Glauconite

Glauconite is a very common mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the chemical composition (K, Na) ( Fe 3 , Al, Mg ) 2 [ (OH) 2 | (Si, Al) 4O10 ]. Structurally, glauconite to the layer silicates ( phyllosilicates ).

Glauconite developed almost exclusively platy or massive to earthy mineral aggregates of green color, which can also play yellowish or bluish.

Etymology and history

The mineral was named because of its color from the ancient Greek word γλαυκός [ Glaucus ] with the Homeric meaning " shiny ", "blue - green " or " blue - gray ". The original meaning of the word is derived probably from γλαῦξ [ Glaux ] or γλαύξ [ Glaux ], genitive γλαυκός [ Glaucus ] "Owl" from, and would thus " owl -like" hot. Used what extent the different meanings in Homer, is a point of contention of classical philology.

First described and named after his color glauconite in 1828 by the German mineralogist Christian Keferstein.

Classification

Already in the outdated, but partly still in use 8th edition of the mineral classification by Strunz was one of the glauconite to the Department of " layer silicates ( phyllosilicates ) ," where he along with Brammallit, illite and Wonesit the group of " alkali poor mica " with the System No.. VIII/H.13 formed within the mica group.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the glauconite also in the department of " layer silicates ( phyllosilicates ) " a. However, this is further subdivided according to the crystal structure, so that the mineral according to its construction in the subsection " layer silicates ( phyllosilicates ) with mica sheets, composed of tetrahedral and octahedral nets " can be found, where it, along with Aluminoseladonit, Boromuskovit, Chernykhit, Chromseladonit Chromphyllit, Ferriseladonit, Ferroaluminoseladonit, Ferroseladonit, Ganterit, Montdorit (Rd), muscovite, Nanpingit, paragonite, phengite ( mineral group ), roscoelite, celadonite, Tainiolith, Tobelit, Voloshinit the " Muskovitgruppe " with the system no. 9.EC.15 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the glauconite in the department of " layer silicate minerals " one. Here he is in the " mica group (muscovite - subgroup ) " with the system no. To find " layers of six-membered rings with 2:1 layers phyllosilicates " 71.02.02a within the subdivision.

Education and Locations

Glauconite is formed by conversion of detrital biotite, illite or other starting materials such as faecal pellets of soil organisms in marine diagenesis in shallow water under reducing conditions. Direct precipitation from sea water is rare. Preferred educational institutions are sandstones and clay (also form green earth) and limestone, often in the company of phosphorites.

As a rather rare mineral glauconite formation can indeed be abundant in part to different sites, overall it is not very common. So far (as of 2014) are considered to be known around 300 localities.

In Germany glauconite could, among other near Würzburg in Bavaria, in the limestone quarries near Rüdersdorf in Brandenburg, the Pit " Emilie " in Peine in Lower Saxony, in the Neanderthal limestone quarry and in different quarries in the Sauerland region in North Rhine- Westphalia and in Barmstedt, Lübeck- Moisling - Niendorf and Great Pampau be found in Schleswig -Holstein.

In Austria, found the mineral, among others, in the quarry of the cement works Wietersdort in the municipality Klein Sankt Paul and at Fox oven at Dobra mountain ( Kappel am Krappfeld ) in Carinthia, at Ernst Brunn in Lower Austria, at several locations in Salzburg, in a quarry near Vils in Tirol as well as in Weinzierl Bruck ( Grieskirchen ), St. Georgen an der Gusen and Plesching (district Urfahr ) in Upper Austria.

In Switzerland, you know glauconite so far only from a limestone quarry at Mellikon in the canton of Aargau and from Ängisort near Seedorf UR in the canton of Uri.

Other localities lie among other things in Egypt, Antarctica, Australia, Belgium, Bolivia, China, Denmark, France, Georgia, Israel, Italy, Japan, Canada, Malta, Morocco, New Zealand, the Netherlands, Poland, Russia, Sweden, Slovakia, South Africa, Tunisia, Ukraine, Hungary, England in the United Kingdom as well as in many states in the United States.

Even in rock samples from the upper continental slope off the coast of New Jersey ( USA) and from Sadorücken off the coast of the Japanese island of Honshu glauconite could be detected.

Crystal structure

Glauconite crystallizes in the monoclinic space group C2 / m ( Raumgruppen-Nr. 12) with the lattice parameters a = 5.246 Å; b = 9.076 Å; c = 10.184 Å and β = 101.1 ° and two formula units per unit cell.