• Journal of the Mineralogical Society of Korea
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• v.29 no.2
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• pp.35-45
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• 2016

Clays, which are abundant in nature and eco-friendly, have been utilized throughout human history due to their characteristic physicochemical properties. Recently, a variety of clays such as montmorillonite, kaolinite, sepiolite and layered double hydroxide with or without chemical modification have been extensively studied for potential application in industries. Clays that possess a large specific surface area, high aspect ratio, nanometer sized layer thickness and controllable surface charge could be utilized as polymer fillers after appropriate chemical modifications. These modified clays can improve mechanical and gas barrier properties of polymer materials but also provide sustained antibacterial activity to polymer films. Furthermore, engineered clays can be utilized as scavengers for chemical or biological pollutants in water or soil, because they have desirable adsorption properties and chemical specificity. In this review, we are going to introduce recent researches on engineered clays for potential applications in future industries such as food packaging and environmental remediation.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.197-205
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• 2014

Study area (Jikjeon-ri) is located in south end of the Hadong anorthositic rocks. And along the south-western boundary, diorite intruded the Hadong anorthosite. Ilmenite ore bodies are extended in both anorthosite and diorite. And their occurrence in the diorite are not studied yet. While no particular textures are found in the ilmenite within the anorthosite, the ilmenite within the diorite shows characteristic exsolution texture, that is, ilmenite phases are separated into rutile and Fe-oxide and the ilmenite and Fe-oxide. MnO composition in ilmenite ratios are 2.14~3.74wt%, it has higher composition in diorite than that in anorthosite. The plagioclase composition display andesine ($An_{28.7-42.9}$) in the diorite and labradorite ($An_{57.1-72.8}$) in the anorthosite in composition. The exsolution of ilmenite has been developed during the cooling of partly melted ilmenite into rutile and Fe-oxides which is related to the intrusion of the diorite.

• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.383-392
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• 2006

Calcium carbonate stone deterioration has been intensified in urban area, mainly due to the action of atmospheric pollutant. Samples from the black surface layer were examined under petrographic and scanning electron microscope, coupled with energy dispersive X-ray analyser X-ray fluorescence and X-ray diffraction analysis was also carried out for chemical composition and mineral phase analysis, respectively. Moreover, sulphur isotope ratio was measured, in order to identify the origin of sulphate compounds in the black surface layer. Optical and electronic petrographic analysis indicated that gypsum and Quartz were contained in the black surface layer and led to microcracks. Microstructure and chemical composition analysis showed that the interface between black layer and original stone is not black but its characteristic is similar to black layer The results indicated that during deterioration process the black layer can be expanded gradually into the interface by adsorption of atmospheric pollutants. The sulphur isotope analysis demonstrates that there are different origins of the sulphur component in black surface layer.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.263-270
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• 2012

Two kinds of uranium species, oxidized uranium(VI) and reduced uranium(IV), were prepared to be interacted with goethite and montmorillonite to identify sorption characteristic of uranium species, which are very sensitive to the redox-reaction. The reduced uranium was prepared by diluting a substantial uranium(IV) that was concomitantly produced during a sulfate reduction via a sulfate-reducing bacterium. The sorption amount of uranium(IV) by the minerals was relatively lower than that of uranium(VI) because the aqueous uranium(IV) had fine colloidal forms to cause its weak adsorption onto the mineral surfaces. We found that the uranium(IV) phase has a nano-colloid character by the transmission electron microscope, suggesting that the uranium species possibly migrating with the flow of groundwater in underground environments can be the colloidal uranium(IV) as well as the ionic uranium(VI).

• Journal of the Mineralogical Society of Korea
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• v.19 no.3 s.49
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• pp.197-207
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• 2006

In the coal-bearing formations of the Janggi Group, which are reported as typical clastic sediments, several beds of volcaniclastic rocks are actually found in the Yeongil area. The coal-bearing formations generally exhibit alternating lithologic characteristics of pyroclastic and epiclastic sedimentary facies. Tuff and tuffaceous sandstone rich in pumice fragments are characteristic in the coal-bearing fermations. Diagenetic minerals found in the pyroclastic rocks of the upper and lower coal-bearing formations are montmorillonite, clinoptilolite, opal-CT, and quartz. Several tuffaceous beds correspond to the low-grade ores of zeolites and bentonite, and moreover, these ores mostly occur as thin beds less than 1 m in thickness. Thus, the potential of altered tuffaceous rocks as the resources typical of zeolite and bentonite seems to be low. However, based on mineral composition and CEC determinations, it can be evaluated that these tuffaceous rocks mostly have the promising potential for utilization as the absorbent-functional mineral resources such as acid clays, if these low-grade ores plus adjacent tuffaceous rocks are collectively exploited.

• Journal of the Mineralogical Society of Korea
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• v.4 no.2
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• pp.129-140
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• 1991

Two illite polytypes, 2M1 and 1Md, have been identified from the sericite deposits of the Bobae mine, Kimhae, Kyungsangnam-do. Each polytype has characteristic grain size, chemical composition, and occurrence. 2M1 illite occurs predominantly in the sericitic alteration zone, while 1Md illite occurs predominantly in the propylitic alteration zone, implying that the former was formed in the higher temperature than the latter. Illites can be subdivided into two types based on their crystal sizes;(1) the $\mu\textrm{m}$-sized illite which is below 0.01mm(100$\mu\textrm{m}$) in size and consists of 2M1 and 1Md type, (2) the mm-sized illite which is above 0.01mm in size and consists only of 2M1 type. Especially illite below 1$\mu\textrm{m}$ is premominantly of 1Md type. Therefore, it seems likely that illite crystal size is to some extent related to the polytype. XRD data show that there is no interstratified layer in illites regardless of the crystal size and polytype. Activity of muscovite component of the $\mu\textrm{m}$-sized illite is 0.843 while that of the mm-sized illite is 0.790. However, the latter is more similar to muscovite in crystal structure than the former is. The mm-sized illite has less Al and more Kthan the $\mu\textrm{m}$-sized illite. In both illites, Si contents show a positive relation to octahedral Mg. Fluid inclusion study and mineral association show that the formation temperature of illite is $270-330^{\circ}C$. The major chemical processes leading to the formation of sericitic deposit as well as the alteration zones are the leaching of SiO2 from the country rock and the addition of Al2O3 and K2O into the sericitic ores.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.209-224
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• 2008

Various types of high-purity limestone, which occurred in the Pungchon Formation, are examined to understand applied-mineralogical factors controlling their calcination characters with respect to the ore characters. To do this work, systematic characterization and determination were carried out for the limestone ores and their calcination products in a fixed heating condition, and the results were correlated and discussed. During the calcination experiment, a phase transition from calcite to quicklime begins to occur selectively in the physical weak zones such as grain boundary, cleavage and twin planes. All the fabrics of original limestones are preserved in the resultant quicklime. In addition, crystallinity of the quicklime was advanced, as the aging time of calcination was increased. Major controlling factors on the calcination effects of the high-purity limestone are elucidated to be the degree of development of cleavage and twin, together with crystallinity and textures in the limestone ore. Especially, lower crystallinity and dense interlocking fabrics obviously play advantageous role in all the calcination characters. But the development of cleavage and twin affects negatively on the calcination characters on account of favoring decrepitaion of quicklime in the lime manufacturing. Thus, the high-purity limestones characteristic of marble fabrics and relatively lower crystallinity are comparatively advantageous for the uses of lime manufacture.

• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.315-327
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• 2002

Al-pillared clay was synthesized by constructing pillars of aluminum oxides at the interlayer of montmorillonite in bentonite. XRD, DTA and chemical analyses of Al-pillared clay were performed to examine mineralogical properties. Batch adsorption experiments were also conducted to determine the adsorption properties of this synthesized clay for phosphate ions. XRD analyses showed that the interlayer space of Al-pillared clay expanded to 18.03 $\AA$ at room temperature and shifted to $17 \AA$ after heating to $550^{\circ}C$. A small change in interlayer space after heating indicates high thermal stability. The interlayer expansion by glycerol was also very small. From DTA analyses, pillared clay showed the characteristic endothermic peaks at 270 and $420^{\circ}C$ , which might be caused by dehydration in framework of pillars between interlayers. Adsorption experiment revealed that Al-pillared clay had an excellent adsorption capacity to the phosphate ions, whereas montmorillonite had very low adsorption capacity to phosphate ions. In phosphate solution concentration up to 300 mg/L, 2 g of pillared clay could uptake almost 100% of phosphate ions from 20 mL of solution. After heat treatment of the phosphate adsorbed pillared clay at 50$0^{\circ}C$ to remove phosphate, the calcined pillared clay could adsorb phosphate ions with a little decreased adsorption efficiency. This fact indicates that Al-pillared clay can be recycled for the adsorption of phosphate ions.

• Journal of the Mineralogical Society of Korea
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• v.17 no.2
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• pp.135-145
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• 2004

A zeolitic bentonite, which exhibits whitish appearance and contains considerable amounts (nearly 〉 5%) of zeolites, frequently occurs as thin beds less than 1 m in Yeongil area. The bentonites are mostly found in closely association with zeolite beds in the Nuldaeri Tuff and Coal-bearing formations of the Janggi Croup. A discordant occurrence of the bentonite against the bedding plane is also locally found. Montmorillonite, the major mineral constituent of the bentonite, is mostly associated with clinoptilolite as a zeolite. However, instead of clinoptilolite, mordenite is sometimes included in the case of more silicic bentonite, and heulandite in the less silicic one. It is characteristic that the mordenite is accompanied by lots of opal-CT in the silicic bentonite. SEM observations characteristically indicate that these authigenic phases, especially the montmorillonite and zeolite, nearly coexist as mixtures not forming a fine-scale zoning. The zeolitic bentonite seems to be formed in the comparatively silicic pore fluid at the alkaline condition accompanying pH fluctuation Compared to the zeolite-free normal bentonite, the zeolitic types exhibit somewhat higher REE abundance. These chemical characteristics, together with modes of occurrences and authigenic mineral associations, may suggest that the zeolitic bentonite is not merely diagenetic products and a possible hydrothermal alteration could not be excluded in the bentonite genesis.