Nepheline, which is the most common of a group of minerals called feldspathoids, is a primary component of several igneous rocks, including ijolite. Presence of nepheline is often an indication that the rock in which it is contained is alkali-rich.

The crystalline rock ijolite is considered the plutonic analogue to olivine-poor nephelinites and nepheline dolerites. In addition to nepheline, it is chiefly composed of an alkali pyroxene mineral, but may also contain various other materials, such as calcite, sphene, melanite, wollastonite, and pectolite. Relatively rare, it may be found in Magnet Cove, Arkansas, Iron Hill, Colorado, the Kola Peninsula of Russia, and Canada’s Ice River, among other less well-known locales. Sometimes characterized as a type of gabbro, when ijolite does occur, it often appears as a component of carbonatite–alkali igneous complexes.