Palygorskite

• Attapulgite
• Attaclay
• Mountain leather
• Mountain cork
• Bergholz
• Mountain meat

The mineral palygorskite, outdated also known as mountain leather, mountain cork, mountain wood or mountain meats as well as attapulgite, is a sheet silicate with the chemical composition (Mg, Al) 4 [ OH | (Si, Al) 4O10 ] 2 · (4 4) H2O. The values ​​given in the parentheses of the elements magnesium and aluminum or silicon and aluminum can in the formula each represent each other (substitution, Diadochie ), but are always in the same proportions to the other components of the mineral.

It crystallizes in the monoclinic crystal system and is translucent to opaque, usually needle-like crystals, but also fibrous to massive aggregates of white, grayish to yellowish or gray-green color. In thin layers, it can also be colorless. Visible crystal faces and fibrous aggregates have a wax-like luster, massive aggregates, however, are rather earthy finish.

It may may be abundant in individual localities though, it is but overall not widespread.

Special Features

A part of its water of crystallization is firmly bound as water of constitution (including structural water ), another part against " zeolitic " only stored loose. When heated to 220 ° C up to 15% thereof may be gradually released.

Etymology and history

Was first discovered palygorskite in the so -called " Second Mine" on the river Popovka at Palygorsk in the Urals in Russia's Perm region. Was first described in 1862 by mineral TV Savchenkov, who named it after its type locality.

His other synonyms attapulgite got the minerals by an archaeological site near the town of Attapulgus in Georgia, USA.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the palygorskite belonged to the mineral class of " silicates and Germanates " and then to the Department of " layer silicates ( phyllosilicates ) ," where he, along with Falcondoite, Kalifersit, Loughlinit, sepiolite Tuperssuatsiait and Yofortierit the unnamed group VIII/H.33 formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the palygorskite also included in the category of " silicates and Germanates " and there in the department of " layer silicates ( phyllosilicates ) ". This division, however, is further divided according to the structure of the silicate layers, so that the mineral " Simple tetrahedral nets of six- rings, connected by octahedral nets or bands " can be found according to its construction in the subdivision where it only together with Tuperssuatsiait and forms Yofortierit the unnamed group 9.EE.20.

The mainly common in English-speaking classification of minerals according to Dana assigns the palygorskite in the class of " silicates and Germanates " and there in the department of " layer silicates: modulated mentals". Here he is the only member / along with Kalifersit, Tuperssuatsiait and Yofortierit in the " palygorskite Sepiolithgruppe ( palygorskite subgroup ) " with the system no. Find: " modulated layers with connected strip layer silicates " 74.03.01a within the subdivision.

Education and Locations

Palygorskite is formed hydrothermally in various rocks such as granite, marble or serpentinite.

Worldwide, so far (as of 2012) 265 localities for palygorskite known. Apart from its type locality " Second Mine" at Palygorsk the mineral still occurred in the past also in the Urals mine Sachara, the Tscheremschanskoje Mine and the deposits Sinar and Akkermanovskoe in Russia. Furthermore, the mineral is also found in the Republic of Sakha ( Yakutia ), in Kawalerowo, on the Kola Peninsula and in the Volga region.

In Germany the mineral previously could only be found in Marktredwitz (brick house), at several locations in Wunsiedel and on Zeilberg in Bavaria.

In Austria, palygorskite found so far, especially in Carinthia, Salzburg and Styria ( Friesach - hut mountain, Frauenkogel, Gail Valley Alps, Hohe Tauern, Koralpe, Oberdorf an der Laming ), but also in Atzelsdorf ( Brunn an der Wild ) in Lower Austria and Mauthausen in Upper Austria.

In Switzerland, palygorskite appeared on the Aare (Bern), Entlebuch LU ( Lucerne), Ennetburgen and Stansstad ( Nidwalden ), Crissier ( Vaud) in the Binn Valley (Valais) among others Buren.

Other localities lie including Australia, Bulgaria, Chile, China, Ecuador, France, Greenland, Iran, Iraq, Italy, Japan, Kazakhstan, Qatar, Kyrgyzstan, Madagascar, Mexico, Morocco, Namibia, Norway, Peru, Poland, Romania, Saudi Arabia, Sweden, Senegal, Slovakia, Slovenia, Spain, Czech Republic, Turkey, Ukraine, Uzbekistan, the United Kingdom and the United States.

Crystal structure

Palygorskite crystallizes in the monoclinic space group C2 / m ( Raumgruppen-Nr. 12) with the lattice parameters a = 12.70 Å; b = 17.83 Å; c = 5.24 Å and 95.8 ° β = and two formula units per unit cell.

Uses

If palygorskite on the surface, he is a reliable Paläoklimaanzeiger because it is converted to smectite rapidly under humid to semi-humid conditions.

For local enrichment palygorskite is used as thermal or sound insulation material use.

Palygorskite is due to its - sold as a jewelry stone imitation under the trade name Angel Skin Opal (see also gemstone ) - the opal -like appearance.

Researchers discovered on the bottom of a well in Chichen Itza, which the Maya used for human sacrifices to their rain god Chaac, a four meter thick layer of blue color. Only chemists were clarified by experiments that the " Maya Blue" pigment called using palygorskite and indigo, which are heated together, can be generated.