Igneous rocks form out of cooling lava or magma. Sedimentary rocks develop from eroded grains of other rocks and organic matter. Metamorphic rocks are the third main classification. These started ...

Hence, too, another problem, a corollary to the former, to frame a natural classification of igneous rocks, based on genetic principles, to supersede the provisional classifications on various ...

Igneous rocks close igneous rockIgneous rocks are those which have been formed by the cooling and solidification of molten rock (magma) from underneath the earth’s crust. are formed by magma ...