Completar frases Igneous Rock SummaryVersión en línea A summary of some of the major learning concepts associated with Igneous rocks. por Kate Maccoll 1 surface felsic magma flows more small craters on mafic less mineral flows Batholiths granite melted sills size Large moisture magma pumice bubbled lava basalt Rocks are classified by crystal and by content . Light coloured , high - silicon minerals called form from viscous magma . Darker coloured , lower silicon , higher iron and magnesium minerals called form from viscous magma . Molten material is liquid or partially rock . Molten material found below the of the Earth is called ; the surface is called . crystals form in rock , which cools slowly underground ; these include , gabbro and peridotite . , dykes and are rock formations that are created when cools underground . Cooling on the surface is rapid and results in the crystals of , rhyolite and andesite . Lava move over ground , which is off with other gases leaving the aerated textures of , scoria or vesicular basalt . Fragmented bits of rock and ash can fuse together while cooling to form tuff . Other surface igneous - rock formations include and lava .