1:45 PM - 3:15 PM
[O11-P47] Is hematite the cause of the red color of Makado stone? 2
Keywords:Makado stone, Aso-4, component analysis, Fe2O3
Motivation, Purpose, and Hypothesis of the Study
Makadoishi (Makado stone) produced in Umamon, Amizu-cho, Kumauzu City has a characteristic red color, but the reason for this color is unknown, so we decided to investigate the cause of the red color. From past literature[1] , we hypothesized that the cause of the red color was Fe2O3 (hematite), and began our research.
Research Contents
(1) Literature survey and experiments
(1) Literature survey and experiments (2) Density and magnetism are not significantly different, and the only differences are color and hardness.
(1) Literature survey and experiments
The red iron oxides are Fe2O3 and FeO(OH) [2][3][4].
When we conducted an experiment using iron nails, we found that Fe2O2 did not change even when heated with a gas burner, whereas FeO(OH) did.
In contrast, FeO(OH) formed orange rust in about half a day after being soaked in water, indicating that Fe2O3 requires higher temperatures to be formed.
OH, which is a kind of Fe2O3, was found to require higher temperatures for its formation.
Aso-4, magnetite, and hornblende were soaked in water and exposed to air for observation. Aso-4, magnetite, and hornblende were immersed in water and exposed to air.
Aso-4, magnetite, and hornblende were soaked in water and exposed to air, and no change was observed after several months.
(2) Component analysis and firing test
(1) X-ray fluorescence analysis and X-ray diffraction were conducted.
X-ray fluorescence analysis and X-ray diffraction were conducted.
(2) Compositional analysis and firing test (i) X-ray fluorescence analysis and X-ray diffraction were conducted.
(3) X-ray diffraction: The presence of Fe2O3 could not be clearly confirmed in any of the samples.
(2) Makado stone and Aso-4 were heated sufficiently at different temperatures (300°C and 1,000°C) for 24 hours using an electric furnace.
Firing experiment: Both samples heated at 1,000°C turned red.
It was considered that the iron in the rock changed to Fe2O3[5][6] and that the factor responsible for the color of the makado stone was the iron in the rock.
(3) Field survey
We considered the cause of the red color from the distribution[7][8].
We were able to confirm the boundary between the Bamon Stone and Aso-4 at several locations. The boundaries were scattered, with slopes varying from place to place. Aso-4 was distributed in clumps within the makado stone, and red and black areas were scattered in a complex manner. Furthermore, the lithology of the Makado stone and the surrounding Aso-4 was exactly the same except for the color of the Aso-4.
(4) Flake production and observation
With the cooperation of the Mifune-cho Dinosaur Museum, rock flakes were produced and observed. As a result, volcanic glass and porous voids, which are characteristic of tuff, were observed in both Makadoishi and Aso-4.
(5) Formation of Makadoishi
Based on these results, the formation of Makadoishi is comprehensively discussed. The red color of makadoishi is caused by Fe2O3. We considered that the part of the makadoishi that was deposited as pyroclastic flow and came into contact with incoming oxygen due to porosity under high temperature, produced Fe2O3 by high temperature oxidation and became makadoishi. The areas that did not get enough oxygen remained black Aso-4, and the red and black areas may be complex.
References.
[1] “Bamonishi: Touching the Trajectory of the Eruption,” Kumamoto Nichinichi Shimbun morning edition (June 13, 2021).
[2]Takada, T. (1969) Formation and Properties of Iron Oxide and Iron Hydroxide Compounds.
[3]Shumpei Misawa(1983) Iron Rust Formation: Current Status and Unresolved Issues
[4]Shigeru Suzuki(2008) Formation process and structural changes of iron rust
[5]Masataka Sugiyama(1959) High-temperature oxidation of metallic materials and its countermeasures
[6]Katsuya Inoue(1983) Various phases of iron oxides
[7]Geological Map of Kumamoto Prefecture (1:100,000) Kumamoto Prefecture Geological Map Compilation Committee(2008)
[8]Geographical Survey Institute Map
Makadoishi (Makado stone) produced in Umamon, Amizu-cho, Kumauzu City has a characteristic red color, but the reason for this color is unknown, so we decided to investigate the cause of the red color. From past literature[1] , we hypothesized that the cause of the red color was Fe2O3 (hematite), and began our research.
Research Contents
(1) Literature survey and experiments
(1) Literature survey and experiments (2) Density and magnetism are not significantly different, and the only differences are color and hardness.
(1) Literature survey and experiments
The red iron oxides are Fe2O3 and FeO(OH) [2][3][4].
When we conducted an experiment using iron nails, we found that Fe2O2 did not change even when heated with a gas burner, whereas FeO(OH) did.
In contrast, FeO(OH) formed orange rust in about half a day after being soaked in water, indicating that Fe2O3 requires higher temperatures to be formed.
OH, which is a kind of Fe2O3, was found to require higher temperatures for its formation.
Aso-4, magnetite, and hornblende were soaked in water and exposed to air for observation. Aso-4, magnetite, and hornblende were immersed in water and exposed to air.
Aso-4, magnetite, and hornblende were soaked in water and exposed to air, and no change was observed after several months.
(2) Component analysis and firing test
(1) X-ray fluorescence analysis and X-ray diffraction were conducted.
X-ray fluorescence analysis and X-ray diffraction were conducted.
(2) Compositional analysis and firing test (i) X-ray fluorescence analysis and X-ray diffraction were conducted.
(3) X-ray diffraction: The presence of Fe2O3 could not be clearly confirmed in any of the samples.
(2) Makado stone and Aso-4 were heated sufficiently at different temperatures (300°C and 1,000°C) for 24 hours using an electric furnace.
Firing experiment: Both samples heated at 1,000°C turned red.
It was considered that the iron in the rock changed to Fe2O3[5][6] and that the factor responsible for the color of the makado stone was the iron in the rock.
(3) Field survey
We considered the cause of the red color from the distribution[7][8].
We were able to confirm the boundary between the Bamon Stone and Aso-4 at several locations. The boundaries were scattered, with slopes varying from place to place. Aso-4 was distributed in clumps within the makado stone, and red and black areas were scattered in a complex manner. Furthermore, the lithology of the Makado stone and the surrounding Aso-4 was exactly the same except for the color of the Aso-4.
(4) Flake production and observation
With the cooperation of the Mifune-cho Dinosaur Museum, rock flakes were produced and observed. As a result, volcanic glass and porous voids, which are characteristic of tuff, were observed in both Makadoishi and Aso-4.
(5) Formation of Makadoishi
Based on these results, the formation of Makadoishi is comprehensively discussed. The red color of makadoishi is caused by Fe2O3. We considered that the part of the makadoishi that was deposited as pyroclastic flow and came into contact with incoming oxygen due to porosity under high temperature, produced Fe2O3 by high temperature oxidation and became makadoishi. The areas that did not get enough oxygen remained black Aso-4, and the red and black areas may be complex.
References.
[1] “Bamonishi: Touching the Trajectory of the Eruption,” Kumamoto Nichinichi Shimbun morning edition (June 13, 2021).
[2]Takada, T. (1969) Formation and Properties of Iron Oxide and Iron Hydroxide Compounds.
[3]Shumpei Misawa(1983) Iron Rust Formation: Current Status and Unresolved Issues
[4]Shigeru Suzuki(2008) Formation process and structural changes of iron rust
[5]Masataka Sugiyama(1959) High-temperature oxidation of metallic materials and its countermeasures
[6]Katsuya Inoue(1983) Various phases of iron oxides
[7]Geological Map of Kumamoto Prefecture (1:100,000) Kumamoto Prefecture Geological Map Compilation Committee(2008)
[8]Geographical Survey Institute Map