## 2 Scanning Electron Microscopy and Mineral Characterization
### Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN)  
Traditional mineral analysis based on microscopy cannot provide the needed data because of the absence of quantitative information and the very small size of the particles of interest. QEMSCAN technology, initially termed QEM*SEM, demonstrated the potential to revolutionize automated mineralogy [124]. In a mold, the particulate mineral sample is mixed with epoxy resin, and the sample surface is prepared using cutting, polishing, and carbon coating. The sample is scanned using SEM in backscatter mode, enabling the differentiation of particles from the background. After the identification of particles on the resin block, their composition is systematically mapped using EDS. In contrast to the most modern SEMs coupled with single EDX, QEMSCAN possesses the attribute  
Figure 7: (**a**) SEM-MLA measurement of a hydrothermally overprinted alkali plutonite showing the backscattered electron (BSE) image and (**b**) color-coded, grouped, and classified presentation of the frame presented in (**a**) [85]. CC-BY. of having multiple EDXs at the same time, enabling rapid quantitative mineralogy. The acquired EDX signals are then compared with reference known materials in the database and assigned a mineral name or to a chemical compositional grouping. With this process, the mineralogy of the sample can be determined by particle-by-particle analysis [124]. QEMSCAN locates the particles using a BSE signal, while identifying the mineral by an EDS signal. It can be compared to SEM-MLA, which makes more use of the BSE signal than EDS for identifying the mineral. SEM-MLA works very well for bright phases (such as platinum group element minerals). Among SEM-EDS techniques, QEMSCAN is one of the most widely used and offers quantitative characterization of minerals, ores, and other mineralogical compounds [125; 126; 127; 128; 129]. QEMSCAN is usually used in conjunction with other analytical techniques, such as electron probe microanalysis (EPMA) and X-ray diffraction (XRD), as shown in Table 1[130]. Figure 8 indicates the use of QEMSCAN for identifying the mineral distribution of four samples [130]. It shows the presence of geothite, quartz, clay, limonite, and other silicate minerals. The above-described four analytical techniques are distinct but complement each other in comprehensive mineralogical analysis. High-resolution images are provided by SEM, elemental composition analysis is provided by EDS, and SEM with automated mineralogy involves a thorough mineral characterization. Most SEMs with automated mineralogy equipment incorporate EDS, where software utilization provides objective and quick mineral characterization and other analytical results. QEMSCAN is a specific instance of the broader concept of automated mineralogy, which represents a specific system and brand used for comprehensive mineral characterization. MLA systems are used in geology, mining, and mineral analyses for ore processing and beneficiation, as they provide insight into the degree of liberation of valuable minerals from the host rock. Combining these techniques offers constructive value to mineral characterization and the analysis process by not only providing high-resolution surface images but also offering the elemental composition of the sample, the degree of liberation of minerals, and saving time in determining the presence of valuable minerals present in ores. In short, SEM is a powerful technique for the characterization and analysis of various minerals [131; 132; 133]. Mineral characterization is usually carried out with more than one technique for clear identification and quantification. Therefore, SEM analysis for mineral characterization is accompanied by several other analytical techniques, as mentioned in Table 2, which have been applied in some recent publications.