Application of image analysis to observe microstructure in sandstone and granite

Advanced techniques are examined to observe microstructure of rocks using i mage analysis combined with methods such as the fluorescent approach and th e application of optical characteristics of minerals. Analyzed are discrimi nation of grains in rocks, distribution patterns of grain orientation in sa ndstone, changes of grain shape as weathering advances and distribution pat terns of microcracks in granite. In Shirahama sandstone, relatively large a nd flat grains are orientated parallel to the bedding on the plane perpendi cular to the bedding, while grains on the plane parallel to the bedding sho w random patterns. In weathered granite, it is clarified that the grain sur face becomes complex as weathering advances and differences among three maj or mineral species are identified. In Inada granite, intracrystalline crack s predominate over intercrystalline cracks and.-rain boundary cracks both i n total length and number. Furthermore, three types of microcracks show dif ferent orientations; the intercrystalline cracks show a dominant orientatio n which coincides with the orientation of the rift plane, the easiest plane to split, while the intracrystalline cracks and grain boundary cracks show no preferred orientation.