Scolecite

• Kalkmesotyp

Skolezit, outdated also known as Kalkmesotyp, is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the composition Ca [ Al2Si3O10 ] · 3H2O, is thus a calcium aluminum silicate, which is one and belongs to the group of Faserzeolithe due to its crystal structure to the framework silicates.

Skolezit is transparent to translucent and develops predominantly long, prismatic to acicular crystals in radialstrahligen mineral aggregates. Also fibrous, globular and massive aggregates as well as contact and penetration twins are known. Larger, intact crystal faces have a glass-like shine, on the other hand feinndadelige aggregates tend to show a silky sheen.

Skolezit is the calcium rich end member of an uninterrupted series of solid solutions, which is characterized by the exchange of calcium and water instead of sodium. The sodium- rich end member of the series (with the same crystal structure ) is Natrolite while Mesolith is of intermediate composition.

Special Features

Skolezit is pyroelectric and piezoelectric, ie builds on intermittently taking place temperature and deformation on an electrical charge. Under UV light, show some Skolezite a yellow to brown fluorescence.

Etymology and history

The name of the mineral refers to the worm-like curving Skolezit when heated before the blowpipe (Greek scolex, hookworm).

Skolezit was first described in 1813 by the German scholar Adolph Ferdinand Gehlen and Johann Nepomuk Fuchs. Whether the material examined by them as suspects later, actually comes from the Berufjörðurgebiet in Iceland (which is commonly regarded as the type locality), but is not guaranteed.

Originally by René -Just Haiiy 1801 mesotype term coined (from the Greek μέσος for middle and τύπος for shape) ( Kalkmesotyp ) was to the 20th century for what is now known as Natrolithgruppe and summarized minerals natrolite ( Natronmesotyp ) Mesolith and Skolezit used.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz of the mineral class of " silicates and Germanates " belonged and there to the Department of " framework silicates ( tectosilicates ) " where he along with Gonnardite, Mesolith, Natrolite, Paranatrolith, Thomsonit - (Ca) and Thomsonit - ( Sr), the " zeolite group: subgroup Faserzeolithe " with the system no. VIII/J.21 formed.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Skolezit 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 department is also further divided according to the crystal structure, so that the mineral is found in accordance with its construction in the subsection " zeolites associated with four - ring chains over a fifth Si ", where it together with Gonnardite, Mesolith, Natrolite and Paranatrolith the " Natrolithgruppe "with the system number. 9.GA.05 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Skolezit in the class of " silicates and Germanates " and there in the department of " framework silicates: Zeolite - group " field. Here he is with Natrolite, Tetranatrolith, Paranatrolith, Mesolith, edingtonite, Gonnardite, Cowlesit, Thomsonit (Ca ), Thomsonit - ( Sr) and Nabesit in the group " Natrolite and related species " with the system no. Find 77.01.05 within the sub-division of "real zeolites ".

Education and Locations

As the related minerals Mesolith and Natrolite is Skolezit a decomposition product of basalt and comes together with other zeolites and Apophyllite as hydrothermal formation of drusen in front. Also, in some igneous and metamorphic rocks occurs Skolezit than divide mineral. Skolezit produced during low-grade metamorphism in the Zeolithfazies. Accompanying minerals occur in addition to the Apophyllite and other zeolites already defined, you still calcite, prehnite and stilbite.

As a rather rare mineral formation Skolezit can indeed be abundant in part to different sites, overall it is not very common. So far (as of 2012) are considered to be known around 300 localities.

Known due to exceptional Skolezitfunde among other Nashik, but also other places in the Indian state of Maharashtra, where up to 20 cm large crystals were found. In the 1960s was due to a tunnel, which is also known as " The Antas - tunnel", discovered a large Zeolithvorkommen in the Brazilian state of Rio Grande do Sul near Veranópolis. Next 20 cm and 25 cm Apophylliten Natroliten Skolezite there were also up to 20 cm long and 1 cm to light.

In Germany, only a few sites have been previously known, among other things, the quarry at Höwenegg (Baden- Württemberg), the Zeilberg (Bavaria), Roßdorf and Ortenberg (Hesse), St. Andrew Berg ( Lower Saxony), Remblinghausen (North Rhine- Westphalia), Arensberg and Lautzenbrücken ( Rhineland -Palatinate ), Baerenstein (Saxony) and the basalt quarry " patch -pit " near Eisenach ( Thuringia).

In Austria, the mineral occurred mainly in Carinthia and Salzburg in the area of the Hohe Tauern, but also in Styria and Tyrol Skolezite were found.

In Switzerland, Skolezit found among others at Aargrat in the canton of Bern, in several places in the cantons of Graubünden and Valais and in some places in the cantons of Ticino and Uri.

Other localities lie among others in the Antarctic, Argentina, Australia, Brazil, Bulgaria, Chile, China, Costa Rica, Denmark, Eritrea, France, Iceland, Israel, Italy, Japan, Canada, Madagascar, Namibia, New Zealand, Nicaragua, Norway, Poland, Reunion, Romania, Russia, Sweden, Slovakia, Spain, South Africa, Taiwan, Tanzania, Czech Republic, Ukraine, Hungary, the United Kingdom ( UK) and the United States of America (USA).

Crystal structure

Skolezit crystallizes in the monoclinic space group Cc ( Raumgruppen-Nr. 9) with the lattice parameters a = 18.51 Å; b = 18.97 Å; c = 6.53 Å and 90.6 ° β = and 8 formula units per unit cell.

Use

Skolezit is offered rarely and mainly for collectors as a precious stone in faceted or cut mugeliger form.