   flint, but more brittle; -- called also {chert}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Chert \Chert\ (ch[~e]rt), n. [Ir. ceart stone, perh. akin to E.
   crag.] (Min.)
   An impure, massive, flintlike quartz or hornstone, of a dull
   color.
   [1913 Webster]

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