Koya Shimosaka

Bio: Koya Shimosaka is an academic researcher from University of Education, Winneba. The author has contributed to research in topics: Scanning electron microscope & Sepiolite. The author has an hindex of 2, co-authored 6 publications receiving 14 citations.

Classification of Clay Minerals

Abstract: 鉱物 の化学組成は,構 造式(単 位胞1/2)で 示 した。各鉱物の比較が容易にできるように構造 式は 『層間イオン』『8面 体層』『4面 体層』『陰 イオ ン類』に分割 して示 し,参 考までに各鉱物の 結晶系 も載せた。 一般に鉱物の構造式の記載 ,原 子価の小 さい 順 になっていることが多いようであるが,今 回は 可能な限 り各層に占めるイオン数の多い物から順 に記 した。主に,「Newman(1987)」5)を 参考にし た。 参考文献 は下に載せた。多 くの鉱物について調 べたが,鉱 物種によって,そ の分析値の信頼性が 著 しく異なっているようであるが,他 に比較でき る文献が手元 にないので,や むをえず,今 回はそ のデータを用いた。 原著論文 に目を通していないことや,今 後 より 詳細 なデータの公表によって,こ の分類表が訂正 され,よ り正確 になることを期待 している。 参考文献

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Abstract: The structure and chemical composition of sepiolite and palygorskite are known from the first half of the twentieth century. Ideal palygorskite Si 8 O 20 (Al 2 Mg 2 )(OH) 2 (OH 2 ) 4 ⋅H 2 O) 4 has dioctahedral character, and sepiolite Si 12 O 30 Mg 8 (OH) 4 (OH 2 ) 4 (H 2 O) 8 is a pure trioctahedral mineral. In the two minerals, isomorphic substitutions in both tetrahedral and octahedral sheets are frequent. In addition, Mg-rich palygorskites, Fe-rich palygorskites and Al-rich sepiolites have been reported and it seems that the compositional limits accepted until now could be too narrow. Therefore, sepiolite and palygorskite can be classified into different types depending on the composition. In this chapter, the variations in the chemical composition of natural sepiolites and palygorskites as well as the limit of chemical composition of both minerals, if it exists, using the data from the literature available are established. Sepiolite can be classified into two types: sepiolite and Al-sepiolite. A limit for these two types can be established from the octahedral occupancy, and Al-sepiolites are those that have more than 10% of octahedral positions vacant and more than 0.5% VI Al atoms. On the other hand, palygorskite is classified into Ideal palygorskite with an octahedral composition near to the ideal palygorskite. Common palygorskite : where VI Al content is less than in the ideal formula and as a consequence that the Mg content is higher, but the number of octahedral cations is close to 4. Magnesic palygorskite is the most trioctahedral extreme, and Aluminic-palygorskite , which is defined by a total number of octahedral cations (p.h.u.c.) 3 ) > Mg. Magnesic palygorskite and aluminic sepiolite can have very similar chemical composition. There is no a compositional gap between the two minerals. Palygorskite can be so rich in Mg and sepiolite so rich in Al that is possible to affirm that a continuous composition series exist and all the intermediate compositions between the two extremes corresponding to the two pure minerals can be found. The intermediate compositions can be explained by intergrowths of sepiolite and palygorskite ribbons or polysomes.

Sepiolite and Palygorskite in Japan

Abstract: Recent investigations on palygorskite and sepiolite from Japan are summarized in relation to their mode of occurrence and mineral genesis. Description of the Japanese palygorskites has been confined to only two specimens from the Kuzuu district, represented by “karst region” where a thick sequence of carbonate rocks crops out extensively. These two palygorskites occur along fissures or faults as fillings and are considered to have been formed by direct precipitation from an aqueous solution at earth-surface temperature. The solution rich in silica and magnesium with lesser amount of aluminium, resulted from the descent of meteoric water. Japanese sepiolites, on the other hand, show various modes of occurrence, and may be classified largely into four groups on the basis of their mode of occurrence; (1) sepiolite in serpentinite, (2) sepiolite associated with metallic mineral deposits, (3) sepiolite from the “karst region”, and (4) sepiolite (iron-rich variety) in Tertiary sediments. The sepiolites are considered to be of either hydrothermal or supergene origin, and to have been formed by direct crystallization from low-temperature hydrothermal solution and/or from supergene or marine water rich in silica, magnesium and other components. Palygorskite and sepiolite in Japan do not form sedimentary deposits of economical importance, and occur on a small scale. Intensive studies of clay mineral compositions in clay fractions of surface marine sediments in the oceans and seas in the environs of the Japanese Island Arc, have not confirmed so far the presence of palygorskite or sepiolite.

Chapter 1 An outline of clays and clay minerals in Japan

Abstract: Publisher Summary This chapter presents the studies on the clays and clay minerals of Japan. The chapter presents the research and discussion that includes: (1) the specific properties of clay minerals as revealed by X-ray; thermal, electron optical analyses, etc.; (2) some of the analytical procedures; (3) synthesis; (4) changes in the properties of clays and clay minerals on heating, grinding, and chemical treatment; and (5) miscellaneous items. The chapter surveys the mineralogical properties, modes of occurrence, and origin of the clays and clay minerals found in Japan. Throughout geological time, volcanic activity has frequently occurred in Japan, resulting in an abundance of clays and clay minerals that occur as hydrothermal alteration products of various rock types, and as weathering products of volcanic ashes and glassy tuffs. The chapter reveals the studies based on the exchange acidity (in modern terminology) confirming the release of alumina on treatment with neutral salt solution, and revealing the important role of alumina in the clay acidity.