Igneous rock containing a relatively high concentration of the alkali (lithium, sodium, potassium, rubidium, caesium, and francium) and alkaline earth metals (magnesium, calcium, strontium, barium, and radium). Both silica-saturated and silica-undersaturated varieties exist, expressed in the presence of alkali feldspars and feldspathoids respectively. Alkali ferromagnesian minerals are usually present, and their identity depends on the composition of the rock. Igneous rocks of the alkaline suite span the composition range from basic to acid, and may be intrusive or extrusive.