Quartzite

Quartzite: A granoblastic metamorphic rock consisting mainly of quartz (>90%) and formed by recrystallization of sandstone or chert by either regional or thermal metamorphism. Accessory minerals include feldspar, micas, and detrital heavy minerals such as titanite, magnetite, zircon and rutile. The name is from German "Quarzit".

Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide (Fe₂O₃). Other colors, such as yellow, green, blue, and orange, are due to other impurities. The term quartzite is often misused to describe quartz arenite, in particular when these have experienced significant compaction and diagenetic overgrowth cementation. It can be difficult to distinguish the effects of diagenesis and metamorphism since these are essentially a continuum of the same process. Quartzite as a metasediment is often found interbedded with other metamorphic rocks with sedimentary protoliths such as slate, phyllite, schist, calc-silicate rocks, and marbles.

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Pure grey-white quartzite from Telemark, Norway. From Sand Atlas.

Relict sedimentary bedding in a quartzite, Telemark, Norway. From Sand Atlas.

Red quartzite (with hematite impurities). From Sand Atlas.

Yellow quartzite. From James St. John.

Green quartzite with fuchsite (chromian muscovite mica). Laramie Range, Wyoming, USA. From James St. John.

Bibliography

• Bucher, K., & Grapes, R. (2011). Petrogenesis of metamorphic rocks. Springer Science & Business Media.
• Fossen, H. (2016). Structural geology. Cambridge University Press.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Passchier, Cees W., Trouw, Rudolph A. J: Microtectonics (2005).
• Philpotts, A., & Ague, J. (2009). Principles of igneous and metamorphic petrology. Cambridge University Press.
• 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.
• Vernon, R. H. (2018). A practical guide to rock microstructure. Cambridge university press.

Photo
Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)
Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Quartz crystals in a quartzite. XPL image, 2x (Field of view = 7mm)
Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)
Garnet and muscovite crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. XPL image, 2x (Field of view = 7mm)
Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. XPL image, 2x (Field of view = 7mm)	Garnet and muscovite crystals in a quartzite. PPL image, 2x (Field of view = 7mm)
Garnet and muscovite crystals in a quartzite. PPL image, 20x (Field of view = 1mm)	Garnet, pink piemontite and muscovite crystals in a quartzite. PPL image, 20x (Field of view = 1mm)	Garnet, pink piemontite and muscovite crystals in a quartzite. PPL image, 20x (Field of view = 1mm)
Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)	Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)	Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)
Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)	Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)	Quarzite rich in muscovite. XPL image, 10x (Field of view = 2mm)