Berta Curry (actually it is Joe-JC) wrote:

"I would like to add that each days, sometimes hours, production requires a different handling process, I.E. tweaking."

I agree. The mining engineers and planners know the grades and mineral composition of each of the ore bodies to be mined.

So when they decide to mine a given ore body, they inform the milling department ahead of time what they can expect to be in the feed.

The milling process is then altered based on this information. In other words they are actually custom milling their own ore.

In a big company such as Vale they have their own lab and are constantly analysing both the ore and the in process material at various stages of the process. In fact, the process technology group has a mini lab in each department in addition to the main lab.

They do this for several reasons:

1. So they can adjust the process at all stages to maximize recoveries.

2. So they know how much to charge for the various products sold.

In a big operation such as Sudbury, they often do some milling and refining for other companies....at a fee.

SN