tansk81,
As Dhuy stated, the impurities are very low, which is good for SDL. Compare yourslef for proof. Also taken from the latest report:
Itabirite +66% Fe concentrate with around 44% weight recovery and very low phosphorus and alumina content
SDL's 44% recovery is better than most other companies %weight of around 35% to 40%. So SDL is still a cut above the rest.