• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.119-131
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• 2011

The asbestos contents in some representative building materials were analyzed using JIS (Japanese Industrial Standard) X-ray diffraction (XRD) method. The changes in mineral composition during analysis process and problems in JIS method were also examined. XRD analysis of some representative domestic building materials used for roof, wall, ceiling, and floor indicates that slate have the highest asbestos content having 6.87~6.93% of chrysotile. Other building materials analyzed in this study also have 1.35~3.98% of chrysotile contents. The XRD analysis results of asbestos contents in some domestic building materials are presented in this study. This method is very effective for the asbestos content evaluation of building materials according to newly modified asbestos content regulation (Law of Industrial Safety and Health, 2007-26) that limits asbestos content less than 0.1% by Ministry of Employment and Labor. Small amount of tremolite as well as chrysotile were also observed in some samples. With consideration of crystal shape, contents and geological occurrence, it is considered that tremolite is an associated mineral of chrysotile and is not intentionally added. Complemental analyses with optical microscope and SEM/EDS are also necessary because XRD method cannot distinguish asbestiform from non-asbestiform. The XRD method applied in this study is very effective in the asbestos content analysis of building materials, specially building materials showing high asbestos concentration in residues due to the high loss rate with ashing and acid dissolution procedure.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.233-257
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• 2023

Asbestos minerals are found at rocks and soils of the Hongseong and Bibong serpentine mines, western part of Chungnam. The area consists of and metasediment, and Mesozoic igneous intrusives with minor age-known gneiss complexes and Mesozoic sediments. With detailed geological investigations, rock samples for the serpentinite and amphibolite areas are collected at sites containing asbestos. Representative asbestos and rock samples are analysed by PLM, XRD, SEM and EPMA. Serpentinites are found as steeply dipping faults with adjacent gneiss complex to the NNE direction. Repeated alteration, including serpenitization and talcification, is found at the emplacement direction for the serpentinite body. Amphibollites occur as intrusives and stratiforms within the Precambrian gneiss complex. Serpentinite and amphibolite (or amphibole schist) contain amphiboles either as asbestiform or non-asbestiform. Varying amounts of asbestos minerals, including chrysotile, tremolite asbestos and actinolite asbestos, are found within the serpentinites. The asbestos minerals are found near the cracks or fractures and along the bedding plane. They occur as cross fiber, slip fiber and mass fiber types. Varying amounts of amphibole asbestos minerals, such as tremolite and actinolite asbestos, are found within amphibolites and as a mass fiber type. Overall results suggest that rocks of the serpentine mines contain serpentine and amphibole type asbestos minerals originated from the hydrothermal alteration. Considering construction nearby the mines and environmental risks by the asbestos, additional land management plans are required.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.6
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• pp.371-379
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• 2015

This study is purposed to seek the characteristics of both asbestos in accordance with acid and heat treatment for chrysotile and amosite used mainly as building materials. Results of acid treatment, the refractive index, the elongation sign, the extinction of acid-treated chrysotile were mostly similar to those of untreated chrysotile regardless of pH, elapsed time. But the characteristics of acid-treated chrysotile were different from those of untreated chrysotile after 8 weeks, at pH 1.2 acidic solution. When chrysotile treated with acid, weight ratio (%) of O and Mg fluctuated greatly in accordance with acid treatment unlike Si. But the change of constituents ratio (%) was small as time passed after acid treatment. The refractive index, the elongation sign and the extinction of acid-treated amosite were mostly similar to those of untreated amosite regardless of pH, elapsed time. When amosite was treated with acid, weight ratio (%) of Fe slightly increased. But in case of O, a contrary tendency was seen. Results of heat treatment, the higher the temperature, the more increased the refractive index of chrysotile. When chrysotile was heated for 10 minutes at $1,100^{\circ}C$, the elongation sign of chrysotile changed from positive(+) to negative(-). The extinction of chrysotile didn't change apparently in accordance with heat treatment. Also weight ratio (%) of O and Mg fluctuated greatly in accordance with heat treatment unlike Si. The higher the temperature, the more increased the refractive index of amosite. The elongation sign and the extinction of amosite didn't change apparently in accordance with heat treatment. Also weight ratio (%) of O and Fe fluctuated greatly in accordance with heat treatment. But weight ratio (%) of Si and Mg of heated amosite were mostly similar to those of untreated amosite regardless of temperature, heating time.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.77-88
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• 2016

Chrysotile is a 1:1 sheet silicate mineral belonging to serpentine group. It has been highlighted studies because of uses, shapes and structural characteristics of the fibrous chrysotile. However, it was designated as Class 1 carcinogen, so high attentions were being placed on detoxification studies of chrysotile. The objectives of this study were to investigate changes of mineralogical characteristics of chrysotile and to suggest detoxification mechanism of chrysotile by thermal decomposition. Samples for this study were obtained from LAB Chrysotile mine in Canada. The samples were heated in air in the range of 600 to $1,300^{\circ}C$. Changes of mineralogical characteristics such as crystal structure, shape, and chemical composition of the chrysotile fibers were examined by TG-DTA, XRD, FT-IR, TEM-EDS and SEM-EDS analyses. As a result of thermal decomposition, the fibrous chrysotile having hollow tube structure was dehydroxylated at $600-650^{\circ}C$ and transformed to disordered chrysotile by removal of OH at the octahedral sheet (MgOH) (Dehydroxylation 1). Upon increasing temperature, it was transformed to forsterite ($Mg_2SiO_4$) at $820^{\circ}C$ by rearrangement of Mg, Si and O (Dehydroxylation 2). In addition, crystal structure of forsterite had begun to transform at $800^{\circ}C$, and gradually grown 3-dimensionally to enstatite ($MgSiO_3$) by recrystallization after the heating above $1,100^{\circ}C$. And then finally transformed to spherical minerals. This study showed chrysotile structure was collapsed about $600-700^{\circ}C$ by dehydroxylation. And then the fibrous chrysotile was transformed to forsterite and enstatite, as non-hazardous minerals. Therefore, this study indicates heat treatment can be used to detoxification of chrysotile.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.87-99
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• 2013

The occurrence, mineralogical characteristics, and origin of the dolomite ores were investigated from major dolomite mines in South Korea. Mineralogical and textural properties of the ores and associated minerals were analyzed using X-ray diffraction, thin section petrography, and scanning electron microscopy. Dolomite ores were light to dark gray in color and mainly composed of dolomite in varying particle size with minor amounts of calcite, quartz and micas. Calcite, quartz, illite, feldspar, kaolin minerals, and chlorite occurred in local veins, dikes and alteration zones. Sepiolite and wollastonite occurred in the altered part of some mine. Asbestos minerals such as chrysotile and tremolite, however, were not identified in the present study. Reddish brown to yellow clay materials were mainly composed of illite, occasionally associated with kaolin minerals and smectite. These clay minerals might be a product of the local hydrothermal alteration related to the dyke intrusion and subsequent weathering. As well indicated in the previous studies, mineral composition, texture, and occurrence of the dolostone beds suggest their formation through the diagenesis of carbonate sediments deposited in the shallow sea during the Precambrian to Paleozoic period.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3177-3183
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• 2013

This paper deals with the robust design of the non-asbestos FCM(Fiber-elastomer Coated Metal) gasket. In order to this, the measurement of the shear stress based on the design of experimet using the orthogonal table was carried out and the control factors for shear stress using the larger-the-better SN ratios with the Taguchi method were evaluated. In addition, the analysis of variance for SN ratios was conducted. The temperature, pressure, duration time and humidity were selected as the control factors. The orthogonal table $L_9(3^4)$ was made of 3 levels for each factor and the measurement of shear stress was acomplished on the base of the table. Delta statistics of time is the highest value 0.93 and therefore the time affect the largest effect on the shear stress of gasket. Also from the analysis, the shear stress shows maximun at the duration time 80 sec, temperature $200^{\circ}C$, pressure 90 $kgf/cm^2$, humidity 60 %RH. P values of duration time and temperature as a results of the analysis of variance are 0.037 and 0.098. Therefore the analysis has significant each with 95% and 90% confidence level.

• Korean Journal of Heritage: History & Science
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• v.51 no.1
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• pp.4-31
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• 2018

The Neolithic pottery excavated from the Jungsandong site has been classified into four types of pottery (I: feldspar type, II: mica type, III: talc type and IV: asbestos type) according to their mineral composition. These four types of potteries generally appear to have undergone incomplete firing, while the level of oxidation in the type I pottery objects, which have a relatively higher clay content, was found to be particularly low. The type III objects, which have a high talc content, are judged to have been somewhat slow in removing carbon because they contain saponite belonging to the smectite group. Of the four types of pottery, type IV showed the highest redness and the most uniform characteristics, thus indicating a good level of oxidation. In particular, fixed carbide (C; 33.7 wt.%) with a thickness of about 1mm, and originating from organic substances, was detected inside the walls of the type I pottery, while the deep radial cracks in the outer surfaces of the pottery are thought to have been caused by repeated thermal shocks. Given that all of the pottery except for the type I artifacts are considered to be have been made for storage purposes, those containing talc and tremolite are easy to done liquid storing vessels based on an analysis of their material characteristics. As for the type II relics, which are composed of various minerals and exhibit poor physical properties, they seem to have been used for simple storage purposes. As domestic talc and asbestos mines were concentrated in the areas of Gyeonggi, Gangwon, Chungbuk, and Chungnam, it seems likely that talc and tremolite were produced as contiguous minerals. Considering the distance between the remains in Jungsandong and these mines and their geographical distribution, there is a possibility - albeit somewhat slight - that these mines were developed for the mining of various minerals. Although ultramafic rock masses - such as serpentine capable of generating talc and tremolite - have not been found in the Jungsandong area, limestone and biotite granite containing mica schist have been identified in the northwestern part of Yeongjong Island, indicating that small rock masses might have formed there in the past. Therefore, it is judged necessary to accumulate data on pottery containing talc and tremolite, other than the remains in Jungsandong, and to investigate the rocks and soils in the surrounding area with greater precision. The firing temperatures of the pottery found at the Jungsandong site were interpreted by analyzing the stability ranges of the mineral composition of each type. As a result, they have been estimated to range from 550 to $800^{\circ}C$ for the type I artifacts, and from 550 to $700^{\circ}C$ for the type I, II and IV artifacts. However, these temperatures are not the only factors to have affected their physical properties and firing temperature, and the types, particle sizes, and firing time of the clay should all be taken into consideration.