Fill in the Blanks Igneous Rock SummaryOnline version A summary of some of the major learning concepts associated with Igneous rocks. by Kate Maccoll 1 pumice small flows bubbled felsic granite mafic Batholiths magma Large magma sills mineral moisture basalt melted flows on less craters size surface lava more 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 .