Larvikite

Larvikite: A variety of augite syenite or monzonite consisting of rhomb-shaped ternary feldspar (containing all three-endmember components albite, anorthite and orthoclase), dark amphibole, Ti-augite and Fe-rich micas. Minor nepheline, Fe-rich olivine or quartz may be present. The name originates from the town of Larvik in Norway, where this type of igneous rock is found. The K-feldspar is typically microscopically inhomogeneous to form perthitic intergrowths of K-feldspar and acid plagioclase with a near-albite composition. This give the characteristic grey-blue luster (adularescence or Schiller’s effect) on polished surfaces.

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Larvikite: ternary feldspar (grey-blue) and dark femic minerals. Oslo graben, Norway. From Hildegard Wilske

Larvikite: ternary feldspar (grey-blue) and dark femic minerals. Oslo graben, Norway. From Hildegard Wilske

Larvikite: ternary feldspar (grey-blue) and dark femic minerals. Oslo graben, Norway. From Hildegard Wilske

Larvikite: ternary feldspar (grey-blue) and dark femic minerals. Oslo graben, Norway. From Hildegard Wilske

Bibliography

• Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., Bateman, P., & Lameyre, J. (2002). Igneous rocks. A classification and glossary of terms, 2. Cambridge University Press.
• Middlemost, E. A. (1986). Magmas and magmatic rocks: an introduction to igneous petrology.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.

Photo
Ternary feldspar crystals (colorless), augite (light brown) with red-biotite inclusions and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence) and magnetite (black). XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (colorless), augite (light brown), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (colorless), augite (light brown), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (colorless), augite (light brown, with apatite inclusions), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (colorless), augite (light brown, with apatite inclusions), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (colorless), augite (light brown, with apatite inclusions), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (colorless), augite (light brown, with apatite inclusions), biotite (red) and magnetite (black). PPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence), augite (high birefringence), biotite (red) and magnetite. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (grey birefringence) with biotite (red) and magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence) with biotite (red) and magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence) with biotite (red) and magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystals (grey birefringence) with magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence) with magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)	Ternary feldspar crystals (grey birefringence) with magnetite (dark) inclusions. XPL image , 2x (Field of view = 7mm)
Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 10x (Field of view = 2mm)	Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 10x (Field of view = 2mm)	Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 10x (Field of view = 2mm)
Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 20x (Field of view = 1mm)	Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 20x (Field of view = 1mm)	Ternary feldspar crystal (grey birefringence) with ilmenite-magnetite exsolutions (the elongate plates). XPL image , 20x (Field of view = 1mm)