著者

鈴木 五百紀 秋月 瑞彦 長瀬 敏郎 藤巻 宏和

出版者

一般社団法人 日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.90, no.4, pp.124-131, 1995 (Released:2006-12-26)

参考文献数

42

被引用文献数

1 1

---

Orbicular rock from Inusotoba, Shiroishi, Miyagi Prefecture was studied by optical and chemical methods. The orbicules, which are 5∼20 cm in diameter, are divided into two parts, — core and shell. The core is ball-shaped and dark-colored, and consists mainly of fibrous hornblende and chlorite. The shell, which surrounds core, is light-colored and consists of coarse radial anorthite crystals less than l cm long, which are elongated to a-axis. These radial crystals are characterized by micro subgrains of albite twin and parallel-growing crystals. The other type of orbicule is also known, whose shell consists of several alternate layers of mafic and felsic minerals. This latter type of orbicules is never produced together with the former radial type. The matrix, solidified among orbicules, has a heterogeneous texture, which consists of the dark-part of poikilitic hornblende and the light-part rich in euhedral plagioclase.     The forming environment of orbicular rocks is featured by many close-packed orbicules, the flow structure of felsic mineral assembledge in matrix and unmixing of magma including orbicules with the other magma containing plagioclase spherulites. It is considered that orbicules were formed in supercooling magma possibly due to income of another magma.

著者

川上 紳一 金折 裕司 大野 照文

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.87, no.10, pp.393-411, 1992-10-05 (Released:2008-03-18)

参考文献数

127

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Soon after the formation of the Earth by collisional accretion of planetesimals in the primordial solar nebular, its interior has been differentiated gravitationally to form the central metallic core, silicate mantle and crust, atmosphere and ocean. The sequence of differentiation was very rapid during the formation and subsequent early history, since the interior has been maintained hot by the heating of accretional energy, gravitational energy of core-mantle separation and energy released by the radioactive neclides. The differentiation and interactions between the core, mantle, crust, atmosphere and ocean has been continued throughout the Earth's history less effectively but still a significant way. The mode of interactions between the subsystems of the Earth includes mass transfer (geochemical cycle), electromagnetic interaction, and mechanical interactions such as angular momentum exchange, tidal interaction and convective flows and plate motions. Since these interactions have been maintained by the energy of radioactive nuclides and solar energy, the Earth system can be regarded as disequilibrium dissipated system with highly non-linear behavior. Many rhythmical variations in the Earth environments such as climate change, sea level change, geomagnetic variation, plate velocities and orogeny, volcanic and seismic activities are expected to show signatures of the non-linear dissipative systems. Specifically we expect the period bifurcation phenomena revealed in many non-linear systems would exist in the rhythmical variations in the Earth's history. Here we reviewed the spectrum structures of galactic motions, solar activities, orbital motions of the Earth and planets with special reference to the Milankovitch cycles, the Earth rotatonal variation, geomagnetic variations, variations in the atmosphere and ocean phenomena, climate change, meteoroid impact and mass extinciton episodes, and then revealed nature of multi-sphere interactions in the Earth's history in the frequency domain. Some future problem to explore the nature and mechanisms in the multi-sphere interaction and evolution of the Earth were discussed.

著者

田崎 耕市 高橋 治郎 板谷 徹丸 グレープス R.H. 鹿島 愛彦

出版者

日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.85, no.4, pp.155-160, 1990

被引用文献数

10

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Many andesitic intrusions are exposed along the Median Tectonic Line (MTL) in northwestern Shikoku, Japan. Three dikes along the MTL and one intrusion occurring close to it were dated by the K-Ar method to estimate when the fault movement ceased. The dikes and intrusion are not deformed by the movement. The results give 15.1 to 15.4 Ma excluding severely altered one. The MTL in northwestern Shikoku region has not been active since about 15 Ma. Although a similar attenuation of active movement of the MTL during middle Miocene has been reported, the fault movement has continued in the other areas of southwestern Japan as demonstrated by Active Fault Research Group (1980). This may suggest that block displacement has been dominant since middle Miocene in the studied area. The age of the samples also indicates that the volcanic activity of Seto-uchi region started 15 Ma in northwestern Shikoku.

著者

張 永杰 吉村 尚久

出版者

一般社団法人 日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.92, no.9, pp.363-378, 1997 (Released:2006-09-22)

参考文献数

33

被引用文献数

1 1

---

南部丹沢山地に分布する安山岩質—玄武岩質火山岩類からなる中新世丹沢層群は,束沸石,濁沸石,ブドウ石—パンペリー石,緑れん石,緑れん石—角閃石及び角閃石帯に分けられる。これらの帯に産出するブドウ石,パンペリー石及び緑れん石のFe3+/(Fe3++Al)値は変成温度の上昇に伴い低くなり,一つのサンプルあるいは変成帯でも産状と共存鉱物によって,異なっている。グランダイトザクロ石が同定され,また,その形成条件が検討された。ブドウ石,パンペリー石及び緑れん石が高いFe3+値を示すことと赤鉄鉱+スフェンが広く出現することによって,変成時の高いfo2が推定される。高いFe3+値のブドウ石,パンペリー石及び緑れん石の安定条件はfo2に強く支配されることから,ブドウ石—パンペリー石帯から角閃石が出現しない緑れん石帯への転換が解釈できる。

著者

氏家 治 田中 るみ 渡邊 和徳

出版者

日本鉱物科学会

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.94, no.9, pp.315-328, 1999-09-05

参考文献数

41

被引用文献数

7 8

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毘沙門岳火山は単斜輝石&mdash;斜方輝石安山岩&sim;デイサイトと比較的少量の角閃石安山岩からなる。Sr/Y>40, SiO₂&asymp;63%, Al₂O₃&asymp;18%の組成を有するこれらの岩石はアダカイト質であり,近隣の火山の岩石と比べてK₂O, Rb等の液相濃集成分に乏しく,基本的には,広域的安山岩マグマと当火山に固有の珪長質マグマの混合物と考えられる。珪長質端成分マグマは,Mgに富む斜方輝石(Mg/(Mg+Fe)&asymp;0.80),単斜輝石(Mg/(Mg+Fe)&asymp;0.82)恐らくマントル由来の橄欖石(Fo&asymp;90)を特徴的に含み,その化学組成(SiO₂>65%, Na₂O&le;3.2%, K₂O&le;1.2%, Rb&le;20 ppm, Y<10 ppm, Nb&le;6 ppm,全FeO/MgO&le;1.6,およびSr/Y>60)はアダカイトの特徴をより明瞭に示す。断定するには未だデータ不足だが,この端成分アダカイトマグマは沈み込みつつあるフィリピン海プレート海洋地殻の部分溶融作用で生じた可能性が高い。

著者

飯塚 義之

出版者

一般社団法人 日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.91, no.3, pp.73-85, 1996 (Released:2006-12-13)

参考文献数

22

被引用文献数

2 1

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Komochi volcano (1,296 m), located at the southernmost part of NE Japan arc, is a Quaternary composite volcano with a diameter of approximately 6 km and a volume of approximately 10 km3. The basement is composed of the Kirigakubo Formation, a member of the Miocene rhyolitic tuff formation, and Iwamoto volcanoes, dacite lava domes (ca. 6 Ma). The rocks of the Komochi volcano consist of low-K andesites with small amounts of basaltic andesite and dacite. All rocks of the Komochi volcano belong to the hyperthenic rock series. The volcanic activity of the Komochi volcano can be divided into following three stages: Ayado stage (c.a. 1.6 Ma), Early Komochi (0.9 Ma-) and Late Komochi (0.6-0.2 Ma) volcano stages which is subdivided into the two kinds of activities: stratovolcano-forming and lava dome-forming. At any stage, a large number of andesitic dikes intruded, which comprise radial dike swarm in the circumference of the Daikokuiwa neck. The Komochi volcano has a life span of about 1.4 m.y. and calculated production rate of 0.14-0.25 km3/104 yr., which is very small compared to lager volcanoes around Komochi volcano, for example Myoko and Hakone volcanoes, and even smaller than similar volcanoes in the Shin-etsu Highland area.

著者

朽津 信明

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.87, no.9, pp.388-391, 1992

被引用文献数

7 2

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Evaporites were observed on a surface of the historical brick in the Museum Meiji-Mura. Aphthitalite (K₃Na(SO₄)₂), thenardite (Na₂SO₄), trona (Na₃H (CO₃)2•2H₂O), and thermonatrite (Na₂CO3•H₂O) were identified as the main component minerals of the evaporites. These evaporates are considered to be formed in these less than a few decades under the humid climate of Japan. Because no sulfur-containing minerals can be found in the plaster nor in the bricks, it is thought that aphthitalite and thenardite were formed by the interaction between bricks and acid rain water with SO₄^2-ion. Experimental results support this idea; rain water-brick interaction has produced sulfate, whereas distilled water-brick interaction has not produced sulfate. To conserve this brick cultural property, it is desirable that roofs and gutters would be improved to prevent bricks from impregnation of rain water.

著者

坂野 靖行

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.92, no.5, pp.189-194, 1997-05-05

参考文献数

17

被引用文献数

2

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四国中央部猿田川地域の三波川変成域から得られた石英片岩中の角閃石のコアに含Mnウインチ閃石(MnOとして最大4.19 wt.%)が見出された。石英片岩の構成鉱物は石英,曹長石,角閃石,白雲母,ざくろ石,緑泥石,褐れん石,方解石,燐灰石,スティルプノメレン,電気石,赤鉄鉱,黄鉄鉱である。角閃石は自形から半自形で,最大長径700 μmである。角閃石のコアの組成は,バロワ閃石からウインチ閃石をへて含Mnウインチ閃石まで変動する。角閃石のリムはアルカリ角閃石(主にマグネシオリーベック閃石)とウインチ閃石である。石英片岩中のざくろ石はスペッサルティン成分に富む(59-79%)。

著者

池田 圭一 早坂 康隆

出版者

日本岩石鉱物鉱床学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.89, no.12, pp.454-464, 1994-12-05 (Released:2008-03-18)

参考文献数

26

被引用文献数

6 13

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Rb-Sr isotopic age determinations were made on the basement rocks of the Northern subzone of the Maizuru Terrane in the western Maizuru City and Oe Town area. The rocks of the area consist mainly of granitic rocks with minor amounts of quartz-diorite, gabbro, diabase, and pelitic schist and amphibolite (Komori metamorphic rocks), being called the Northern Yakuno rocks. They are distinguished from the Southern Yakuno rocks which consist of ophiolitic complex (Yakuno ophiolite) lying in the Southern subzone of the terrane by their lithofacies and whole rock chemistry. The Northern Yakuno rocks are characterized by the abundance of K-feldspar rich granitic rocks, whereas the Southern Yakuno rocks do not contain such rocks. The Northern Yakuno rocks are thrust over the Shimomidani Formation of the Akiyoshi Terrane to the north in the area. The Rb-Sr mineral isochron ages were determined upon six granitic rocks and one quartzdiorite. They can be divided into two age groups, the older (around 300 Ma) and the younger (around 150 Ma). The rocks give whole rock isochron ages of 327 Ma for the older group and 149 Ma for the younger one, whose initial 87Sr/86Sr ratios are 0.70669 and 0.70779 respectively. Whole rock isochron age for the gabbros and diabases is 163 Ma, and initial 87Sr/86Sr ratio is 0.70687. Nearly coincidence between whole rock and mineral isochron ages for each age group explains the existence of two stage igneous activities at those ages in this area, despite their mylonitization and recrystallization. Both whole rock chemistry and the initial 87Sr/86Sr ratio of those rocks indicate that the Northern Yakuno rocks was evolved as an matured crust of island-arc or continent by the late Carboniferous time. In this respect, the evolutional history of the Northern subzone is quite different from that of the Southern subzone in the terrane.

著者

林 正雄

出版者

日本岩石鉱物鉱床学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.84, no.5, pp.152-158, 1989-05-05 (Released:2008-03-18)

参考文献数

5

被引用文献数

2 1

---

A method is proposed to describe quantitatively various zircon crystal forms projected either on the plane {100} or {110}. When the crystal planes observable from one direction are assumed to be the same size as those on the opposite side, four indexes can be calculated: the flatness index is the ratio of the total thickness to the total width, the elongation index is the ratio of the prism height to the sum of the total height and the total width, the prism index is the ratio of the total width of {100} to the prism perimeter, and the pyramid index is the ratio of the pyramid height to the height of {211}. All these indexes range from 0 to 1 for almost all zircon, and, regardless of the direction of observation, they remain virtually unchanged. This technique will provide useful clues not only to correlate igneous formations but also to estimate the physico-chemical conditions of the host rock of zircon crystals.

著者

内田 悦生 前田 則行 中川 武

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.94, no.5, pp.162-175, 1999-05-05

被引用文献数

3 23

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アンコール遺跡に使用されている主要石材の一つであるラテライトの研究を行った。調査はアンコール遺跡の主要25遺跡において行った。<br>   アンコール遺跡に使用されているラテライトはその組織によりピソライト質ラテライトと多孔質ラテライトとに分けられる。その主要構成鉱物はどちらも同じであり,針鉄鉱,赤鉄鉱,カオリナイトおよび石英である。<br>   調査した25遺跡は,使用されているラテライトの孔隙サイズと帯磁率に基づき5つのグループに分けられる。ただし,プノム・クロムとバンテアイ・スレイは例外である。この分類は微量元素であるAs, Sb, SrおよびVの含有量からも裏付けされる。このことはラテライトの石切り場が時代とともに変化したことを示している。<br>   ラテライト材の層理面方向を調査した結果,層理面が縦になっている石材の割合はアンコール・ワットより前の建造物では高いが,アンコール・ワット以降の建造物ではその値が低くなっている。このことは,アンコール・ワット以降では層理面方向を意識して建造が行われたことを示している。<br>   プラサート・スープラとクレアンに隣接する池は,その護岸に使用されているラテライトの孔隙サイズ,帯磁率,層理面方向および微量元素の含有量からクレアンと同じ時代に建造されたと推定される。

著者

大場 司

出版者

日本岩石鉱物鉱床学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.88, no.1, pp.1-19, 1993-01-05 (Released:2008-03-18)

参考文献数

15

被引用文献数

5 9

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Magmatic evolution of Akita-yakeyama volcano, northeastern Japan, has been investigated based on bulk chemistry (major and trace), Sr isotopic features and mineral chemistry in combination with stratigraphical study. The main body of the volcano was built by eruptions of a large amount of hypersthene-augite andesite magma and a minor amount of olivine bearing hypersthene-augite andesite magma as lava flows and pyroclastic falls, and an edifice of stratovolcano was built. No evidence of magma mixing or crustal assimilation can be recognized in the olivine free andesite, but olivine-pyroxene disequilibrium in the olivine bearing andesite indicates magma mixing. After a repose period, a series of eruptions began from the central vent and erupted hypersthene-augite andesite magma as fine ash fall and hypersthene-augite-olivine andesite magma as lithic-rich pyroclastic falls. As stated above the olivine-free andesite has no evidence of magma mixing, but the olivine bearing andesite has the mineralogical and chemical evidence of magma mixing, such as disequiliblium phenocryst assemblage, reverse zoning of pyroxene and dusty plagioclase. Flank eruptions followed and erupted quartz bearing olivine-hypersthene-augite andesite magma, quartz bearing augite-hypersthene andesite magma and augite-hypersthene dacite magma as lithic-rich pyroclastic falls, lava flows and pumice fall. Among them quartz bearing andesites have high 87Sr/86Sr ratios, suggesting the involvement of crustal assimilation. At the end of these eruptions, augitehypersthene dacitic lava dome and olivine bearing augite-hypersthene dacitic lava dome intruded into central crater. Dacite magma of the lava domes has no or little evidence of magma mixing or crustal assimilation. Chemical variation of trace elements (Zr, Rb, Y) from the hypersthene-augite andesite of the main body to the augite-hypersthene dacite of the domes cannot be accounted for by fractional crystallization, and difference of degree of partial melting of the source material is required.

著者

村上 英樹 木股 三善 下田 右 伊藤 英司 佐々木 聡

出版者

日本岩石鉱物鉱床学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.87, no.12, pp.491-509, 1992-12-05 (Released:2008-03-18)

参考文献数

37

被引用文献数

2 8

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合成された純粋な灰長石,それぞれMgO, SiO2に富んだ灰長石を, EPMAと四軸自動X線回折装置を用いて化学組成と格子定数の測定を行い,三宅島産灰長石との比較を行った。複合イオン置換に基づく検討から,天然及び合成の灰長石は, MgをCaMgSi3O8, 過剰のSiは ?? Si4O8端成分として,固溶する可能性が指摘された。さらにMgに対するこの端成分を確認するため, EPMAによるMgの化学シフトを解析した。その結果,合成灰長石に固溶されるMgは,オケルマナイト(Ca2MgSi2O7) 中のMgと同じ四配位席を占有することが示唆された。また, X線単結晶回折法からは, Mgの固溶量が増加するに従って,単位格子の体積が増加する傾向が明らかになった。以上のことから灰長石におけるMgの固溶は,雲母,角閃石,輝石に認められる通常のTschermak置換, Mg+Si ?? ;2Al, とは異なり,四配位席だけでのTschermak置換が,メリライトと同様に灰長石においても成立することを明示している。

著者

モリス ポール 三宅 康幸 古山 勝彦 ペレス パブロ

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.94, no.11, pp.442-452, 1999-11-05

被引用文献数

4 5

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島根県東部中海の若い盾状火山である大根島の玄武岩について全岩の主要元素・微量元素·同位体組成を分析した。K-Ar年代は第四紀の約20万年前の噴出を示している。層準ごとのサンプルの化学組成の変異は,これらがすべて同一の玄武岩質親マグマ(100 Mg/(Mg+Fe)∼56, Ni 101-160 ppm, Cr 110-226 ppm)からの分化物であることを示している。SrとNd同位体組成からは,全地球組成に近い均一な起源物質が示される。初期のマグマは後期よりも低い溶融程度で生じ,より若い溶岩の間の化学的変異は,異なる溶融程度といくらかの地殻物質混合とにより説明される。

著者

山田 涼子 佐藤 博明

出版者

一般社団法人 日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.93, no.8, pp.279-290, 1998 (Released:2006-08-22)

参考文献数

34

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Takamatsu crater has been identified and named by Kono et al., (1994), based on the presence of a concentric gravity low in the southern part of Takamatsu Plain, northeast Shikoku, Japan. The crater is 1∼2 km deep and ca. 4 km across, and buried under the Miocene volcanic formation and alluvium deposit. Both impact and volcanic origins have been proposed for the crater, but remained unresolved. We searched for the evidence of impact origin of the Takamatsu crater, such as shock metamorphic features of minerals, variable and extraordinarily high contents of SiO2, FeO, and NiO, together with low Na2O content of fresh glass in the Miocene deposit. The glass fragments in the pyroclastic flow deposit in the southern part of the Takamatsu crater are characterized by xenocrysts of quartz and feldspar and lack of idiomorphic phenocrysts. We did not find evidence for shock metamorphism in the minerals. The glass shows heterogeneous appearence with variable red tints and high vesicularity under the microscope, somewhat similar to the suevite of Ries crater. The glass of the Takamatsu crater, however, shows uniform and rhyolitic chemical composition, which is common for the calc-alkalic volcanics of the Miocene Setouchi volcanic suite. Furthermore, chemical composition of the glass is almost identical to those of welded tuff blocks and bulk matrix of the pyroclastic flow deposit, indicating that the glass fragments are of volcanic origin. The glass and associated rhyolite are dated by K-Ar method at around 14 Ma, which coincides with the age of the Setouchi volcanic activity. Although deep drilling has not been carried out for determining the subsurface structure, present analytical results argued for cauldron origin of the Takamatsu crater.

著者

伊藤 俊彦

出版者

日本岩石鉱物鉱床学会

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.91, no.6, pp.209-219, 1996-06-05

被引用文献数

1

著者

伊藤 俊彦

出版者

日本鉱物科学会

雑誌

岩鉱 (ISSN:09149783)

巻号頁・発行日

vol.91, no.6, pp.209-219, 1996 (Released:2006-11-25)

参考文献数

22

被引用文献数

8 27

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氷点下の気温になる冬季間,北海道足寄町螺湾のシオワッカ冷泉からの弱い流れの中で,ikaiteが生じている。積雪の少ない年には,氷に閉じこめられた産状でikaiteからなる輪縁石ダムが見られた。海洋,湖沼以外である流水域におけるikaiteの生成はこれまでは知られていない。先年の夏に同地域から,calciteといっしょにmonohydrocalciteの生成が知られたところから,冬のikaiteの生成が予想された。シオワッカ冷泉石灰華からはikaiteからの転移鉱物のvateriteを加えると,aragoniteを除き,自然界での炭酸カルシウム塩鉱物のほとんど全てが得られた。本地における夏から冬の間の炭酸カルシウム塩鉱物の生成の過程を,産状から考察した。これらの鉱物の生成における必要条件は,水質のほか,水温(ikaite,calcite),地表面の濡れ(monohydrocalcite:伊藤,1993),など,それぞれによって異なる。また,シオワッカ冷泉の水質,ikaiteおよびvateriteのX線粉末回折線値,ikaiteから転移した後の方解石の化学組成を示した。     Ikaiteが冷たい海域,深海堆積物から次々と発見されたことから,1982年来,これまで源鉱物の明らかでなかったglendoniteや玄能石と呼ばれてきた方解石仮像の源鉱物がikaiteであるとする説が多く出されてきた。しかし,ikaiteの結晶形と一般的な大きさはこれまでに知られている方解石仮像と一致しない。ここでは,方解石仮像に特徴的な四角錐に対応する結晶形が,走査型電子顕微鏡で観察されたikaiteの結晶面の組み合わせによって導かれることを示した。Ashoro-cho 足寄町,Rawan 螺湾,Shiowakka シオワッカ,Konbumori 昆布森