i have read so much & understand, page-87

JL sorry I missed your question. The oxygen goes off on the boat with the Fe. If you could produce a 100% pure magnetite concentrate then 72.36% of its weight would be Fe and 27.64% of its weight would be oxygen. In reality you can not concentrate it to this degree so you are left with impurities. The major ones generally being SiO and Al2O3. The final Fe grade over 62% Fe determines the premium the ore will receive in the market, the impurity levels generally will discount the price if they are outside acceptable levels.

Attached is a link to a GBG August 2008 presentation which details the expected Karara Concentrate Specifications on page 18. Makes interesting reading aside from page 18.

http://gindpublic.powercreations.com.au/images/gind---aethiziphi.pdf

P.S I do not work or have ever worked for GBG or KLM (or their contractors) and do not endorse any information on the above link and no one should consider or rely on my posts in making any investment decision. They are for general information only and may be subject to error.