Mineralogical and Chemical Characterization of Disseminated Low-Grade Sudanese Chromite Ore in Gedarif State at Umm Saqata-Qala Elnahal Mahmoud Motasim Hassan Al-Tigani1*, Abdelshakour Awdekarim Mohamed2 and Ahmed Abdullah Sadeek Seifelnasr3 1Department of Mining Engineering, Faculty of Engineering, Omdurman Islamic University, Khartoum, Sudan 2Department of Chemical Engineering, Faculty of Engineering, University of Khartoum, Khartoum, Sudan 3Department of Mining Engineering, Faculty of Petroleum and Mining, Suez Canal University, Suez, Egypt *Corresponding author: Mahmoud Motasim Hassan Al-Tigani, Department of Mining Engineering, Faculty of Engineering Sciences, Omdurman Islamic University, Khartoum, Sudan, Tel: 00249960579034; E-mail: Mahmoudmotasim2018@hotmail.com Rec date: October 07, 2019; Acc date: November 04, 2019; Pub date: November 11, 2019 Copyright: © 2019 Al-Tigani MMH, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract This study was carried out on the low-grade chromite, Gedarif state, Sudan, at Umm SaqataQala Elnahal to achieve full characterization for the ore via Microscopic studies for the polish section samples, X-ray diffraction analysis (XRD), X-ray Fluorescence Analysis (XRF), Scanning electron microscopic with Energy Dispersive X-ray Spectroscopy (SEM-EDX), and physical properties tests. Microscopic study revealed that the liberation size of chromite mineral is in the range (0.30-0.05) mm. also the X-ray diffraction, X-ray fluorescence and scanning electron microscope with the Energy Dispersive X-ray analysis showed that main gangue of the ore is mineral silicates as Antigorite and contains 21.58-19.60% Cr2O3. The physical tests (saturated density and dry density) demonstrated that ore has low density in range 2.54-2.38 g/cm3 because it is low grade chromite ore, this can be attributed to the dominating mineral silicate (waste) which associated with chromite mineral. Keywords: Characterization; Low-grade chromite; Microscopic; SEM; EDX; XRF; XRD Introduction Chromium (Cr) is one of the world's most strategic and critical materials having a wide range of uses in the metals and chemical industries. Alloys containing Cr enhance metal resistance to impact, corrosion, and oxidation. In addition, Cr is used primarily in stainless steel and noniron alloy production for plating metals, development of pigments, leather processing, and production of catalysts, surface treatments, and in refractories [1]. Characterization of the low-grade ore of minerals is very important because it considered the key of selection suitable method for treatment or processing (upgrading) via physical methods, chemical methods and physiochemical methods. Characterization for low grade of minerals widely obtained by using microscopic studies for thin or polish sections samples, X-ray diffraction (XRD) Analysis, XFluorescence Analysis, Scanning electron Microscopic studies, Energy Dispersive X-ray Spectroscopy (EDX), and physical properties tests (Natural density, saturated density, etc.). Chromite ore deposits in Sudan mainly occur in the Ingassana Hills in the Blue Nile region. Other occurrences have been reported at Hammissana, Sol Hamid in the Northern Red Sea Hills, and the Nuba Mountains in Southern Kordofan, Jabal Rahib Northwest Sudan, and Jabal El-Tawil in Central Butana in Southern Sudan in Umm SaqtaQala Elnahal [2]. The present investigated area covers part of Qala En Nahal and Umm Saqata area in the south-western part of Gedarif State near the border line between the Sudan and Ethiopia. The area investigated is about 2450 km2 bounded by Long. 34o 35` and 35o13`E and Lat. 13o18` and 13o43`N Figure 1, the reserves of this study exceed 6,00,000 tons, some occurrence are not estimated [2,3]. Low grade chromite of Ingassana Hills was characterized by wet chemical analysis and microscopic studies for thin and polish section. Wet chemical analysis revealed that ore contains 24.9% Cr2O3; 8.6% Fe2O3; SiO2% 24.2; 13.1% MgO; 0.02% CaO; Cr/Fe 2.9, this result explained that mainly gunge are silicate and it has low iron to chromium ratio. However, the examination of thin and polished sections revealed that the main minerals were chromite [(Fe,Mg)O. (Al,Fe,Cr)2O3] and serpentine [(Mg,Fe)3Si2O5 (OH)4] [4]. Microscopic studies Thin and polish section prepare from bulk samples and then study by using microscope (ore microscope, reflective microscope, nuclear microscope) to get information about the topography of minerals also to estimate the grain size and liberation size for desire mineral widely chromite mineral appears in Euhedral chromite (pure grey) in magnetite (brownish grey), hematite (light grey lamellae) or Anhedral chromite (medium grey) between silicates (dark grey), small pyrite grains (yellow) [5]. X-ray diffraction (XRD) X-ray diffraction is a versatile analytical technique for examining crystalline solids, which include ceramics, metals, electronic materials, geological material, organic, and polymers. These materials may be powders or irregular shapes. X-ray diffractometers fall broadly into two classes: single-crystal and powder. Single-crystal diffractometers are most often used to determine the molecular of new materials. Powder diffractometers are mostly and routinely used for phase identification and quantitative phase analysis in mineral processing applications [6]. Jo ur na l o f E nv iro nme ntal Analytical Chem istry ISSN: 2380-2391 Journal of Environmental Analytical Chemistry Al-Tigani et al., J Environ Anal Chem 2019, 6:3 Research Article Open Access J Environ Anal Chem, an open access journal ISSN: 2380-2391 Volume 6 • Issue 3 • 1000261 Figure 1: Chromite locations in Qala EL-Nahl and Umm Saqata. X-Ray fluorescence analysis (XRF) X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental and chemical analysis, particularly in the investigation of metals, rocks, glass, ceramics and building materials. In minerals processing applications X-ray fluorescence was used to evaluate the elements and mineral oxide in the ore [7,8]. Scanning electron microscopy (SEM) with the energy dispersive X-ray spectroscopy (EDX) Scanning Electron Microscope with the Energy Dispersive X-ray Spectroscopy is commonly used to get information about the sample surface, topography and composition. A scanning electron microscope (SEM) produces images of a sample by scanning it with a focused beam of high energy electrons. The electron beam is scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image [9]. Materials and Methods Materials Chromite ore sample: Low grade disseminated chromite ore was collected from different interval locations through the lenses body in Umm Saqata. The samples were lumpy with a total collection weight about 100 kg, then were thoroughly mixed to be homogenous. Finally, thin and polish sections were made for mineralogical analysis from the lumpy samples. Methods Preparation of samples: A representative sample of the lumpy samples was taken (about 30 kg) with particle size of 10 cm. The sample was crushed by jaw crusher to -2 cm then by roll crusher to -2 mm in a closed circuit (Figure 2). Figure 2: Sample preparation flow sheet. Finally, a representative sample was taken for characterization by using coning and quartering method (Figure 3). Figure 3: A representative sample for characterization. Citation: Al-Tigani MMH, Mohamed AA, Seifelnasr AA (2019) Mineralogical and Chemical Characterization of Disseminated Low-Grade Sudanese Chromite Ore in Gedarif State at Umm Saqta-Qala Elnahal. J Environ Anal Chem 6: 261. Page 2 of 5 J Environ Anal Chem, an open access journal ISSN: 2380-2391 Volume 6 • Issue 3 • 1000261 Results and Discussion Microscopic studies Plate 1, Plate 2, Plate 3, and Plate 4 show that most of the rock matrix composed of the gangue minerals mainly (Antigorite) about 70% of the rock matrix. About 12% of magnetite is replaced by hematite, and most of the rest are chromite and ferrochrome 6% of the matrix, with minor amounts of native copper, Azurite, Malachite, Chalcopyrite, and Limonite. Polish section plates revealed that chromite and magnetite particles appeared in euhedral shape. However, the liberation size of chromite was found in the range between (0.3-0.5) mm which will oblige that the size of the ground product should be between (-212+75) microns. Plate 1: Chromite and magnetite under 20x. Plate 2: Native copper and chalcopyrite under 20x. Plate 3: Hematite, antigorite, and small crystal of azurite 20x. Plate 4: Relict of disseminated texture of chromite under 4x. X-ray diffraction (XRD) Figure 4 reveals that chromium element was located in spinel composition (AB2O4) with Ca and Fe (Chromtite CaCrO4, Chromite FeCr2O4), as well as the Sample contained Antigorite (MgO.SiO2.H2O), Magnetite (Fe3O4), and Chabazite (Ca1.85 (Al3.7Si8.3O24)). Figure 5 shows that the highest peaks are the chromtite and antigorite indicating these two mineral are of high concentration. Citation: Al-Tigani MMH, Mohamed AA, Seifelnasr AA (2019) Mineralogical and Chemical Characterization of Disseminated Low-Grade Sudanese Chromite Ore in Gedarif State at Umm Saqta-Qala Elnahal. J Environ Anal Chem 6: 261. Page 3 of 5 J Environ Anal Chem, an open access journal ISSN: 2380-2391 Volume 6 • Issue 3 • 1000261 Figure 4: Chemical composition of the mineral phases. Figure 5: Pattern of the mineral phases. SEM-EDX study Figure 6 showed the pattern of the elements in EDX result. These elements are (Cr, Fe, Al, Si, Mg) and indicated to the presence of (Cr2O3, Fe3O4, Al2O3, SiO2, MgO) respectively. These oxide minerals are considering the main content of the Chromtite, Magnetite, Antigorite and Chabazite minerals. Figure 6: The pattern of the elements in EDX. More over Figure 6 demonstrated that the Cr, Fe, and O elements existed in one peak that indicates to the spinel composition. Table 1 shows the percentage of the presence elements and their corresponding oxides. Element Weight (%) Mineral Oxide Weight (%) Cr 13.37 Cr2O3 19.6 Fe 5.34 Fe2O3 7.628 Mg 16.11 MgO 26.85 Al 3.97 Al2O3 7.6918 Si 10.66 SiO2 22.84 Table 1: Chemical analysis for the elements by EDX. Plate 5 showed that the silicate minerals have a pastel grey color whereas chromite and Magnetite minerals have dark grey color. Plate 5: Chromite, magnetite, and silicates in Scanning Electron Microscope (SEM) image. X-Ray fluorescence analysis (XRF) Table 2 shows the chemical analysis of the head sample (-2 mm) via XRF and it revealed that the silicate mineral is mainly gangue in the ore. Oxide Cr2O3 Fe2O3 SiO2 Al2O3 MgO % 21.5 11.8 32.61 4.608 28.09 Table 2: Chemical analysis of the head sample. Physical properties Table 3 shows the calculated densities of the low grade chromite. It can be concluded that the ore is low density. This result can be attributed to the dominating mineral silicate (waste) which associated with chromite mineral. Citation: Al-Tigani MMH, Mohamed AA, Seifelnasr AA (2019) Mineralogical and Chemical Characterization of Disseminated Low-Grade Sudanese Chromite Ore in Gedarif State at Umm Saqta-Qala Elnahal. J Environ Anal Chem 6: 261. Page 4 of 5 J Environ Anal Chem, an open access journal ISSN: 2380-2391 Volume 6 • Issue 3 • 1000261 Sample Name Natural densityg/cm3 Dry density g/cm3 Saturated density g/cm3 SCR 1 2.43 2.41 2.56 SCR 2 2.28 2.26 2.46 SCR 3 2.41 2.41 2.56 SCR 4 2.4 2.39 2.53 SCR 5 2.38 2.36 2.58 Average 2.38 2.36 2.54 Table 3: The densities of low grade chromite ore. Conclusion The most of gangue mineral associated with tested chromite ore are silicates as the Antigorite mineral and other minerals (magnetite and chabazite). Microscopic investigations indicated that this ore was a low grade disseminated chromite ore and the liberation size in the range of (0.3-0.05 mm). X-ray diffraction administrated that the chromium element was located in spinel composition (AB2O4) with Ca and Fe (chromtite CaCrO4, chromite FeCr2O4). Moreover, the Sample contained Antigorite (MgO.SiO2.H2O), Magnetite (Fe3O4), and Chabazite (Ca1.85 (Al3.7Si8.3O24)). Physical properties tests (Natural density, saturated density, and dry density) revealed that the ore of this research has low density and that is attributed to the dominating mineral silicate (waste) which associated with chromite mineral. X-ray Florence's revealed that the ore of chromite is low grade contained 21.58% Cr2O3 and the silicate mineral is mainly gangue in the ore. Scanning electron microscope (SEM) with Scanning Electron Microscope with the Energy Dispersive X-ray Spectroscopy revealed the topography of the ore is mineral silicate witch is appeared in a pastel grey. However, the elements witch are appeared (Cr, Fe, Al, Si, Mg) and indicated to the presence of (Cr2O3, Fe3O4, Al2O3, SiO2, MgO). Also it approved there are no precious metal in this ore. Acknowledgment The authors are grateful to General of Geological Research Authority of Sudan (GRAS) in Gadaref State, for logistic support during the fieldwork. Also the acknowledgment is going deeply to Eng. W. Osaman, Quality Control Department in Kush for Mining Co-ltd for financial support. Moreover, the authors thank Eng. I. Mubarak, University of Khartoum, Faculty of Engineering, Chemical Engineering Department for supporting in samples analysis. References 1. Guertin J, Jacobs JA, Avakian CP, Handbook CV (2005) Independent Environmental Technical Evaluation Group (IETEG). 2. 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Reed SJB (2005) Electron microprobe analysis and scanning electron microscopy in geology. Cambridge University Press, USA. Citation: Al-Tigani MMH, Mohamed AA, Seifelnasr AA (2019) Mineralogical and Chemical Characterization of Disseminated Low-Grade Sudanese Chromite Ore in Gedarif State at Umm Saqta-Qala Elnahal. J Environ Anal Chem 6: 261. Page 5 of 5 J Environ Anal Chem, an open access journal ISSN: 2380-2391 Volume 6 • Issue 3 •