Kurogaki (Black persimmon; Diospyros kaki) grows very slowly and has extremely hard wood known for its striking black coloration, referred to as the “peacock pattern”. It was formerly planted in Kanazawa, Ishikawa, Japan. Kurogaki is currently very rare, found in only one of every 1,000 to 10,000 trees. Therefore, scientific data on Kurogaki are currently very limited but these trees are highly valuable for manufacturing furniture, tea ceremony goods, boxes, and other miscellaneous articles.
Here we report the characterization of Kurogaki at Kanazawa, Ishikawa, Japan, based on radioactivity, purple mineral light, and H₂ O₂ reactions in the field. To date, no report has described the results of electron microscopy observations and chemical analyses, which could elucidate simple identification of species. Here we studied the microstructure, mineralogy, chemical composition, and radioactivity associated with microorganisms in Kurogaki wood using analytical data based on X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma-mass spectrometry (ICP-MS), imaging plate (IP), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), and semiconductor detectors. We investigated the distribution, location, identification, structure, and differentiation of the black “peacock pattern” parts and ordinarily colored wooden parts and roots.
We evaluated the mineralogy, chemistry, and micromorphology of Kurogaki using a combination of micro techniques. Using XRD, the black “peacock pattern” parts were found to mainly comprise cellulose associated with spherical and beaded microorganisms, mineralized living apatite, α-cristobalite, and halloysite. Particular elements associated with microorganisms were identified using SEM-EDS, which revealed the elemental content maps of the central white spot in cross sections of the “peacock pattern”, indicating high concentrations of Ca, P and S. The chemical compositions of the black and white parts were determined based on mineralogical and chemical data obtained using XRF analyzer and ICP-MS.
Furthermore, we used imaging plate methods to obtain radioactive images of the cross sections of the “peacock pattern”. The objective was to illustrate the association of minerals with various microorganisms that are capable of absorbing both radionuclides and stable isotopes from soil and water. A radio dosage analysis of the higher black parts was performed by imaging plate pictures. We investigated the quantitative radiation dosages of the “peacock pattern” using Ge and Si semiconductor detectors, which revealed ¹³⁷Cs concentrations.
The black “peacock pattern” parts were richer in almost all elements such as K, Ca, Mg, S, Al, Fe, P, Na, Mn, B and Ba, than the white cellulose parts, indicating a role of microorganisms in mediating the transfer of metal solutes from the hydrosphere and soils. Using SEM-EDS micromorphology, the chemical composition of the black “peacock pattern” parts was found to be associated with α-cristobalite and living apatite having wooden clapper-like microcrystals. The distribution of elements indicated the influences of soils in their surrounding environment. Our results provide the evidence of the ability of microorganisms to immobilize radionuclides in the soils. The microorganisms grow in the black “peacock pattern” parts of Kurogaki.
In conclusion, α-cristobalite and living apatite crystals physically and biologically grow in the sap with cellulose under neutral conditions (pH7) in association with microorganisms using carbon dioxide supplied by bacteria. Therefore, the crystals produced the “peacock pattern” in Kurogaki were formed at late times during the year.

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On November 22, 2014, an earthquake (M6.7) occurred in the northern part of Nagano Prefecture, central Japan. The JMA seismic intensity of 6 lower was recorded in Nagano City, Otari and Ogawa Villages. Damage of the building is as follows: The number of completely destroyed was 81, half destroyed was 162 and partially destroyed was 1,818. Seismic damage has occurred in Nagano City, Iizuna Town, Shinano Town and Ogawa Village as well as Hakuba and Otari Villages around the epicenter.
We have begun investigating of the earthquake damage in Nagano City, Iizuna Town, Shinano Town and Ogawa Village from immediately after the earthquake. Distribution maps of the seismic damages were made on the basis of our research data and the seismic damages data that were provided by Nagano City Office, Iizuna Town Office and Ogawa Village Office. As a result, in east of the epicenter, remarkable damage by ground motion revealed that occurred in a wide region spanning 30 km. In the east side of the Hakoshimizu to Asakawa districts which is located on the west side of the edge of the Nagano Basin, it was also revealed that the earthquake damage is sharply reduced. In addition, by utilizing such existing geological maps and landslide distribution maps, it was also examined the relationship between earthquake damage and topographical-geological features.

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The Kakuda Massif and the Mineoka Hill are situated in the Western Margin of the Echigo Plain, where underlain by the Miocene volcanic rocks and the Plio-Pleistocene sediments. The Mineoka Hill are isolated from the foot of the Kakuda Massif by low lands. The Echigo Plain Western Fault Zone runs around there, so it is feared that next big earthquakes will surely occur. The compilation of the geotectonic history in the Mineoka Hill leads to the activated history of its fault zone. It would suggest us to consider the next quakes. The geotectonic history in the study area is as follows.
Takenomachi Stage (Plio-Early Pleistocene): Shallow to bathyal sea environment. Fusube-Tojima Stage (Middle-Latest Pleistocene, 145±40 ka): Uplifting of the Kakuda Massif generated the Echigo Plain Western Fault Zone and the Mineoka Hill. Nika Stage (Earliest-Late Pleistocene, 106±39 ka): Continuity of the uplifting of the Kakuda Massif and the block faulting at the Mineoka Hill. Shallow sea to delta environment. Post-Nika Stage (Late Pleistocene to Recent): Powerful uplifting of the Kakuda Massif formed the “Mineoka Isolated Hill” and the Echigo Plain Western Fault Zone.

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