In fluor-tremolite, fluor-phlogopite and topaz, the Si-O distances, where the oxygens are bonded to the non-tetrahedral ions containing fluor ions, are longer in comparison with those in no-fluorine compounds. This is caused from the decreasing of the π bonding between silicon and oxygen affected by the electronegative fluor ion.

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The characteristics of under ground water flow related to the weathering of granite are studied with the following results:
(1) The pattern of seepage path in weathered granite can easily be observed by means of the liquid penetrant method.
(2) An equation which is used to estimate the flow velocity in weathered granite is obtained by theoretical and experimental considerations.
(3) Numerical calculations of Navier-Stokes formula are useful to study the behaviors of flow in a micro crack in weathered granite.
(4) When water flows within the weathered granite, a kind of wake bubble tend to be formed near crack walls.

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Hydrothermally altered volcanic rocks are widely distributed in the Otsuka district, Hitoyoshi City, Kumamoto Prefecture. These altered rocks can be divided into two zones based on the clay minerals contained. They are smectite zone (Zone I) and mixed-layer mineral with kaolinite zone (Zone II). Zone I is a weakly altered area characterized by existence of smectite, and Zone II is characterized by a regularly interstratified smectite/illite and kaolinite. Many specimens of mixed-layer mineral found in this area have 30-35% of smectite layer, whereas specimens of mixed-layer mineral in quartz veins and rocks affected by silicification in the Zone II have 45-50% of smectite layer. The mixed-layer mineral was probably formed from smectite under a certain hydrothermal condition.

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Jeju Island which belongs to the Circum Japan Sea Alkali Rock Province is situated at about 90km the southern of Korean Peninsula. Its shape is an ellipe with size of 80×40km², and it is characterized by symmetrical form whose peak is Mt. Halla (1950m). It is shield volcano formed by central eruptions, neighborhood of Mt. Halla may be acted as eruption centers, during Upper Pliocene to Lower Pleistocene age, and they have erupted in historic time. Landform of this island can be divided into lava plateau, shield shaped Halla volcanic edifice and parasitic scoria cones more than 360, accoring to topographically.
It is composed chiefly of voluminous, thick basaltic lava piles, and accompanied with less abundant pyroclastic rocks. Hyaloclastite also occurs in small amount on coastal line.
Volcanism of this island can be classified into 4 stages, which are further subdivided into 19 stratigraphic units.
The stage 1 began with eruption of basaltic lava which contains olivine phenocryst and formed basement as a plateau from the marine floor to sea level. Pyroclastic sedimentary rocks composed of an alternation of shale, tuffaceous sandstone and fossil-shell are intercalated between stages 1 and 2.
The stage 2 commenced with eruption of basaltic lava distributed as forming a lava plateau, which is the most abundant in volume. It is similar petrographically to basaltic lava of the stage 1. During this stage, lavas change from basalt through trachyandesite to trachyte with decreasing its volume. Pyroclastic sedimentary rock contained fossil-shell is exposed between the stages 2 and 3.
The stage 3 formed shield shaped Halla volcanic edifice whose peak is about 2000m in height, and finally maked Backlockdam crater (400m in diameter) which is petrographically built up of two walls: basaltic and trachytic lavas. During this stage, lavas change from basalt to trachyandesite or to trachyte with decreasing its volume, repeatedly. Therefore, this stage can be further divided into 3 substages. The lava flows are characterized by plaigoclase and clinopyroxene phyric.
The stage 4, final activity, produces more than 360 parasitic scoria cones which mostly distributed on the vicinity of long axis of this island, most of which consist of pyroclastic material but rarely do basaltic and tracyandesitic lava flows.

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