Erionite

Erionite is a collective name for those of the International Mineralogical Association (IMA ) recognized minerals and end links of a complete mixed batch, consisting of erionite -Na, erionite -K and Ca - erionite. This rarely- occurring minerals belong to the family of zeolites within the mineral class of " silicates and Germanates " and crystallize in the hexagonal crystal system with the following chemical composition:

• Erionite - Na: Na10 [ Al10Si26O72 ] • 24.6 H2O
• Erionite -K: K10 [ Al10Si26O72 ] • 32H2O
• Erionite - Ca: Ca 5 [ Al10Si26O72 ] • 31H2O

Special Features

Erionite developed primarily radial- fibrous or wool-like mineral aggregates, but also rare prismatic crystals to about 15 mm in length with a hexagonal habit. Also adhesions Offretite and Levyn are known. In feinnadeliger, fibrous aggregate form erionite is white and translucent, occasionally yellowish discolored by foreign admixtures with silky luster. The crystals themselves are colorless, transparent and show their faces vitreous luster.

Even if the fine needle-like crystals and fibers look like wool and also feel so, they are nevertheless due to their brittleness very sensitive to mechanical stress. Even with a light touch, they can be quickly destroyed.

Etymology and history

Erionite was first discovered in rhyolite tuff at Durkee in Baker County in the U.S. state of Oregon and described in 1898 by Arthur Starr Eakle, the Greek ἔριον / Erion / for " wool" named the mineral because of its wool-like appearance usually after the Greek word.

In 1997, the "Commission on new minerals, mineral names and classification " decided (English: Commission on new Minerals, Nomenclature and Classification ) a redefinition and renaming of many minerals of the Zeolithfamilie, which also belongs erionite. After Douglas S. Coombs et al. is no longer recognized as a mixed number erionite but their end members erionite - Na ( described in 1969 by Sheppard and Gude ), erionite -K ( described in 1998 by Passaglia et al. ) and erionite - Ca ( described in 1967 by Harada et al. ). recognized as a distinct minerals.

Erionite has been known as a carcinogen (cancer- promoting substance ) that forms large, near surface deposits, especially in the vicinity of the Turkish village Tuzköy, but also in other regions of Cappadocia and finding there in the Tuffgesteinen used as building material. The cancer rate in these areas because of air pollution with fine mineral fibers on average ( sometimes up to 100-fold higher), so abandoned the villages and their residents are to be relocated.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the erionite belonged to the mineral class of " silicates and Germanates " and there to the general ward of the " framework silicates ( tectosilicates ) " where she along with Bellbergit, chabazite (Ca), chabazite (K ), chabazite (Na), chabazite ( Sr), gmelinite (Ca), gmelinite (K ), gmelinite (Na), Levyn (Ca ), Levyn (Na ), mazzite, mazzite (Na), offretite Perlialith, Tschernichit and Willhendersonit the " zeolite group (subgroup Würfelzeolithe ) " formed.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the erionite also in the class of " silicates and Germanates " there, however, in the already fine divided department of the " framework silicates ( tectosilicates ) with zeolitic H 2 O; Family of zeolites " one. This division, however, is further subdivided according to the crystal structure, so that the erionite is found according to their construction in the subdivision " Zeolites with chains of five rings ", only where they still form the unnamed group 9.GD.20 together with Bellbergit.

The classification of minerals according to Dana assigns the erionite in the class of " silicates and Germanates " there, however in the department of " framework silicates: Zeolite Group." Here they are along with chabazite - Ca, chabazite -Na, K - chabazite, chabazite -Sr, Herschelit, Willhendersonit, Offretite gmelinite Na, Ca gmelinite, gmelinite K, faujasite -Na, faujasite - Ca, Mg faujasite, Levyn - Ca, Na - Levyn and Tschortnerit in the group of " chabazites and related species " with the system no. Find 77.01.02 within the sub-division of "real zeolites ".

Education and Locations

Erionite form in volcanic as basalt or rhyolite - tuffs converted, but also by sedimentation of salt lakes fallen, volcanic ash. Accompanying minerals include calcite, dolomite, montmorillonite, opal, quartz, celadonite and various zeolites.

Worldwide could erionites generally so far (as of 2011) are detected at around 160 localities, including, inter alia in East Antarctica, Australia, Bulgaria, Denmark, Germany, France, Greece, Iceland, Italy, Japan, Canada, New Zealand, Austria, Poland, Russia, Spain, Switzerland, Turkey, the United Kingdom ( UK, United Kingdom ) and the United States of America (USA).

Specifically, as erionite -Na identified minerals were first (type locality) on Cady Mountain in the U.S. San Bernardino County be detected but also found himself on the mountain Nero Montecchio Maggiore (San Pietro) in Italy, on the Japanese island of Iki, at Dunseverick lying in the far north of the Northern Ireland County Antrim and also in the United States at Mount Killdeer in Dunn County ( North Dakota) and in the " Durkee Fire Opal Mine " in Baker County ( Oregon).

As erionite -K identified minerals of the U.S. states of Arizona, Oregon and Washington have been found mainly in Kamloops in Canada, Otago in New Zealand and in several regions, where Rome is registered in Marion County (Oregon ) as the type locality.

As erionite -Ca minerals were identified, among others, on Ettringer Bellerberg, a volcano in Ettringen ( Eifel) in Germany; at Yssingeaux in France; with Oristano in Sardinia and Monte Fasolo ( Euganean Hills ) and at Mount Nero Montecchio Maggiore in Italy; at Maze in the Japanese prefecture of Niigata; Usti nad Labem in the Czech Republic; at Tuzköy in Turkey and in the U.S. counties Dunn, Slope and Stark in North Dakota and in Tillamook County, Oregon.

Crystal structure

All minerals crystallize in the hexagonal space group ( Raumgruppen-Nr. 194) with the adjacent, only slightly differing lattice parameters, and each one formula unit per unit cell.