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.


syenite

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 (SiO2) 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.