Kyanite
A blue aluminosilicate mineral with strongly anisotropic hardness.
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Its name derives from the Greek word kyanos, meaning deep blue.[1] Disthene and cyanite are alternative names for kyanite.[2]
Key facts and history
Andalusite and sillimanite have a polymorph that is stable only at high pressure: kyanite.[2] Metamorphic rocks containing kyanite generally signal that metamorphism took place deep within the Earth's crust.[2] Biotite gneiss, mica schist, and hornfels that formed under high pressure during regional metamorphism are common hosts for kyanite.[3] Granite, pegmatites, and associated quartz veins occasionally contain kyanite as well.[3]
To define a metamorphic zone that experienced great depth in the crust, kyanite is frequently employed as an index mineral.[4] In his foundational study of metamorphic rocks in Scotland, G. M. Barrow delineated zones based on the presence of kyanite.[4] When heated above 1100 °C, kyanite breaks down into mullite and vitreous silica.[5]
What the research sources say
The Geology Page account states kyanite in metamorphic rocks generally indicates pressures higher than four kilobars.[1] A BBC Science article quotes Prof Stewart saying kyanite only forms at very deep depths and under extensive pressure.[6] That article adds that elsewhere the ancient continent has been eroded away, the ground cannot support such skyscrapers.[6]
References
- "Geology Page - Kyanite", Geology Page, 2014-05-16. facts only, no text reused. geologypage.com
- Wikipedia, "Kyanite" (CC BY-SA 4.0), which cites: "Glossary of geology.", American Geological Institute, 1997 (we also read that source) en.wikipedia.org
- Wikipedia, "Kyanite" (CC BY-SA 4.0), which cites: Nesse 2000, p. 315; "Geology Page - Kyanite", Geology Page, 2014-05-16; Sinkankas, "Mineralogy for amateurs.", Van Nostrand, 1964, p. 529 (we also read that source) en.wikipedia.org
- Wikipedia, "Kyanite" (CC BY-SA 4.0), which cites: Yardley, "An introduction to metamorphic petrology", Longman Scientific & Technical, 1989, p. 8–10 (we also read that source) en.wikipedia.org
- Wikipedia, "Kyanite" (CC BY-SA 4.0), which cites: Speyer, "Thermal Analysis of Materials", CRC Press, 1993, p. 166; Nesse 2000, p. 315 (original not read by us) en.wikipedia.org
- Quinn, "How ancient collision shaped New York skyline", BBC Science, 6 June 2013. facts only, no text reused. bbc.co.uk
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Kyanite (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Kyanite (CC BY-SA 4.0).
- Word definitions: the , each quoted from its Wikipedia article.
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