This is a very interesting post I found on there, especially as its based on the minimum 48% required, however KAB will supply higher grades than this and will therefore earn more. COURTESY OF WORLDSTOCKS FORUM :
Hopefully I can help enlighten some of my fellow non-professionals on here following some of my research.
Definition of DMTU (Iron ore, but it gives you an idea):
"A Dry Metric Tonne (Ton) Unit (dmtu) is the internationally agreed-upon unit of measure for iron ore pricing. It has the same mass value as a metric tonne, but the material has been dried to decrease the moisture level.
A dry metric ton unit consists of 1% of iron (Fe) contained in a tonne of ore, excluding moisture. The price per tonne of a certain quantity of iron ore is calculated by multiplying the cents/dmtu price by the percentage of iron content. Iron ore contracts are quoted in US Cents."
BHP Billitons reference price for Manganese Ore in Feb 2012, CIF was USD 4.75 per DMTU (see second paragraph):