10 Nov 2014 10 Nov 2014 11 Nov 2014
The Iron skull is located a few minutes after you start the first mission 'Pillar of Autumn' once the Chief has awoke and exited the cryo-tube head to the back of the room and the skull is located behind the large cylinders.
Just walk over it to collect.
Please note skulls only appear in the game whilst playing in the remastered view, skulls do not appear in classic view.
Here's a video to show you.