Micro-Monzonite

Monzonite is an igneous intrusive rock. It is composed of approximately equal amounts of plagioclase and alkali feldspar, with less than 5% quartz by weight. It may contain minor amounts of hornblende, biotite and other minerals. If quartz constitutes greater than 5%, the rock is termed a quartz monzonite. Latite or trachyandesite are the approximate volcanic equivalents of monzonite. Monzonite was originally named after the Monzoni range in Val di Fassa (Trento Province - Italy).
Monzonite is a relatively uncommon rock type. It usually does not form its own plutons. Monzonitic magma most likely forms only a part of a generally more acidic (granitic) intrusions. A great variety of names (now all obsolete) have been attributed in time to these rocks:

Windsorite: Obsolete name for a light-colored quartz-monzonite aplite with minor amount of Biotite. named by Daly in 1903 after Windsor, Vermont, USA
Ukrainite: A local name for Quartz-monzonite; from type locality in Ukraine
Masanite: A Quartz-monzonite containing phenocrysts of zoned plagiolcase and corroded quartz in a granophyric groundmass. Name given by Koto (1909) from Masan-po, Korea
Sörkedalite: A local name for a variety of Olivine monzodiorite consisting of abundant antiperthitic andesine, mantled by anorthoclase, and by olivine; minor amount of clino-pyroxene and biotite may be present. From Sorkedal, Oslo, Norway.
Larvikite: A variety of augite syenite or monzonite consisting of rhombshaped ternary feldspars (with a distinctive schiller), from Larvik, Oslo Igneous Province, Norway.
Vallevarite: An obsolete local name for a variety of anorthosite, consisting essentially of andesine and microcline antiperthite with minor diopside and biotite. From Vallevara, Sweden.
Amherstite: A leucocratic variety of quartz belonging to the charnockitic rock series. The rock consists essentially of andesine-microcline antiperthite with minor quartz and hypersthene. From Amherst County, Virginia,USA.
Kjelsaite: A local name given to a plagioclase-rich larvikite which is a variety of augite syenite or monzonite. From Kjelsas, Oslo district, Norway.

Monzonite sample (plagioclase white, Alkali feldspar pink and femic minerals).

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
Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)
Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 2x (Field of view = 7mm)
Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)	Plagioclase, Hornblende and interstitial Orthoclase. PPL image, 10x (Field of view = 2mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)
Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)
Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)	Plagioclase, Hornblende and interstitial Orthoclase. XPL image, 10x (Field of view = 2mm)