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Iron ore analysis

Iron ore

Iron is the fourth most abundant element in the Earth's crust, but economic concentrations are dominated by comparatively rare iron oxide forms; magnetite (Fe3O4), hematite (Fe2O3), goethite (FeOH), limonite (FeO(OH)nH2O) and siderite (FeCO3). The mineralogy of iron ore impacts its commercial value and how it is processed. Identifying iron mineralogy along with gangue minerals which impact the beneficiation are an essential part of iron ore analysis.

Minério de ferro

Multi-element analysis

Most iron ore is used to manufacture steel which is impacted by the concentration of other elements present in the ore as they affect steel quality. For this reason, standard iron ore analysis is a multi-element analysis which reports the major rock forming elements and a suite of trace elements. .

Iron ore analysis

Iron ore samples are fused with a lithium borate fusion containing an oxidising agent followed by XRF instrument analysis for major rock forming elements and selected trace element concentrations. Results can be reported as either un-normalised or normalised to 100% (excluding the LOI). Loss on Ignition (LOI) is always carried out as part of the multi-element analysis.

Code Analytes & Ranges (%) Description
ME_XRF21u
(unnormalised)

ME_XRF21n
(normalised)

0.7g sample		 Al2O3 0.01-100 K2O 0.001-6.3 Sn 0.001-1.5 Fused disc XRF.
LOI included as part
of this procedure.
As 0.001-1.5 MgO 0.01-40 Sr 0.001-1.5
Ba 0.001-10 Mn 0.001-25 TiO2 0.01-30
CaO 0.01-40 Na2O 0.005-8 V 0.001-5
Cl 0.001-6 Ni 0.001-8 Zn 0.001-1.5
Co 0.001-5 P 0.001-10 Zr 0.001-1
Cr2O3 0.001-10 Pb 0.001-2 Total 0.01-110
Cu 0.001-1.5 S 0.001-5
Fe 0.01-75 SiO2 0.01-100
OA-GRA05x
ME-GRA05 		Loss on Ignition.
1g sample 		Furnace or
Thermo-gravimetric Analyser (TGA).

Loss on ignition (LOI)

ALS offers a range of LOI methods by either furnace or Thermogravimetric Analyser (TGA). A variety of temperatures are available, either at a single temperature or range of temperatures run consecutively to fully characterise the volatile component of samples. To identify only the unbound water in a sample heating is limited to 105ᵒC whereas if water bound in crystals and other volatile components are required, heating is typically increased to 1000ᵒC.

Thermogravimetric analyser (TGA)

Thermogravimetric analysis is when the mass of a sample is measured with time and temperature changes. Measurements can be customised as required to fully characterise volatile components, especially for samples with variable amount of water bound in minerals.

Method code Analyte Description
OA-GRA10 H2O (moisture) Gravimetric procedure after drying at 105ᵒC for 2 hours
OA-GRA11 H2O (moisture) Gravimetric procedure after drying at 105ᵒC for 24 hours
OA-IR05 H2O (moisture) Infrared detection system measurement of water with heating to 110ᵒC
OA-IR06 H2O and crystalline bound water Infrared detection system measurement of water with heating to 110ᵒC
OA-GRA05xf Loss on Ignition at 500ᵒC A sample is pre-dried at 105ᵒC before heating to 500ᵒC to determine loss on ignition
OA-GRA05 Loss on Ignition at 1000ᵒC A sample is heated to 1000ᵒC as received to determine unbound water plus bound volatile component in total.

Davis tube recovery (DTR)

Davis tube recovery (DTR) is a lab-scale version of the ore beneficiation process that separates magnetic from non-magnetic fractions. After crushing and pulverising, samples are placed in an angled tube on the DTR instrument and agitated while passing water through the tube. The tube is positioned between the poles of a strong electromagnet which prevents magnetic particles from washing through the tube with the non-magnetic particles.

Pulverisation specifications

The separation of magnetic from non-magnetic particles is affected by the pulverisation size specifications – the finer the grinding, the more magnetic fraction will be recovered as it will be freed from non magnetic gangue minerals which would increase the weight to magnetic strength. Initial test work may be required to identify the optimum protocol for a new ore deposit to ensure the method approximates the mine scale beneficiation.

Code Description
DTR_PREP Multi-stage sieving and pulverising.
DTR_FeRec DTR iron recovery.
ME_XRF21h/c/t XRF analysis on various DTR fractions (head, concentrate, tailing). 0.7g sample each
OA-GRA05xh/xc/xt Loss on Ignition reported as part of this method.
Fe-VOL05 Ferrous iron by titration (FeO; 0.01-100%). 1g sample
MAG-DTR Recovery of magnetic fraction by DTR
*Note: These methods are not suitable for samples with base or precious metals mineralisation.

Magnetic susceptibility

Magnetic susceptibility (Mag-Sus) is a dimensionless measurement of how magnetised a material will become in a magnetic field. The measurement is functionally the proportion of sample that is magnetic. This is often an estimation of magnetite content but other ferromagnetic minerals, like maghemite and ilmenite (FeTiO3), are also magnetic and will be included in the total.

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Iron Ore at Mineralogy

Frequently asked questions

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Physical tests

Characterising bulk density/specific gravity of ore and waste is an essential part of any deposit estimation process.

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Iron ore mineralogy

ALS offers QEMSCAN®, MLA, X-ray diffraction, HyLogging™ and optical microscopy to understand the mineralogical variability within a deposit.

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