Ultrapotassic igneous rocks

Ultrapotassic igneous rocks are a class of rare, volumetrically minor and generally ultramafic or mafic silica-depleted igneous rocks.

Ultrapotassic rocks are defined by molar K₂O/Na₂O >3 in much of the scientific literature. In other papers written as recently as 2005, they are defined as rocks with weight percents K₂O/Na₂O >2. Hence, caution is indicated in interpreting use of the term "ultrapotassic", and the nomenclature of these rocks continues to be debated.