Estimation of Fe in Magnetite

An important distinction in Fe exploration is to determine in which mineral phases the Fe is hosted, rather than just the total Fe content. Significant portions of the total Fe in a magnetite deposit can be hosted in hematite or pyrrhotite, and of course silicate minerals. A Swedish iron oxide-apatite deposit, explored by Nordic Iron Ore, contains both magnetite and hematite. Drill cores from this project were analysed with Minalyzer CS. Magnetite content has been measured with a Satmagan. Some samples display higher Fe concentrations than can be explained by their magnetism. However, total V content correlates relatively well with the magnetite content.

Client Nordic Iron Ore
Services Drill Core analysis
Year 2017

Taking the highest V value and assuming that all V is hosted in magnetite, gives a V content in magnetite of 0.2 %. Using this ratio, the Fe in magnetite can be estimated.

The estimated amount of Fe in magnetite by both methods was subtracted from the total Fe reported by Minalyzer CS. In a downcore comparison, the Satmagan and Minalyzer CS data both identify two zones of mixed magnetite and hematite ore.

In this case the preferred partitioning of V into magnetite, and its relatively stable concentration, allowed a qualitative and preliminary discrimination of the Fe hosted in magnetite and other minerals (mainly hematite). This general principle can be applied to different types of commodity, as long as the mineralogy is not too complicated.

“The data gathered by Minalyze has proven extremely useful indeed for NIO. The correlations drawn from the concentration of V within the magnetite/hematite has helped identify distinct zones of ore within our deposits enabling correct classification of differing ore types. The quick turnaround time from core drilled, delivery to, scanning and returned to NIO and the almost instantaneous generation of assay results quickly sorts the wheat from the chaff. This reduces the wait time from a few weeks for assay results from a traditional lab to days, enabling a fully dynamic drilling programme. The additional features such as scanning of density, magnetic susceptibility, geotechnical features and production of high resolution core photographs saves valuable time, effort and funds. This is the future.”

Michael Setter – Senior Geologist – Nordic Iron Ore