Lava Molten or partially molten rock material and dissolved gases. Lava is molten rock which has erupted at Earth's surface. Texture is an umbrella term which includes different aspects of how rocks look. Grain size is directly related to the conditions under which the rocks formed. Intrusive rocks cool slowly because they solidify inside the Earth.
Extrusive rocks cool rapidly because they solidify at Earth's surface.
Igneous rocks are also classified by their chemical compositions. Darker than felsic, lighter than mafic. Usually dark-colored, but high olivine content can lend green colors. Other rare colors can be found. As you know, there are three types of plate boundaries.