Ikaite
Ikaite | ||
---|---|---|
Specific gravity 1.83 | | |
Optical properties | Biaxial (−)[3] | |
Refractive index | nα = 1.455 nβ = 1.538 nγ = 1.545[4] | |
Birefringence | d = 0.090 | |
Other characteristics | Decomposes into water and calcite above 8 °C[3] | |
References | [2] |
Ikaite is the mineral name for the hexahydrate of calcium carbonate, CaCO3·6H2O. Ikaite tends to form very steep or spiky pyramidal crystals, often radially arranged, of varied sizes from thumbnail size aggregates to gigantic salient spurs. It is only found in a metastable state and decomposes rapidly by losing most of its water content once removed from near-freezing water. This "melting mineral" is more commonly known through its pseudomorphs.
Distribution
It is usually considered a rare mineral, but this is likely due to difficulty in preserving samples. It was first discovered in nature by the Danish
Structure
Ikaite crystallizes in the
Stability
Synthetic ikaite was discovered in the nineteenth century in a study by Pelouze.
Pseudomorphs
The presence of ikaite may be recorded through geological time through the presence of pseudomorphs of other calcium carbonate phases after it.[21] Although it can be hard to uniquely define the original mineral for every specimen, there appears to be good evidence for ikaite as the precursor for the majority of the following locality names of pseudomorphs:
- Glendonite, after type locality, Glendon, New South Wales, Australia.
- Thinolite, (Gr. Thinos = shore) found in the tufa of Mono Lake, California, US[22][23]
- Jarrowite, Jarrow, Northumberland, UK[24][25]
- Fundylite, Bay of Fundy, Nova Scotia, Canada
- Gersternkorner, (Ger. = Barleycorn)
- Gennoishi, (Jp. = hammerstones)[26]
- Molekryds, (Dan. = Mole Cross), Mors Island, Jutland, Denmark
- Pseudogaylussite (from semblance to Gaylussite)
- White Sea hornlets, White Sea and Kola peninsula.
Ikaite or its
The common ingredient appears to be cold temperatures, although the presence of traces of other chemicals such as nucleation inhibitors for anhydrous calcium carbonate may also be required. It has also been reported as forming in winter on Hokkaido at a saline spring.
Since cold water can be found at depth in the oceans even in the tropics, ikaite can form at all latitudes. However, the presence of ikaite pseudomorphs can be used as a
Thinolite deposits
Thinolite is an unusual form of calcium carbonate found on the shore (Greek: thinos = shore) of Mono Lake, California. This and other lakes now largely in the desert or semi-desert environments of the southwestern US were part of a larger post-glacial lake that covered much of the region near the end of the last glaciation. It is thought that at this time, conditions similar to that of the Ikka fjord allowed for the growth of massive ikaite.
Isotope geochemistry
Isotope geochemistry can reveal information about the origin of the elements that make up minerals. The isotopic composition of ikaite and the pseudomorphs is actively studied.[31] Studies of the ratio of 13C to 12C in ikaite relative to a natural, standard ratio can help to determine the origin of the carbon pool (organic/inorganic) which was consumed to form ikaite.[32] Some studies have shown that oxidizing methane is the source of both modern day ikaite and glendonites in high-latitude marine sediments. Similarly the ratio of 18O to 16O, which varies in nature with temperature and latitude, can be used to show that glendonites were formed in waters very close to the freezing point, in agreement with the observed formation of ikaite.
References
- S2CID 235729616.
- ^ a b Mineralienatlas.
- ^ a b Ikaite. Webmineral.
- ^ Ikaite. Mindat.
- doi:10.14430/arctic3545. Archived from the original(PDF) on 2014-05-25. Retrieved 2013-02-26.
- S2CID 129290259.
- .
- S2CID 4396798.)
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: CS1 maint: multiple names: authors list (link - ^ doi:10.1306/042800710176.)
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: CS1 maint: multiple names: authors list (link - S2CID 27836966.)
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: CS1 maint: multiple names: authors list (link - doi:10.1016/S0025-3227(03)00354-2.)
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: CS1 maint: multiple names: authors list (link - S2CID 14010315.)
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: CS1 maint: multiple names: authors list (link - doi:10.1016/0016-7037(93)90339-X.)
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: CS1 maint: multiple names: authors list (link - ^ Ekaterina Bazarova, Alexander Kononov and Oksana Gutareva (2016). Cryogenic Mineral Formations in the Okhotnichya Cave in the primorsky Mountain Ridge (Western Baikal Region, Russia), Eurospeleo Magazine 3: 47–59.
- ^ .
- doi:10.1524/zkri.1983.163.3-4.227.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ S2CID 101756996.
- ^ Pelouze, M.J. (1865). "Sur une combinaison nouvelle d'eau et de carbonate de chaux". C. R. Acad. Sci. 60: 429–431.
- S2CID 140724494.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - .
- ^ Kaplan, M.E. (1979). "Calcite pseudomorphs (pseudogaylusite, jarrowite, thinolite, glendonite, gennoishi) in sedimentary rocks. The origin of pseudomorphs (in Russian)". Lithology and Mineral Resources. 5: 125–141.
- .
- ^ a b E.S. Dana (1884). "A crystallographic study of the thinolite of Lake Lahontan". U.S. Geological Survey Bulletin (12): 429–450.
- ^ Browell, E. J. J. (1860). "Description and analysis of an undescribed mineral from Jarrow Slake". Tyneside Naturalists Field Club. V: 103–104.
- .
- .
- .
- ^ Kennedy,G.L.; Hopkins, D.M.; Pickthorn, W.J. (1987). "Ikaite, the glendonite precursor, in estuarine sediments at Barrow, Arctic Alaska". Annual Meeting Abstract Program. 9. Geological Society of America: 725.
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(help) - S2CID 101559852.
- .
- S2CID 130488236.
- S2CID 128872028.)
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: CS1 maint: multiple names: authors list (link
Further reading
- Jansen J. H. F., Woensdregt C. F., Kooistra M. J., van de Gaast S. J. (1987). "Ikaite pseudomorphs in the Zaire deep-sea fan: An intermediate between calcite and porous calcite". Geology. 15 (3): 245–248. doi:10.1130/0091-7613(1987)15<245:IPITZD>2.0.CO;2.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - Johnston J. D. (1995). "Pseudomorphs after ikaite in a glaciomarine sequence in the Dalradian of Donegal, Ireland". Scottish Journal of Geology. 31 (1): 3–9. S2CID 129695941.
- King, C., (1878). U. S. Geological exploration of the fortieth parallel, Vol. 1. Washington: D.C., U. S. Government Printing Office.
- Russell, I. C. (1889). Quaternary history of Mono Valley, California. Reprint from the Eighth Annual Report of the United States Geological Survey, Pages 267–394. Artemisia Press, Lee Vining, California 1984
External links
- Mineralogical and crystallographic data about ikaite
- Mineralogical and crystallographic data about ikaite Archived 2006-10-09 at the Wayback Machine
- Ikaite homepage
- Natural occurrences of ikaite
- Glendonites and pseudomorphs after ikaite (in German)
- Giant pseudomorphs after ikaite found on Moler Island, Jutland, Denmark
- Pyramidia – Lair of the Rare and Fascinating Glendonite
- A study of the type locality of the mineral ikaite