Okenite

Okenit is a rarely occurring mineral from the mineral class of silicates and Germanates. It crystallizes in the triclinic crystal system with the chemical composition Ca 10 [ Si6O16 | ( Si6O15 ) 2] · 18 H 2 O, then, is a hydrous calcium silicate layer.

Okenit developed mainly leaf - to needle-shaped crystals in radialstrahligen, spherical mineral aggregates of white to pale yellow color.

Special Features

Before the blowpipe to Okenit puffs and melts into a white glass.

Etymology and history

Okenit was discovered together with many other minerals by Major Petersen, of the samples at " Kudlisat on Waygat " on Disko Island ( Kalaallisut: Qeqertarsuaq ) gathered up in Greenland and the academic collection in Munich handed, where the Okenit initially kept as a variety of Faserzeolith been. Through detailed analysis of the material, however, Franz von Hess Peter introduced in 1828 found that there had to be a distinct mineral species, which he described in his lecture on the mineral in the Assembly of German Natural Scientists in Berlin in September 1828 in honor of the naturalist and founder of the Assembly of German naturalists and Physicians Lorenz Oken as Okenit.

In the published shortly after the meeting archive recordings of Karl Wilhelm Gottlob Kastner, however, there is first the mineral name Ockenit. This is corrected only in the Addendum to Okenit because it turns out to be spelling errors in the handwritten records of KOBELL, which was brought by mistake without correction in print.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Okenit belonged to the mineral class of " silicates and Germanates " and then to the Department of "transitional structures between chain and layer silicates ", where after the latest update it ( 2008) single member of the unnamed group forms VIII/G.01.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Okenit also in the class of " silicates and Germanates " there, however, directly in the department of " layer silicates ( phyllosilicates ) " a. This department is also further divided according to the crystal structure, so that the mineral according to its composition in the subdivision of "simple tetrahedral grids with 4, 5, (6) and 8 rings involved " is to find where it is the only member of the unnamed group 9 forms. EA.40.

The mainly common in English-speaking classification of minerals according to Dana assigns the Okenit in the class of " silicates and Germanates " there, however, in the already fine divided department of the " layer silicates: Two-dimensional infinite layers with other than six -membered rings " one. Here he is with tobermorite Klinotobermorit, Plombierit, Riversideite, Tacharanit, Nekoit and Oyelith in the " tobermorite (5 - and 8- membered rings ) " with the system no. 72.03.02 within the sub-division of " layer silicates: Two-dimensional infinite layers with other than six -membered rings: 3 -, or 5- membered rings and 8- membered rings - 4" to find.

Education and Locations

Okenit formed from hydrothermal fluids in basalt cavities. Accompanying minerals include various zeolites and Apophyllite and calcite, prehnite and quartz (eg as chalcedony ).

A rare mineral formation Okenit has so far (as of 2012) are detected only at a few localities, of which approximately 60 localities as have been established. In Greenland Okenit previously occurred only at its type locality on Disko Island.

Known for its rich Okenitfunde in the form of spherical aggregates in basalt cavities is mainly the area around Poona in India.

In Germany Okenit found among others at Teichel mountain and at the quarry Zeilberg in Bavaria and at the quarry Bramburg in Lower Saxony. The only known locality in Austria is on the Brucker expressway, near the tunnel Kirchdorf in Steiermarker community Pernegg an der Mur.

Other localities lie among other things in Antarctica, Australia, Azerbaijan, Chile, Costa Rica, Denmark, Iceland, Israel, Italy, Canada, Mexico, New Zealand, Norway, Romania, Russia, Ukraine, Hungary, the United Kingdom ( UK ) and the United States of America.

Crystal structure

Okenit crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 2) with the lattice parameters a = 9.69 Å; b = 7.28 Å; c = 22.02 Å; α = 92.7 °; β = 100.1 ° and γ = 110.9 ° and one formula unit per unit cell.