Distinctive features:  
Texture and granularity and its composition.

Colour: 
White, pinkish-grey to grey.

Texture and granularity: 
Granular -- coarse to very coarsely grained.

Composition: 
Orthoclase more dominant than plagioclase (if plagioclase is dominant, the rock is probably diorite). Quartz is absent but there are small amounts of hornblende, mica, augite and magnetite, which are easily seen in coarse examples. Nepheline and leucite may also be present.

Field associations: 
Uncommon rocks that may be associated with nearby granites, but generally from magma chambers underlying trachytic (the fine-grained equivalent of syenite) volcanoes.

Varieties:
Syenite, which contains more orthoclase than plagioclase and no quartz; nepheline syenite, which is mostly plagioclase (labradorite).

 

Worldwide, but particularly in the Alps. Germany, Noraway, Azores, Africa, Russia, USA (New England, Arkansas, Montana and other states).

 

Building industry, superior to granite because of its fire-resisting qualities.