Ijolite
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Ijolite is an igneous rock consisting essentially of nepheline and augite.[1] Ijolite is a rare rock type of considerable importance from a mineralogical and petrological standpoint. The word is derived from the first syllable of the Finnish words such as Iivaara, Iijoki · and Ii, all geographical names in Finland, and the Ancient Greek Xiflos, a stone. Ijolite occurs in various parts of the Kainuu region of eastern Finland and in the Kola Peninsula of northwest Russia on the shores of the White Sea.[2] Ijolite was first defined and named by Finnish geologist Wilhelm Ramsay.[3]
The pyroxene is morphic[clarify], yellow or green, and is surrounded by formless areas of nepheline. The accessory minerals are apatite, cancrinite, calcite, titanite and schorlomite, a dark-brown titaniferous variety of melanite-garnet. This rock is the plutonic and holo-crystalline analogue of the nephelinites -volcanic equivalent and nepheline-dolerites; it bears the same relation to them as the nepheline syenites have to the phonolites.[2]
A leucite-augite rock, resembling ijolite except in containing leucite in place of nepheline, is known to occur at Shonkin Creek, near Fort Benton, Montana, and was earlier called missourite,[2] but is now regarded as a variety of leucitite.[4]
References
[edit]- ^ Kresten, Peter; Troll, Valentin R. (2018). "The Alnö Carbonatite Complex, Central Sweden". GeoGuide. doi:10.1007/978-3-319-90224-1. ISBN 978-3-319-90223-4. ISSN 2364-6497. S2CID 135266142.
- ^ a b c Chisholm 1911.
- ^ Lindberg, Johan (January 19, 2011). "Ramsay, Wilhelm". Uppslagsverket Finland (in Swedish). Retrieved November 30, 2017.
- ^ Gupta, A.K and Yagi, K. (1980). Petrology and Genesis of Leucite-Bearing Rocks. Berlin: Springer-Verlag. ISBN 978-3-642-67552-2.
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- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Ijolite". Encyclopædia Britannica. Vol. 14 (11th ed.). Cambridge University Press. p. 298.
