Susceptibility ,measurements can be done with a Kappameter in the field and laboratory. The magnetic susceptibility depends on minerals in which the iron is contained. As no correlation is observed it means that the iron is mostly concentrated in paramagnetic minerals. The majority of minerals which do not accommodate iron in their lattice are diamagnetic yielding a negative moderate susceptibility, e.g., calcite and quartz, which are the most common constituents of many sedimentary rocks. By contrast, Fe-bearing paramagnetic minerals give a positive read-out which can be higher by several orders of magnitude than those obtained for diamagnetic minerals. Siderite, ankerite and some Fe-bearing phyllosilicates pertain to these minerals. Only a fraction of these minerals are ferrimagnetic, the most well-known of which are magnetite [Fe3O4], maghemite [γ-Fe2O3], ferroxyhyte [δ-FeOOH] and pyrrhotite [Fe7S8] which can also appear in sedimentary rocks. Another group of Fe-bearing minerals also quite common to sedimentary rocks differ from the afore-mentioned oxidic Fe minerals by their antiferromagnetic order such as hematite [α-Fe2O3], ilmenite [FeTiO3] and goethite [α-FeOOH].

H.G.Dill

@Harald G.Dill

Dear Sir, Thank you for your valuable suggestions. But I wish to know how can I distinguish all positive magnetic susceptibility values. Like if it is negative then I can easily say it's diamagnetic but if the value is positive, suppose I got 2 values of 2 different samples like 15.8×10^-8 and 289×10^-8(m3/kg). then how can I distinguish which one is para or Ferri or ferromagnetic. Kindly suggest

Hello Subhrajit,

Perhaps you can try backing it out from their Currie temperatures. Ferromagnetic minerals will have a higher Currie temperature than Ferrimagnetic minerals. Additionally ferromagnetic minerals will have stronger fields, can you measure this?

If your samples are a compilation of minerals both ferromagnetic and ferrimagnetic. I do not believe there is a way to parse out their percentages by susceptibility alone, unless you had a large data set and some well established parameters. Alternatively, you can make petrographic slides to determine which minerals you have, this will shed light on their magnetic behaviors.

I hope this is useful.

Jonathon

Dear Dr. Das,

I always prefer a multidisciplinary approach , e.g., geophysical methods vs. mineralogy to a stand-alone geophysical one. Too often you end up in a dead-end street. Our Kappameter measurements where backed by mineralogical methods based on XRD and heavy mineral analysis using thin sections and SEM/EDX-WDX.

H.G.Dill

Susceptibility data gives idea about magnetic concentration and not identify magnetic minerals. For that you can do as rightly suggested by Jonathon Waian.