Introduction

Steel is a fundamental material used in many industries, including automotive, shipbuilding, and construction. Iron ore used as the primary raw material for steel is composed of iron-bearing minerals and gangue minerals, which are economically non-valuable minerals associated with ore.

In recent years, high‑grade iron ore with high iron content has been depleted. As a result, the use of lower‑grade ore has grown, making beneficiation more important for improving ore grade.

The beneficiation method depends strongly on the mineralogical composition of the ore. However, chemical analysis cannot distinguish between types of iron-bearing minerals and gangue minerals. Furthermore, it cannot properly evaluate the mineralogical composition. Thus, it is difficult to optimize the beneficiation process based solely on chemical analysis.

X‑ray diffraction (XRD) can directly identify and quantify mineral phases. Therefore, it is an effective technique for evaluating the mineralogical composition of iron ore. This application note presents examples of phase identification and quantitative analysis of iron ore using XRD.

Measurement and analysis example

Two iron ore standard reference materials, NBS 692 (Labrador) and NBS 693 (Nimba), were measured using the MiniFlex benchtop X-ray diffractometer. These materials originate from different regions.

Iron ore has high iron content. Therefore, measurements performed with a Cu tube induce intense iron fluorescence. This fluorescence results in a high background intensity, making it difficult to observe low‑intensity diffraction peaks. In contrast, a Co tube produces less iron fluorescence, resulting in a lower background intensity compared with a Cu tube. Therefore, a Co tube was used in this example, and high‑quality diffraction patterns were obtained in approximately 10 minutes.

Figure 1 shows the results of phase identification. Hematite, magnetite, and goethite were identified as iron-bearing minerals. Quartz, gibbsite, and dickite were identified as gangue minerals. Table 1 shows the results of quantitative analysis by the Rietveld method. The weight fractions of these minerals were found to vary depending on the ore deposit regions.

Figure 1:  Results of phase identification for NBS692 and NBS693
※The vertical axis uses offset notation. 

Table1：Weight fractions of each crystalline phase in NBS692 and NBS693

Recommended equipment and software

• MiniFlex benchtop X-ray diffractometer
• MiniFlex XpC compact X-ray diffractometer
• SmartLab SE or SmartLab automated multipurpose X-ray diffractometers
• SmartLab Studio II integrated X-ray analysis software (Powder XRD Plugin)