• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.253-263
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• 2011

Mineralogical characteristics of garnierite ores from the Nakety, Kouaoua, and Ouaco Ni laterite deposits in New Caledonia are investigated using optical microscopy, powder X-ray diffractometer, and electron proble microanalyzer. Green garnierite ores have colloform, cellular, and boxwork texture, which are formed by precipitation under low temperature surface environment. They are mainly composed of Ni-bearing talc~willemseite series mineral and partly of lizardite. In Ni-bearing talc~willemseite series mineral, NiO contents are Ouaco (average 40.63%), Nakety (average 28.58%), and Kouaoua (average 24.90%), in descending order. Ni atomic percentage replacing Mg in octahedral site are 43.5~85.0%. Dark brown garnierite ores show cellular or boxwork texture, and consist of lizardite~Ni lizardite with some Ni-bearing talc~willemseite series mineral. Ni contents in lizardite~Ni lizardite are 1.14~4.06 wt. % and Ni atomic percentage replacing Mg in octahedral site 1.7~6.8%. Low NiO content in dark brown garnierite attributes to high Fe content replacing Mg in octahedral site.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.126-138
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• 1997

Serpentinite of the Yesan-Gongju-Cheongyang area has been formed by serpentinization of ultramafic rocks. The ultramafic rock might be composed mainly of oilvine with minor pyroxene and amphibole. Olivine has a considerably restricted chemical compositional ranging from Fo90 to Fo93. Fresh serpentinite containing large amount of oilvine is usually massive in occurrence and dark green to black in color. Serpentine minerals occur not only as major mineral of serpentinite, but also as remnants in the talc ore which was formed from serpentinite. XRD study indicates that antigorie is the most abundant serpentine mineral of the serpentinite. Serpentinite consisting of antigorite usually shows non-pseudomorphic texture, whereas that consisting of lizardite shows pseudomorphic texture. Antigorite is found along the margins or fractures of olivine grains resulting in the formation of network of magnetite which was formed at the time of serpentinization. Lizardite, subordinate constituent mineral of serpentinite, frequently shows pseudomorphic mesh-texture after olivine. The chemical differences between antigorite and lizardite/chrysotile are small, so both minerals are not easily discernible with the electron microprobe. Antigorite occuers as elongate blades, flakes, or plates forming interpenetrating texture to obliterate previous textures. SEM study also shows that most serpentine minerals occur in platy or tabular form rather than in asbestiform. Fractures formed after main serpentinization are observed within the pseudomorphic central olivine grain. Careful observation of the serpentine pseudomorphs gives a great deal of data on the pre-serpentinization nature of the serpentine pseudomorphs gives a great deal of data on the pre-serpentinization nature of the ultramafic rocks. It is inferred that the serpentinization took place after the emplacement of ultramafic body into the relatively wet environment ceased and the cooling intrusive body crossed into the stability field of serpentine. It is inferred that the final pervasive serpentinization took place over a long time, by hydrothermal water supplied through the fracture system produced during emplacement of ultramafic rock.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.227-234
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• 2010

We investigated the effect of dry grinding of laterite on the extraction of nickel and cobalt. The major chemical compositions of the sample for this work were $SiO_2$, $Fe_2O_3$ and MgO. The sample contained 0.81% Ni and 0.02% Co. The major minerals of the sample were lizardite and quartz with minor amounts of forsterite and enstatite. The mean particle size, specific surface area and density of the ground sample decreased with increasing grinding time, while the amorphization of lizardite increased as identified by XRD analysis. The grinding enabled the extraction ratio of Ni and Co to increase by the breakdown of Mg-OH bonding in the lizardite structure. However, physical properties of quartz were not changed by grinding. The extraction ratio of Ni and Co increased with increasing grinding time. Approximately 80% of Ni and Co were extracted regardless of the kind of acid solutions when the sample was ground for 60 minutes.

• Journal of the Mineralogical Society of Korea
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• v.30 no.4
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• pp.161-172
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• 2017

Clay minerals play a major role in the geochemical cycles of metals in the Critical Zone, the Earth surface-layer ranging from the groundwater bottom to the tree tops. Atomistic scale research of the very fine particles can help understand the fundamental mechanisms of the important geochemical processes and possibly apply to development of hybrid nanomaterials. Molecular dynamics (MD) simulations can provide atomistic level insights into the crystal structures of clay minerals and the chemical reactivity. Classical MD simulations use a force field which is a parameter set of interatomic pair potentials. The ClayFF force field has been widely used in the MD simulations of dioctahedral clay minerals as the force field was developed mainly based on dioctahedral phyllosilicates. The ClayFF is often used also for trioctahedral mineral simulations, but disagreement exits in selection of the interatomic potential parameters, particularly for Mg atom-types of the octahedral sheet. In this study, MD simulations were performed for trioctahedral clay minerals such as brucite, lizardite, and talc, to test how the two different Mg atom types (i.e., 'mgo' or 'mgh') affect the simulation results. The structural parameters such as lattice parameters and interatomic distances were relatively insensitive to the choice of the parameter, but the vibrational power spectra of hydroxyls were more sensitive to the choice of the parameter particularly for lizardite.

• Economic and Environmental Geology
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• v.26 no.1
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• pp.1-10
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• 1993

The Andong serpentinite body is distributed along the Andong fault, and shows an elliptical shape. The serpentinite is composed of serpentine minerals and other various minerals such as forsterite, pyroxene, talc, tremolite, chlorite, prehnite, calcite and dolomite. The serpentine minerals consist primarily of lizardite with minor chrysotile. Antigorite rarely occurs in some veins. The serpentinite is largely divided into two alteration zones by the occurrence and mineral assemblages. One of the alteration zones is composed of a large amount of serpentine minerals. The other is characterized by tremolite and chlorite. The alteration zone composed of tremolite and chlorite seems to have been formed by hydrothermal alteration after the formation of serpentinite. It is considered that the serpentinite have been formed by alteration of the ultramafic rock such as peridotite.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.1
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• pp.39-50
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• 2009

This study is for the occurrence types of asbestos within 2 serpentinite mines, Baekdong and Kwangsi, Chungnam. They were exploited as serpentinite mines for several decades and closed in the 1980's. Asbestos with associated minerals were collected from the serpentinite bodies. They were examined with microscopes and FESEM, and analysed with EPMA, XRD and EDX to confirm for the types and/or compositions of the minerals. The serpentinites contain asbestos and nonasbestos minerals. Asbestos include chrysotile, tremolite and actinolite. The chrysotiles occur as veins of several mm to cm thickness with random directions. The tremolite and actinolite occur along cracks and fractures of several cm to ten cm thickness. They show mineralogical characteristics showing common asbestos under the microscope. Non-asbestos including chrysotile, lizardite, antigorite, tremolite and actinolite were also found within the serpentinite. The serpentines form pseudomorphic mesh textures, and also show hourglass or ribbon textures. The tremolite and actinolite were formed from the alterations of the pyroxenes and amphiboles, and plot between tremolite and magnesio hornblende. Tremolitic grains are colorless and occur as commonly elongated grains whereas the magnesio hornblende grains mainly show light green and occur as subhedral to euhedral grains. Overall results suggest that three types of asbestos are found in the Baekdong and Kwangsi serpentinite mines with varieties of the occurrences. Based on the occurrence types for the asbestos, additional studies are required for the asbestos of the top soil and the air.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.1
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• pp.35-40
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• 2013

Objectives: Asbestos contents of crushed serpentine rocks and airborne fiber concentrations of workers were determined at two serpentine quarries and a steel mill. Methods: Bulk samples of uncrushed and crushed serpentine rocks were collected and analyzed by PLM and TEM. Airborne asbestos samples were collected from the breathing zone of workers and the vicinity of working area and analyzed by PCM and TEM. Results: Chrysotile was identified with antigorite, lizardite and non-asbestiform actinolite in bulk samples. The arithmetic means of chrysotile contents in crushed serpentines were 0.11, 0.01, 0.42%(W/W) by quarry A, quarry B and a steel mill, respectively. The asbestos concentrations of all personal samples were less than 0.1 f/cc which is the permissible exposure limit of workers in Korea. The arithmetic means of airborne asbestos concentrations were 0.017 f/cc and 0.009 f/cc in personal samples collected from two serpentine quarries. The asbestos concentrations of all personal samples collected from a steel mill were less than LODs by PCM analysis but asbestos was detected in area samples by TEM. By the job tasks of serpentine quarries, crusher/separator operation generated the highest exposure to airborne asbestos. Conclusions: Although chrysotile contents in crushed serpentines of quarries were less the permissible level, the highest exposure of workers in serpentine quarries reached up to 76% of the permissible level of airborne asbestos. There were also possibilities of occupational exposure to airborne asbestos in a steel mill. The present exposure study should encourage further survey and occupational control of quarries producing serpentine or other types of asbestos-bearing rocks.

• Journal of the Mineralogical Society of Korea
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• v.25 no.1
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• pp.9-21
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• 2012

Six serpentine mines are found in South Korea. We investigated occurrence, characteristics and origin of constituent minerals of Bibong serpentine mine in Chungcheongnam-do. We also analyzed the properties of serpentine minerals using XRD, XRF, SEM/EDS, FT-IR, EPMA and polarized microscope. The serpentinite of Bibong mine occurs as intruded body within the Precambrian metasedimentary rocks. Various minerals such as serpentine, forsterite, pyroxene, tremolite, magnetite, chlorite, mica, talc and dolomite are occurre. Five distinctive mineral assemblage types are observed in the serpentinite: (A) serpentine-forsterite, (B) serpentine, (C) serpentine-chlorite (vermiculite), (D) serpentine-tremolite, (E) tremolite-chlorite. Lizardite and antigorite are mainly occurred as serpentine minerals and chrysotile is partly included. From the study of mineral compositions and occurrence of serpentinite body, serpentine formed by hydrothermal alteration of ultramafic rock consisting mainly of forsterite, and altered minerals such as chlorite and tremolite subsequently formed by secondary hydrothermal alteration.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.1-11
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• 2016

Chrysotile is well known as a fibrous mineral in serpentinite by the previous studies in S. Korea. Previous studies in other countries showed that antigorite also occurred as asbestiform and harmful to humans. Therefore, the objective of this study was to investigate types and characteristics of fibrous serpentine minerals occurred in serpentinite in Hongseong, Chungnam and Gapyeong, Gyeonggi in S. Korea. XRD, SEM-EDS, PLM and EPMA mapping analyses were used to examine the occurrence and formation mechanism of serpentine minerals. Serpentinization partially occurred in amphibole-schist and calc-schist at two study sites, Hongseong, Chungnam and Gapyeong, Gyeonggi, respectively. Both chrysotile and antigorite occurred as a fibrous mineral at Hongseong site, but chrysotile occurred as a fibrous mineral at Gapyeong site. Based on PLM analysis with dispersion staining, the chrysotile was observed horizontally magenta and vertically blue colors. The antigorite appeared as horizontally gold to golden magenta and vertically blue magenta colors under central stop dispersion staining objective(DSO). PLM and SEM analyses showed the fibrous minerals were formed from plate form of serpentine minerals or by hydrothermal alternation of primary minerals. The EPMA mapping showed that Mg contents in chrysotile is relatively higher than that in antigorite while Si and O contents in antigorite is higher than them in chrysotile. However, more studies are necessary to know the exact variation in chemical composition of chrysotile and antigorite. These results indicate that even though asbestiform antigorite found associated with asbestos chrysotile in serpentinites, the fibrous antigorite can be distinguished from chrysotile by different dispersion staining colors.