Metaluminous rock
{{Short description|Type of igneous rock}}
Metaluminous rocks are igneous rocks that have a molar proportion of aluminium oxide lower than the combination of calcium oxide, sodium oxide and potassium oxide.{{cite web|url=http://www.encyclopedia.com/doc/1O13-metaluminous.html|title=metaluminous – Dictionary definition of metaluminous | Encyclopedia.com: FREE online dictionary|publisher=encyclopedia.com|accessdate=2016-04-14}} This contrasts with peraluminous rocks in which the aluminium oxide concentration is higher than the combination, and peralkaline rocks where the alkalis are higher. Most mafic rocks are metaluminous, having neither excess aluminium nor alkalis.{{cite book |last1=Frost |first1=BR |title=Essentials of igneous and metamorphic petrology |publisher=Cambridge University Press |pages=58}} In such rocks the alkalis are mostly accommodated in feldspars, and the remaining calcium and minor sodium are found in hornblende and augite.