天然ゼオライトの結晶成長 : 表面マイクロトポグラフの観察

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Decoration-method, which was newly developed as original technique, was applied to the examination of surface microtopographies for diagenetic clinoptilolite. Natural materials were treated in a weak alkaline solution of Na_2CO_3 at a range from 150 to 200℃. Fine particles of silica in the solution deposit along the steps on the crystal faces and decorate the original growth steps. The particles develop largely by a gold evaporation operation in vacuum and can be observed the crystal growth spirals by scanning electron microscope. Clinoptilolite specimens were obtained from Miocene dacitic tuff at two localities, Oga and Futatsui, Japan. All the crystals observed show spiral patterns on the (010) face, though other faces exhibit no growth pattern. The crystal distinctly are decorated along the spiral steps, and the height of steps is assumed to be that of unit-cell size. The patterns of Oga specimens are rectangle correlating to a orthorhombic symmetry. Some spiral patterns have square pits which are attributable to the dislocation site on the center. The patterns of Futatsui specimens have no etch pits, and vary from polygonal to circular. Many growth centers are observed on the (010) face, and the patterns are more complicated as compared with that of Oga specimens. Generally, polygonal spirals are expected under low temperature and low supersaturation conditions than for circular spirals, and also narrower step separations are expected for crystals grown from higher supersaturation. Geological evidence shows that the present zeolite crystals were formed under hydrothermal condition. It is suggested that Futatsui clinoptilolite crystals were produced under higher temperature and higher supersaturation condition than Oga specimens.
日本粘土学会の論文
1986-06-05

天然ゼオライトの結晶成長 : 表面マイクロトポグラフの観察

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