Gossan

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Gossan \Gos"san\, n. (Geol.)
     Decomposed rock, usually reddish or ferruginous (owing to
     oxidized pyrites), forming the upper part of a metallic vein.
     Called also {iron hat}.
     [1913 Webster]