• The Journal of the Petrological Society of Korea
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• v.24 no.1
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• pp.11-24
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• 2015

In this study, the stone used for three storied pagoda of Bulguksa Temple, which is easy to access due to works for dismantle and restore will be analyzed on the basis of petrographic study, magnetic susceptibility, and ${\gamma}$-ray spectrometer, and identify petrographic characteristics. Also we will select candidate areas of fresh rock to change the stone used for three storied stone pagoda as from its provenance is presumed. According to the results of visual inspection, the stones used for the three storied stone pagoda are similar to the features of Namsan granite, which is distributed around Gyeongju-si, and when it comes to the section of the stupa finial, the features of all the parts from the stupa finial is similar to Namsan granite except for the section of Jeweled cover. On the other hand, the color, the composition, and the mineral size of the stones in the section from the part of jeweled cover are similar to Tohamsan granite. As a result of none-destruction inspection, it seems that the stones used for the three stories stone pagoda except for the section of jeweled cover are similar to the values for the magnetic susceptibility and the ${\gamma}$-ray spectrometer. On the other hand, Jeweled cover and the values of Tohamsan granite are alike. Namsan granite is appropriate in case that the stone used for three storied stone pagoda must be replaced to fresh rock because of damage by weathering. Meanwhile, Namsan granite is seperated from Yangsan fault. Due to this fact, Namsan granite appears to not only Mt. Namsan in Gyeongju, but also Dongcheon-dong, Gyeongju, and Huenggok-ri, Pohang. As a result, these two areas are suitable to the candidate area to change the stone used for three storied stone pagoda.

• Journal of the Mineralogical Society of Korea
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• v.22 no.1
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• pp.35-47
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• 2009

The deteriorations of stone monuments located in Gyeongju area are predicted in a modeling study. Artificial rain and accelerated weathering test are here applied to the Gyeongju Namsan granite and cement mortar. They are reacted with pH 4.0, pH 8.0 and pH 5.6 rain, respectively. The two former values are the limited acidity values in the Gyeongju (the acidity of rain of the Gyeongju were pH $4.93{\sim}6.39$ in 2005) and the latter is the limited acidity of acid rain. The rains of pH 5.6 and pH 8.0 reach close to a value of pH 7.0 after the reaction with the Gyeongju Namsan granite. After application of the artificial rain and weathering test, the weight of specimens were reduced and the contents of soluble ions in the specimens were increased. These results are attributable to solution of minerals in the specimens. At first, the microlithic have dissolved in ground from the reaction with acid rain. And then mainly quartz, plagioclase and orthoclase bound by the microlithic are disintegrated. The cement mortars are dissolved after the reaction with not only acid but alkali rain. The concentrations of ions in the dissolved cement mortar are higher than those in granite.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.567-578
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• 2018

A nondestructive petrological investigation was carried out to identify the original location and form of the Gyeongju Seated Stone Buddha with Square Pedestals in the Blue House (so-called Stone Buddha in the Blue House). The Statue is a representative stone Buddha statue of Silla (9th century) but its original location is controversial and some parts were missing. Based on the petrological observation, magnetic susceptibility and gamma spectrometry, its stone material was identified as medium-grained alkali feldspar granite. This kind of granites are widely found in the Namsan, Gyeongju. It is very likely that the Namsan granites are the source of rock of the Stone Buddha. The Yudeoksa (Igeosaji temple site) and Namsan are possible to be the original home of the Buddha Statue since there are petrologically identical alkali feldspar granite outcrop distributed in Namsan and stone heritage made of the same stone type in both places. An investigation on the square middle stone base in the Chuncheon National Museum reveals that it is less likely to be the missing part of the Buddha statue as the stone base is fine- to medium-grained pink feldspar granite and has different magnetic susceptibility from the Buddha statue. This study confirmed the contribution and significance of petrological investigation to identification of stone heritage in Korea.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.63-71
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• 2010

The artificial rains having different pH and weathering simulation test were performed for Gyeongju Namsan granite and dacitic tuff to predict the role of acid rain in the deterioration of stone monuments located in Gyeongju area. The pH 4.0 rain reacted with the fresh granite showed near neutral pH at the early stage due to the hydrolysis of minerals in the rock surface. But the pH changed back to the initial pH in the later stage. On the other hand, the pH 5.6 rain showed the neutral pH for a longer time than the experiment with pH 4.0 rain, reflecting slower reaction of minerals due to the weaker acidity. When the pH 5.6 rain reacted with the weathered granite, the water showed neutral pH longer than the case of the fresh granite. The similar tendencies were observed in the experiment of dacitic tuff, except that the pH 4.0 rain reacted with dacitic tuff took a longer time to go back to the initial pH as compared with the case of granite. These results may due to the differences in mineral composition and texture of two rocks. Dacitic tuff contains more fine-grained or glassy groundmass than granite and is more reactive with weaker acid rain. It was predicted that the weight loss and strength decrease rate of dacitic tuff would be approximatetly twice relative to those of granite in the same experimental environment.

• Journal of the Korean association of regional geographers
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• v.11 no.4
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• pp.440-452
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• 2005

The granites in the Gyeongju area are represented by the Namsan granites and the Tohamsan granodiorites. In this study I examined the geomorphological and geological characteristics of the granite landforms in the Gyeongju area. Joint, tor and corestones are most identifiable geomorphological and geological structure in the study areas. Tor in the Namsan granites is well developed and mainly composed of cubic corestones. Petrographical features of the stones used for the stone-built cultural properties are compared with those of the granites cropped out nearby. Additionally radiogenic element contents (K, Th, U) were acquired for comparison by gamma-ray spectrometer analysis. Most stones from the stone-built cultural properties in the Bulguksa Temple are very similar to the Namsan granites in terms of petrography, radiogenic elements. On the contrary almost all stones from the Seokguram Grotto share common petrographical, physical and chemical characteristics with the Tohamsan granodiorites. Therefore it can be suggested that the stones in the Bulguksa Temple were supplied from Namsan, and that the stones in the Seokgurarn Grotto were collected at nearby Tohamsan.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.79-88
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• 2016

A derelict bridge called WoljungGyo is being restored in Gyeongju, the capital city of ancient Silla. WoljungGyo was originally built in 760AD, and later rebuilt in 1280AD during the Goryeo Kingdom. The bridge lasted in working condition for at least 520 years. The bridge was uncovered to the remains of both abutments and four piers, with only one or two steps remaining. The provenance of the WoljungGyo stone relics was investigated to decide the type of stone for the restoration works. Field survey were carried out in the whole area of Gyeongju-Si with petrological investigation for the stone relics. Results of the study present that Namsan granite was used in those days for building of the WoljungGyo. It is seems that the used stones were obtained from tor or core stone around the Tongil-jeon and Tap-gok area in the east side of Mt. Namsan.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.183-192
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• 2008

Stone cultural heritages in Korea are mostly situated out door without any notable protection thus there are severe damage from chemical and biological weathering. This in turn, causes deformation and structural damage. To counter act this problem and to increase durability, various kinds of conservation materials are used in the conservation and restoration treatment. However, there are not many practical and technological experiment done on this subject. This paper attempts quantitative evaluation of effectiveness of ethylsilicate based resin for Namsan granite in Gyeongju. When two different materials with different ethylsilicate concentration were compared, the result indicated decrease of absorption and porosity with increase of ultrasonic velocities, uniaxial compressive strength, elastic constant, tensile strength and Poisson's ratio. In addition, comparison of physical characteristic of the conservation material resulted favorably toward ones with higher concentration of ethylsilicate. This is due to the ethylsilicates characteristic to fill the internal pores of stone. There is discolouration of stone surface after treatment with conservation material. This was more prominent with the product of higher ethylsilicate concentration.

• 보존과학연구
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• s.28
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• pp.39-58
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• 2007

The Seated Buddha image carved on rock surface of Yuneulgok in Bae-ri, Gyeongju constituted of alkali feldspar granite. There is surface weathering by abrasion, exfoliation and break out. As a result various experiment was carried out testing rock material property to quantitatively grade weathering. Besides, this study is focused on properties of rock and correlation between things. Additionally, comparison of chemical properties to nondestructive weathering grade in the buddha image carved on rock. This result utilized on important resource for scientific conservation system compared with weathering appearance.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.135-145
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• 2015

In order to predict the deterioration of stone monument due to acid fog, an artificial fog test using pH4.0 and pH5.6 was applied to the Gyeongju Namsan granite, decite and marble. After the test had weathered Gyeongju Namsan granite a larger weight reduction due to acid fog than fresh one. Decite has shown the most significant changes among the tested rocks with about 0.005 % of weight reduction. Decite and weathered granite will have considerable weight reduction due to acid rain than the acid fog, whereas the marble was expected to show a weight reduction regardless of the phase of water. The porosity and water absorption rate of weathered granite had significantly increased. This result means that the weathered rock is predicted to be more susceptible to acid fog than the fresh rock. The absorption rate of the marble after the test had shown approximately 50 % increase. The color of the samples had slightly changed towards yellow, such tendency was greater shown in weathered rocks. The marble reacted with acid fog had an increased whiteness. A large amount of cation in the samples is caused mainly by the dissociation of minerals through the reaction with acid fog.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.405-413
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• 2012

This study demonstrates the consolidation effect of ethylsilicate consolidants considering material characteristics and weathering degree of Samneunggyeseongakyukjonbul(rock-carved Yukjonbul Buddha in Samneung Valley) in Namsan, Gyeongju. The buddha statue is composed of alkali feldspar granite and contains numerous sets of joint with exfoliation and granular disintegration, therefore the statue is necessary to be treated for surface strength. The laboratory and in-situ tests of consolidation effect showed more increase of ultrasonic velocity that KSE 300, a relatively highly concentrated consolidant, performed more increase of ultrasonic velocity and decrease of porosity than others after treatments in weathered granite. And the consolidated rock with OH 100 was more resistant to salt weathering. For the buddha statues, KSE 300 is more applicable to enhance surface strength because it showed higher consolidation effect for long term than OH 100 and the statues has not been weathered by salts.