Fe2O3*0.6994=Fe content

Fe*1.43= Fe2O3

Thank you for your answer but the FeO% in BIF are lesser than 1% if applying this equation the results are inconsistent Mostafa Feiz

Are you work on some BIF layers? If FeO wt% is lesser than 1 wt%, then how much Fe2O3 content or Fe was detected? Reda Chatiby

Dear Reda Chatiby , If you don't know the average content of Fe in the BIF layers please study this article that may help you:

[BIF-hosted iron mineral system: A review ,S.G. Hagemann a, et al. 2015]

DOI: 10.1016/j.oregeorev.2015.11.004

dear Feiz thank you for your prompt and fruitful answers

best wishes

Atomic weight for Fe = 55.85

Atomic weight for O = 16.00

Molecular weight for FeO = 71.85

Molecular weight for Fe2O3 = 79.85

From this basic info you can calculate any conversion factor you want, depending on what analysis data you have available.

Fe wt% => FeO wt% : Fe x 71.85/55.85

Fe2O3 wt% => FeO wt% : Fe2O3 x 71.85 / 79.85 or Fe2O3 x 0.8998

D. M. Evans is correct, the problem is that you have to know in advance the Fe2+/Fe3+ ratio, which you don't, or make some reasonable assumptions about it.

Dear Reda Chatiby

You have not provided us with a clear question. If your analyses are expressed as Fe2O3 (total Fe as Fe2O3), you can readily convert that to FeO (total) by using the factors given by D.M. Evans. But if the question involves splitting Fe2O3 (total Fe as Fe2O3) into its components of actual FeO and actual Fe2O3, you cannot do it. You need a different type of analysis. Typically XRF analysis provides either Fe2O3(total) or FeO(total). You need a different type of analysis, e.g. wet chemical.

Your analysis probably reflects Fe2O3 - assuming XRF analysis, when powders are fused in a flux at typically ~1000oC all Fe in the sample is oxidised to Fe3+ and expressed as Fe2O3. You could make a guesstimate from the mineralogy of your BIF with regard to the ratio of magnetite to hematite. If all magnetite, one has a ratio of 1:1 FeO:Fe2O3 and hematite totally Fe2O3. From the mineral proportions an estimate can be made to allocate the Fe2O3 of analysis into Fe2O3 and FeO as separate components.

Geoff Grantham; what is the point of estimating FeO and Fe2O3, when all of the other components are analysed accurately? Even obtaining real values of FeO and Fe2O3 might not be very meaningful if the BIF is weathered, unless the analysis is for estimating mine grades.

To estimate the Fe(II) content in samples, it is necessary to use special analytic techniques. For example, titrimetric analysis method. Mössbauer spectroscopy is also very effective, but this is not a routine method

Dear Reda,

In my experience with BIF in Brazil, this procedure did not work, because it is very common to have a hematite crystal that still has a magnetite core and in this case the hematite (martite) is magnetic. That is, knowing the FeO content does not help much.

In this case it was necessary to physically determine the content of magnetic and non-magnetic concentrate. We calculated the iron content in Fe2O3.

Best Regards

The approach used by D, M Evans is correct and adopted to solve the problem