Syenite is an intrusive rock, belonging to the alkali series of intermediate plutonic rocks. Alkali feldspar (e.g. orthoclase) is the major mineral component of syenite, total feldspar content is > 65%, and quartz is typically lacking. It is found in continental settings, and typically results from partial melting of the lower crust. Syenite is the plutonic equivalent of trachyte.


Other specimens - Click the thumbnails to enlarge

Group - plutonic.
Colour - variable but typically light coloured.
Texture - phaneritic (medium to coarse grained).
Mineral content - orthoclase, with lesser to minor plagioclase, minor mica, augite, hornblende, magnetite etc.
Silica (SiO 2) content - 60%-65%.
Uses - dimension stone for building facings, foyers etc (often preferred to granite due to its better fire-resistant qualities); can be used as aggregate in the building and roading industries.
New Zealand occurrences - Inland Kaikoura Range, Dunedin Volcano.