ferrugineous
/fɛrʊˈdʒɪnɪəs/adjective
1Resembling iron rust in colour; of a reddish brown.
2Containing iron, especially in the form of hydrated oxides.
Origin
Mid 17th century; earliest use found in Thomas Johnson (d. 1644), apothecary and soldier. From classical Latin ferrūgineus of a dark brownish colour, (of taste) rusty + -ous.