[1] The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known.

They are distinguished from syenites not only by the presence of nepheline but also by the occurrence of many other minerals rich in alkalis and in rare earths and other incompatible elements.

In nepheline syenites, alkali feldspar dominates, commonly represented by orthoclase and the exsolved lamellar albite, form perthite.

Sodalite, colorless and transparent in thin section, but frequently pale blue in the hand specimens, is the principal feldspathoid mineral in addition to nepheline.

Other minerals common in minor amounts include sodium-rich pyroxene, biotite, titanite, iron oxides, apatite, fluorite, melanite garnet, and zircon.

A great number of interesting and rare minerals have been recorded from nepheline syenites and the pegmatite veins which intersect them.

There is high-grade metamorphic rock originated from nepheline syenite that is characterized by gneiss texture of very rare occurrence.

According to the IUGS classification nomenclature (International Union of Geological Sciences, Streckeisen, 1978), nepheline syenite has 10% < F/(F + A + P) < 60% and P/(A + P) < 10% (where F – feldspathoids, A – alkali feldspar, and P – plagioclase volume fractions).

Magmas of such rocks are formed in a variety of environments, including continental rifts, ocean islands, and supra-subduction positions in subduction zones.

Nepheline syenites and phonolites occur, for example, in Brazil, Canada, Cameroon, China, Greenland, Italy, Norway, the Pyrenees, Sweden, the Transvaal region, the Ural Mountains, in the USA Magnet Cove igneous complex of Arkansas, the mountains of the Central Montana Alkali Province,[2] and as well as on oceanic islands.

In the Americas these rocks have been found in Texas, Arkansas, New Jersey (Beemerville Complex[4]) and Massachusetts, also in Ontario, British Columbia and Brazil.

Rocks of this class also occur in Brazil (Serra de Tingua) containing sodalite and often much augite, in the western Sahara and Cape Verde Islands; also at Zwarte Koppies in the Transvaal, Madagascar, São Paulo in Brazil, Paisano Pass in West Texas, United States, and Montreal, Quebec, Canada.

The rock of Salem, Massachusetts, United States, is a mica-foyaite rich in albite and aegirine: it accompanies granite and essexite.

The lujaurites are distinguished from the rocks above described by their dark color, which is due to the abundance of minerals such as augite, aegirine, arfvedsonite and other kinds of amphibole.

Sodalite-syenites in which sodalite very largely or completely takes the place of nepheline occur in Greenland, where they contain also microcline-perthite, aegirine, arfvedsonite and eudialyte.

Urtite from Lujaur Urt on the White Sea consists very largely of nepheline, with aegirine and apatite, but no feldspar.

Jacupirangite (from Jacupiranga in Brazil) is a blackish rock composed of titaniferous augite, magnetite, ilmenite, perofskite and nepheline, with secondary biotite.

A worldwide average of the major elements in nepheline syenite tabulated by Barker (1983) is listed below, expressed as weight percent oxides.

This mixture is higher in alkali and aluminium and typically lower in iron and silica than feldspars from pegmatites making it a good raw material.