Igneous rocks, which are grouped into intrusive and extrusive, solidify from a partially or fully molten state. Extrusive rocks normally have a fine-grained texture due to rapid cooling of magma when subjected to the surroundings. Some examples are andesite, basalt and rhyolite. Magma that solidifies underground form intrusive rocks. Some examples are diorite and granite.
Metamorphic rocks refer to ones that were changed due to pressure, heat or chemical reaction of gases or fluids. The structures are classified as either nonfoliated or foliated. The nonfoliated type has a planar structure, while the foliated type is huge but structureless. Examples of the former are gneiss and slate, while examples of the latter are marble and quartzite.Learn more about Earth Science