Iron oxide

Iron oxide is a quest item used in One Small Favour and One of a Kind. It is obtained by talking to Tindel Marchant in Port Khazard. The player is asked to stuff the Marchant's stodgy mattress in return for the iron oxide. The oxide must then be taken to Wizard Cromperty in Ardougne in order to complete the next step in the quest. If lost, Marchant will charge you 200 coins for a new one.

During One of a Kind, Iron oxide is obtained by examining the weapon rack in Robert the Strong's library.

Trivia

 * The examine is accurate because Iron(III) oxide is the chemical name for rust.