gothite

from WordNet (r) 3.0 (2006)

gothite
    n 1: a red or yellow or brown mineral; an oxide of iron that is
         a common constituent of rust [syn: {goethite}, {gothite}]

from The Collaborative International Dictionary of English v.0.48

Gothite \G["o]"thite\, gothite \go"thite\, or Goethite
\Goe"thite\, n. [After the poet G["o]the.] (Min.)
   A hydrous oxide of iron ({HFeO2}), occurring in prismatic
   crystals, also massive, with a fibrous, reniform, or
   stalactitic structure. The color varies from yellowish to
   blackish brown.
   [1913 Webster]