• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.227-239
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• 2021

A practical and effective method of X-ray powder diffraction analysis was investigated for quantitative analysis of the mineral content of natural samples. Sample mounting experiments were conducted to select the best randomly oriented powder sample mount. A comparative experiment was also made between a reference intensity ratio (RIR) method, which compares a single peak intensity with standard material, and the Rietveld method, which calculates a full X-ray diffraction pattern, to search for the effective method of mineral quantification. In addition, samples containing amorphous minerals were quantitatively analyzed by the Rietveld method and the efficiency was reviewed. As a result of the study, the optimal random orientation could be reached by the side mounting method. The Rietveld method using the full pattern of X-ray diffraction was more suitable for mineral quantitative analysis, rather than the RIR method using a specific peak. However, either method could depend on the analyst's experience in addition to analytical technique. Moreover, amorphous minerals can be quantitatively analyzed by the Rietveld method, and the analysis results make the geological analysis possible.

• Journal of the Mineralogical Society of Korea
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• v.22 no.2
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• pp.115-127
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• 2009

Mineral quantification was performed on sediments of the Ulleung basin by X-ray powder diffraction and the computer software based on Rietveld quantification method. The sediments are dominated by amorphous opal-A with quartz, feldspars, micas, clays, calcite, and pyrite. The opal-A shows iterative variation in abundance with increasing burial depth. In addition, the relative abundance of opal-A is coincident with abundance of organic carbon contents, indicating that the Ulleung sediment consists mostly of amorphous silica derived from organism in the pelagic environment. Upward increase in the abundance of opal-A is markedly shown in the cores located in the slope region. On the other hand, there is a distinct tendency that the abundance of calcite is inversely proportional to that of opal-A. This indicates that the abundance of opal-A increases during the rise of sea level. Also, the fall of sea level lowers the abundance of opal-A.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.4
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• pp.431-445
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• 2022

A quantitative phase analysis method of X-ray powder diffraction was studied to determine the mineral content of clay-rich rocks practically as well as effectively. For quantitative X-ray powder diffraction analysis of the clay-rich rocks, it is necessary to prepare whole-rock powder samples with a random orientation by side mounting method. In addition, for the identification of the clay minerals in the rock, it is required to prepare an oriented mount specimen with a clay particle size of 2 ㎛ or less, ethylene glycol treatment, and heat treatment. RIR (reference intensity ratio) and Rietveld method were used for the quantitative analysis of the clay-rich rocks. It was possible to obtain the total clay and the non-clay minerals contents from the whole-rock X-ray diffraction profiles using the RIR values. In addition, it was possible to calculate the relative content of each clay mineral from the oriented X-ray diffraction profiles of the clay particle size and assign it to the total clay. In the Rietveld method of whole-rock X-ray diffraction, effective quantitative values were obtained from the Rietveld diffraction patterns excluded the region of less than 10 degrees (2θ). Similar quantitative values were shown in not only the RIR but the Rietveld methods. Therefore, the analysis results indicate a possibility of a routine quantitative analysis of clay-rich rocks in the laboratory. However, quantitative analysis of clay minerals is still a challenge because there are numerous varieties of clay minerals with different chemical and structural characteristics.

• Journal of the Mineralogical Society of Korea
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• v.26 no.1
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• pp.27-34
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• 2013

X-ray powder diffraction is one of the most powerful techniques for qualitative and quantitative analysis of crystalline compounds. Thus, there exist a number of different methods for quantifying mineral mixtures using X-ray diffraction pattern. We present here the use of Rietveld and PONKCS (partial or no known crystal structure) methods for quantification of amorphous and crystallized mineral phases in synthetic mixtures of standard minerals (amorphous silica, quartz, mullite and corundum). Pawley phase model of amorphous silica was successfully built from the pattern of 100 wt% amorphous silica and internal standard-spiked samples by PONKCS approach. The average of absolute bias for quantities of amorphous silica was 1.85 wt%. The larger bias observed for lower quantities of amorphous silica is probably explained by low intensities of diffraction pattern. Averages of absolute bias for minerals were 0.53 wt% for quartz, 0.87 wt% for mullite and 0.57 wt% for corundum, respectively. The PONKCS approach achieved improved quantitative results compared with classical Rietveld method by using an internal standard.

• Economic and Environmental Geology
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• v.50 no.1
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• pp.15-26
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• 2017

Advanced argillic, argillic, and phyllic zones are the most important alteration patterns to predict the hidden ore body during exploration of hydrothermal deposits. We examined the quantitative relationship between the spectral absorption characteristics and the mineral content of the synthetic mixtures such as alunite-kaolinite and illite-kaolinite using short wavelength infrared (SWIR) spectroscopy. In the alunite-kaolinite mixtures, the spectral absorption characteristics of the alunite was highly correlated with the Hull quotient reflectance(0.99) and the kaolinite had the highest correlation with the Gaussian peak(0.92). Illite-kaolinite mixtures are essential for Gaussian deconvolution because of the overlap of absorption region. Illite and kaolinite mixtures indicate the high correlation of 0.93 and 0.98, respectively. The error ranges in the alunite-kaolinite(8%) and illite-kaolinite mixtures(5%) derived from SWIR were smaller than the ones(29% and 26%) obtained from X-ray diffraction(Rietveld) analysis. These results show that SWIR spectroscopic analysis is more reliable than XRD Rietveld analysis in terms of quantification of allowed minerals.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1171-1171
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• 2001

Quantitative analysis is an important requirement in exploration, mining and processing of minerals. There is an increasing need for the use of quantitative mineralogical data to assist with bore hole logging, deposit delineation, grade control, feed to processing plants and monitoring of solid process residues. Quantitative analysis using X-Ray Powder Diffraction (XRD) requires fine grinding and the addition of a reference material, or the application of Rietveld analysis to XRD patterns to provide accurate analysis of the suite of minerals present. Whilst accurate quantitative data can be obtained in this manner, the method is time consuming and limited to the laboratory. Mid infrared when combined with multivariant analysis has also been used for quantitative analysis. However, factors such as the absorption coefficients and refractive index of the minerals requires special sample preparation and dilution in a dispersive medium, such as KBr to minimize distortion of spectral features. In contrast, the lower intensity of the overtones and combinations of the fundamental vibrations in the near infrared allow direct measurement of virtually any solid without special sample preparation or dilution. Thus Near Infrared Spectroscopy (NIR) has found application for quantitative on-line/in line analysis and control in a range of processing applications which include, moisture control in clay and textile processing, fermentation processes, wheat analysis, gasoline analysis and chemicals and polymers. It is developing rapidly in the mineral exploration industry and has been underpinned by the development of portable NIR spectrometers and spectral libraries of a wide range of minerals. For example, iron ores have been identified and characterized in terms of the individual mineral components using field spectrometers. Data acquisition time of NIR field instruments is of the order of seconds and sample preparation is minimal. Consequently these types of spectrometers have great potential for in-line or on-line application in the minerals industry. To demonstrate the applicability of NIR field spectroscopy for quantitative analysis of minerals, a specific example on the quantification of lateritic bauxites will be presented. It has been shown that the application of Partial Least Squares regression analysis (PLS) to the NIR spectra can be used to quantify chemistry and mineralogy in a range of lateritic bauxites. Important, issues such as sampling, precision, repeatability, and replication which influence the results will be discussed.

• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.329-344
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• 2002

Mineralogical and chemical characterization of some domestic bentonites, such as quantitative XRD analysis, chemical leaching experiments, pH and CEC determinations, were done without any separation procedures to understand their relationships among mineral composition, characteristics, and cation exchange properties. XRD quantification results based on Rietveld method reveal that the bentonites contain totally more than 25 wt% of impurities, such as zeolites, opal-CT, and feldspars, in addition to montmorillonite ranging 30～75 wt%. Cation exchange properties of the zeolitic bentonites are deeply affected by the content of zeolites identified as clinoptilolite-heulandite series. Clinoptilolite is common in the silicic bentonites with lighter color. and occurs closely in association with opal-CT. Ca is mostly the dominant exchangeable cation, but some zeolitic bentonites have K as a major exchangeable cation, The values of cation exchange capacity (CEC) determined by Methylene Blue method are comparatively low and have roughly a linear relationship with the montmorillonite content of the bentonite, though the correlated data tend to be rather dispersed. Compared to this, the CEC determined by Ammonium Acetate method, i.e.‘Total CEC’, has much higher values (50～115 meq/100 g). The differences between those CEC values are much greater in zeolitic bentonites, which obviously indicates the CEC increase affected by zeolite. Other impurities such as opal-CT and feldspars seem to affect insignificantly on the CEC of bentonites. When dispersed in distilled water, the pH of bentonites roughly tends to increase up to 9.3 with increasing the alkali abundance, especially Na, in exchangeable cation composition. However, some bentonites exhibit lower pH (5～6) so as to regard as ‘acid clay’. This may be due to the presence of $H^{＋}$ in part as an exchangeable cation in the layer site of montmorillonite. All the works of this study ultimately suggest that an assesment of domestic bentonites in grade and quality should be accomplished through the quantitative XRD analysis and the ‘Total CEC’measurement.