igneous rocks<span> can be "primary" rocks because they crystallize from a liquid. Sedimentary and metamorphic rocks </span>Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained Volcanic rocks, especially felsic and intermediate, often have a porphyritic<span> texture characterized by visible crystals floating in a fine-grained groundmass.</span>
