ALKALINE
FELDSPAR SYENITE
Type
: Intrusive igneous rock
Chemistry
: Intermediate felsic
Components
: Essentials ; perthitic potassic feldspar. Accessories : quartz,
plagioclase (albite), olivine, acmite-angite pyroxene, titanite,
allanite, pyrrhotite, magnetite, ilmenite. Accidentals :
anorthoclase, nepheline.
Appearance
; pale to dark gray in color , with bluish high lights;
hypidiomorphic coarse-grained granular texture; massive structure
with frequent fluidal areas.
Geotectonic
environments
; small masses, often laccoliths or sills, inside or at the edge of
blocks of syenite and monzonite. They are derived by local
differentiation without any clear tectonic significance
Occurrence
: most characteristic are those of southern Norway and central
Norway. Alkaline feldspar syenites are also present in many parts of
Greenland and Canada.
Uses
: highly decorative, used as building stone, especially as polised
slabs. Larvikite is commercially known as “pale Labrador’’
