Presentation Information
[O12-P50]Identification of the Mineral Phase Analysis of Izu-Wakakusa Stone Using XRD and an Investigation of Hydrothermal Alteration
*Yusuke Kitamura1, *Yuso Sugiyama1, Taiga Tsuyuki1, Rei Uchisasai1, Haruta Endo1, Yuka Tanaka1, Shiho Mimuro1 (1. Nirayama high school)
Keywords:
powder X-ray diffraction,green tuff,hydrothermal alteration
1. Background and Objectives
Izu Peninsula has produced its high-quality stone, “Izu Stone”, which was used for the stone walls of Edo Castle and Bank of Japan Head Office [1]. We focused on a particular type of stone, known as “Izu-Wakakusa Stone”. This greenish-blue tuff undergone hydrothermal alteration 20 million years ago [2]. Despite its historical and cultural significance, current quarrying operations are minimal, and many existing structures featuring Izu Stone are increasingly being demolished. To address this situation and enhance public recognition of this material, the objective of this study is to clarify the mineral composition of Izu-Wakakusa Stone and examine the hydrothermal processes involved in its formation. In this paper, "Izu-Wakakusa Stone" specifically refers to green Izu Stone tuff that has undergone such alteration.
2. Data and Methods
In this study, powder X-ray diffraction (XRD) was employed to elucidate the mineralogical composition of Izu-Wakakusa Stone. XRD allows for the identification and quantification of constituent substances by comparing the measured diffraction patterns with the spectra of known substances [3]. The XRD measurements were conducted at the Hamamatsu Technical Support Center using Rigaku RINT-2500X. The measurement conditions were set to a tube voltage of 40 kV and a tube current of 40 mA, with a scanning speed of 4.000°/min and a step width of 0.020°. Since standard samples could not be prepared for this study, Rietveld analysis—a method capable of accurately determining weight fractions even in complex mixtures—was utilized for quantitative assessment. Match! 4 was used as the spectral analysis tool.
Three samples were used in this study: two collected from eastern Izunokuni City, Shizuoka Prefecture (designated as Wakakusa Stone 1 and Wakakusa Stone 2), and one collected from western Izunokuni City, (designated as Wakakusa Stone 3). Wakakusa Stone 2 represents the variety commonly referred to as "Wakakusa Stone" and Wakakusa Stone 3 is known as "Tosawa Stone".
3. Results
Comparative analysis with the database identified quartz, albite, and chlorite in all samples. Additionally, illite was detected in Wakakusa Stone 2 and 3, while augite was identified in Wakakusa Stone 1. Based on these findings, Rietveld analysis was performed, yielding the following compositions:
Wakakusa Stone 1: Quartz (13.7%), Albite (42.1%), Augite (21.7%), and Chlorite (22.5%)
Wakakusa Stone 2: Quartz (29.9%), Albite (32.7%), Illite (15.3%), and Chlorite (22.1%)
Wakakusa Stone 3: Quartz (28.1%), Albite (20.1%), Illite (4.8%), and Chlorite (47.1%)
Smectites were not detected in any of the samples. As the types of constituent minerals and their approximate compositions have been successfully identified, we consider these data to be sufficient for the subsequent evaluation of hydrothermal processes, which is the primary objective of this study.
4. Discussion and Future Outlook
In hydrothermal processes, it is well established that pH, pressure, and the water/rock ratio play significant roles [4]; however, this study focuses on temperature, the most influential factor. It is known that during hydrothermal alteration, smectite transforms into chlorite as the temperature increases [4]. Based on the presence of illite and chlorite, and the complete absence of smectite—referencing the temperature ranges established in [4]—it is inferred that Wakakusa Stone underwent hydrothermal alteration at temperatures between approximately 200℃ and 300℃.
Future research will focus on improving analytical precision through elemental analysis and XRD using standard samples. Concurrently, we will proceed toward the goal of this research: the synthetic replication of Wakakusa Stone. We hypothesize that by using metal capsules to simulate a high-pressure environment at approximately 300°C, it may be possible to reproduce the formation conditions of the stone.
5. Acknowledgements
We express our sincere gratitude to Mr. Hideaki Kawaguchi of Marui Jutaku and Senior Researcher Daisuke Endo of the Beautiful Izu Creation Center for their invaluable cooperation in this study. We also extend our thanks to the Hamamatsu Technical Support Center for their technical assistance. This work was supported by a research grant from Yamazaki Natural Science Foundation in 2025.
6. References
[1] Izu Stone Culture Research Association
[2] Tobu Create Takeda. What is Izu Stone?
[3] Japan Analytical Instruments Manufacturers' Association. Principles and applications of X-ray diffractometers
[4] Yoshimura, T. (2003). Diagenesis and clay minerals. Clay Science (Nendo Kagaku), 42(3), 167-173.
Izu Peninsula has produced its high-quality stone, “Izu Stone”, which was used for the stone walls of Edo Castle and Bank of Japan Head Office [1]. We focused on a particular type of stone, known as “Izu-Wakakusa Stone”. This greenish-blue tuff undergone hydrothermal alteration 20 million years ago [2]. Despite its historical and cultural significance, current quarrying operations are minimal, and many existing structures featuring Izu Stone are increasingly being demolished. To address this situation and enhance public recognition of this material, the objective of this study is to clarify the mineral composition of Izu-Wakakusa Stone and examine the hydrothermal processes involved in its formation. In this paper, "Izu-Wakakusa Stone" specifically refers to green Izu Stone tuff that has undergone such alteration.
2. Data and Methods
In this study, powder X-ray diffraction (XRD) was employed to elucidate the mineralogical composition of Izu-Wakakusa Stone. XRD allows for the identification and quantification of constituent substances by comparing the measured diffraction patterns with the spectra of known substances [3]. The XRD measurements were conducted at the Hamamatsu Technical Support Center using Rigaku RINT-2500X. The measurement conditions were set to a tube voltage of 40 kV and a tube current of 40 mA, with a scanning speed of 4.000°/min and a step width of 0.020°. Since standard samples could not be prepared for this study, Rietveld analysis—a method capable of accurately determining weight fractions even in complex mixtures—was utilized for quantitative assessment. Match! 4 was used as the spectral analysis tool.
Three samples were used in this study: two collected from eastern Izunokuni City, Shizuoka Prefecture (designated as Wakakusa Stone 1 and Wakakusa Stone 2), and one collected from western Izunokuni City, (designated as Wakakusa Stone 3). Wakakusa Stone 2 represents the variety commonly referred to as "Wakakusa Stone" and Wakakusa Stone 3 is known as "Tosawa Stone".
3. Results
Comparative analysis with the database identified quartz, albite, and chlorite in all samples. Additionally, illite was detected in Wakakusa Stone 2 and 3, while augite was identified in Wakakusa Stone 1. Based on these findings, Rietveld analysis was performed, yielding the following compositions:
Wakakusa Stone 1: Quartz (13.7%), Albite (42.1%), Augite (21.7%), and Chlorite (22.5%)
Wakakusa Stone 2: Quartz (29.9%), Albite (32.7%), Illite (15.3%), and Chlorite (22.1%)
Wakakusa Stone 3: Quartz (28.1%), Albite (20.1%), Illite (4.8%), and Chlorite (47.1%)
Smectites were not detected in any of the samples. As the types of constituent minerals and their approximate compositions have been successfully identified, we consider these data to be sufficient for the subsequent evaluation of hydrothermal processes, which is the primary objective of this study.
4. Discussion and Future Outlook
In hydrothermal processes, it is well established that pH, pressure, and the water/rock ratio play significant roles [4]; however, this study focuses on temperature, the most influential factor. It is known that during hydrothermal alteration, smectite transforms into chlorite as the temperature increases [4]. Based on the presence of illite and chlorite, and the complete absence of smectite—referencing the temperature ranges established in [4]—it is inferred that Wakakusa Stone underwent hydrothermal alteration at temperatures between approximately 200℃ and 300℃.
Future research will focus on improving analytical precision through elemental analysis and XRD using standard samples. Concurrently, we will proceed toward the goal of this research: the synthetic replication of Wakakusa Stone. We hypothesize that by using metal capsules to simulate a high-pressure environment at approximately 300°C, it may be possible to reproduce the formation conditions of the stone.
5. Acknowledgements
We express our sincere gratitude to Mr. Hideaki Kawaguchi of Marui Jutaku and Senior Researcher Daisuke Endo of the Beautiful Izu Creation Center for their invaluable cooperation in this study. We also extend our thanks to the Hamamatsu Technical Support Center for their technical assistance. This work was supported by a research grant from Yamazaki Natural Science Foundation in 2025.
6. References
[1] Izu Stone Culture Research Association
[2] Tobu Create Takeda. What is Izu Stone?
[3] Japan Analytical Instruments Manufacturers' Association. Principles and applications of X-ray diffractometers
[4] Yoshimura, T. (2003). Diagenesis and clay minerals. Clay Science (Nendo Kagaku), 42(3), 167-173.