Ikaite

  • Hydrocalcit
  • IMA 1962-005

Ikaite is a very rarely occurring mineral from the mineral class of " carbonates and nitrates ." It crystallizes in the monoclinic crystal system with the composition Ca [ CO3 ] · ​​6H2O, that is chemically a hydrous calcium carbonate.

Since Ikaite only to about 8 ° C is chemically stable and also merges into calcite due to crystal water loss, are mainly found only pseudomorphs of calcite after Ikaite, also referred to as " Glendonit ". True Ikaitkristalle have a tabular habit and are usually only a few millimeters in size. However, are also known submarine, columnar mineral aggregates of several tens of centimeters in thickness and several meters in height with a porous bark of small, shiny Ikaitkristallen.

Special Features

Ikaite is chemically unstable and dehydratiert at about 8 ° C, that is, it loses its water of crystallization and becomes the mineral calcite.

Etymology and history

Was first discovered in Ikaite Ikkafjord (also Ikka Firth or Ika Fjord ), or more precisely near the local " Ikka Grønnedal complex" Ivittuut in Greenland and described in 1963 by the German mineralogist Hans Pauly, who named the mineral after its type locality.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Ikaite belonged to the mineral class of " carbonates, nitrates and borates " and then to the Department of " water -containing carbonates without foreign anions ", where he along with Barringtonit, Hellyerit, Lansfordit, monohydrocalcite and nesquehonite the " nesquehonite - Lansfordit group " with the system no. V/D.01 formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Ikaite in the new class of " carbonates and nitrates " (here, the borates form a separate class). There, the mineral is still one in the department of " Carbonates without additional anions, with H2O" one. However, this is further divided according to the relative size of the involved cations and the element group membership of the metals, so that the mineral is found according to its composition in the subsection "With large cations ( alkali and alkaline earth carbonates ) ", where it is the only member the unnamed group 5.CB.25 forms.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Ikaite as the outdated Strunz'sche systematics in the common class of " carbonates, nitrates and borates " and there in the department of " water -containing carbonates " one. Here he can be found as the only member of the unnamed group 15:01:04 within the subdivision " Hydrous carbonates with A ( XO3 ) · x (H2O) ".

Modifications and varieties

Glendonit is the most famous pseudomorphs of calcite after Ikaite. Similar pseudomorphs of calcite after Ikaite are also known under the name Fundylit, Jarrowit or Thinolith, the latter actually refers to a pseudomorphs of calcite after Gaylussite.

Education and Locations

Ikaite forms in sea water under anaerobic conditions in periglacial and glaziomariner environment, ie geological areas that were formed or influenced by frost and glaciers or, with rich in organic material.

As a very rare mineral formation Ikaite has so far been detected only in a few mineral samples and known as valid so far (as of 2013) less than 10 localities .. Its type locality Ikkafjord this is the only known locality in Greenland, where, however, with a length of 10 meters, the largest ever, columnar mineral aggregates were found.

Other localities include

  • The Hunter Valley in New South Wales, Australia, where up to 20 inches wide Glendonit - pseudomorphs were found.
  • The coda - cave near Beroun in the Czech Central Bohemian Region
  • Shiowakka in the sub-prefecture of Tokachi on the Japanese island of Hokkaidō
  • The flow Olenitsa, which flows near the Russian Kola Peninsula to the White Sea and is also known for his hedgehog - or star-shaped Glendonit - pseudomorphs.
  • Natron Mono Lake in the U.S. state of California.

An important discovery is considered the Ikaitfund in Antarctica, particularly in Adélie Land, the Bransfield Strait and Weddell Sea, with potentially great importance in the global carbon cycle. The mineral was discovered there in two Antarctic expeditions in 2006 and 2007 by a team of scientists led by Gerhard Dieckmann.

Crystal structure

Ikaite crystallizes in the monoclinic space group C2 / c ( Raumgruppen-Nr. 15) with the lattice parameters a = 8.79 Å; b = 8.31 Å; c = 11.02 Å and β = 110.5 °, and four formula units per unit cell.

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