In junior high school, the students learn to observe igneous rocks, including plutonic and volcanic rocks. Igneous rocks exemplified in the textbook are only those of typical specimens. However, rocks, either igneous, sedimentary or metamorphic rocks, observed in the field are sometimes weathered and show various lithologies. In order to make it possible to correctly identify igneous rocks, it is necessary to correctly recognize both their textures and structures and their rock-forming minerals, rather than to learn the rock name and its photo solely on a one-to-one basis. Taking granites as an example, introduced are: (a) the distribution of the main granite bodies observed in Western Japan; (b) their lithologies and (c) their formation ages.

本研究はJSPS 科研費JP22300272の助成を受けたものである。