Kyanite
A blue aluminosilicate mineral indicating high-pressure metamorphism.
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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
Kyanite is strongly anisotropic, with a hardness of 5.5 parallel to {001} and 7 parallel to {100}.[3] Andalusite and sillimanite are polymorphs of kyanite, which is the high-pressure form.[2] Metamorphic rocks containing kyanite generally point to metamorphism occurring deep within the Earth's crust.[2] A steel needle can scratch kyanite along its long axis (hardness 5.5) but not perpendicular to it (hardness 7).[3]
Kyanite possesses a perfect {100} cleavage and a second good cleavage on {010} that intersects the first at 79 degrees.[4] High-pressure regional metamorphism of pelitic rocks produces biotite gneiss, mica schist, and hornfels, all of which can contain kyanite.[5] Granite, pegmatites, and associated quartz veins occasionally host kyanite as well.[5] When heated above 1100 °C, kyanite breaks down into mullite and vitreous silica.[6]
What the research sources say
The Geology Page account states that kyanite in metamorphic rocks generally indicates pressures higher than four kilobars.[1] A BBC Science article by Quinn quotes Prof Stewart saying, "Kyanite is a key mineral to identify, we know it only forms at very deep depths and under extensive pressure".[7] The same source states that kyanite is found in Manhattan schist, which formed under extreme pressure during the collision of landmasses that created Pangaea.[1]
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: "Kyanite", Handbook of Mineralogy, 2001; "Kyanite", MinDat; Sinkankas, "Mineralogy for amateurs.", Van Nostrand, 1964, p. 528–529 (original not read by us) en.wikipedia.org
- Wikipedia, "Kyanite" (CC BY-SA 4.0), which cites: Sinkankas, "Mineralogy for amateurs.", Van Nostrand, 1964, p. 528–529; Nesse, "Introduction to mineralogy", Oxford University Press, 2000, p. 319; Sinkankas, "Mineralogy for amateurs.", Van Nostrand, 1964, p. 528–529 (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: 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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