Abstract
The weathering processes of minerals contained in decayed andesitic breccia sampled near the Horomi pass of Sapporo city were studied. Analytical technigue, was such as microscopic obsorvation. X-ray diflraction and electron microscopic observation.
The results were as follows.
1. In early stage of weathering process, Al-vermicullite rich in aluminun is formed from chrolite occured in decayed andesite. At the same time, plagioclase begins begins to alter to holloysite through albite.
2. In top horizon, regarded as most proceeded in soil formation, Al-vemicullite and kaoline minerals are found easily, along with some illite, halloysite and illite-montmorillonite mixlayered minerals.
3. Fabric and Organization of original rock are recognized only in lower horizons.
