LARVIKITE
Larvikite is one of my favorite rocks. It's a
variety of monzonite, though it's sometimes misperceived as a variety of
syenite. Larvikite is dominated by large crystals of spectacularly
bluish-iridescent (schillerescent) perthitic feldspar (closely intergrown
potassium feldspar and plagioclase feldspar). The play of colors is the
result of light being dispersed along the plagioclase and K-feldspar crystal
boundaries. The smaller black crystals are pyroxene.
Varieties of larvikite are popular
decorative/ornamental stones known commercially as "Blue Pearl
Granite", "Emerald Pearl Granite", and other names. They
are quarried from the Larvik Batholith (aka Larvik Pluton, Larvik
Complex, Larvik Plutonic Complex), a suite of 10 igneous plutons emplaced in
the Oslo Rift (Oslo Graben) surrounded by ~1.1 billion year old Sveconorwegian
gneisses. The Larvik Batholith dates to about 292-298 million years old
(early Early Permian). Many quarries exploit larvikite in the vicinity of
the town of Larvik in southwestern Vestfold County, southern Norway.
Larvikite ("Blue Pearl Granite")
Larvikite ("Emerald Pearl Granite")