Natrolite

Natrolite is a commonly occurring mineral from the mineral class of " silicates and Germanates ", more specifically, a framework silicate of the zeolite group. It crystallizes in the orthorhombic crystal system with the chemical composition Na2 [ Al2Si3O10 ] • 2H2O and developed primarily long, prismatic to acicular or hair-like, radial- crystals, which are either colorless or white. Through foreign admixtures, the mineral can also take an orange - yellow or reddish color.

Natrolite is the sodium- rich end member of a continuous series of solid solutions, which is characterized by the exchange of calcium and water instead of sodium. The calcium- rich end member of the series (with the same crystal structure ) is Skolezit, Ca ( Al2Si3O10 ) • 3 H2O, while Mesolith intermediate composition ( Na2Ca2 ( Al6Si9O30 ) • 8 H2O).

Etymology and history

Was first found and described Natrolite from Hohentwiel in singing in 1803 by Martin Heinrich Klaproth. The name is a combination of two Greek words soda, and λίθος lithos for " stone ".

A 1887 by Traube described and designated as Laubanit mineral turned out, according to recent analysis by grape and Brendler and by Strunz as Natrolite out why the mineral name was discredited and attributed as the synonym natrolite.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Natrolith belonged to the mineral class of " silicates and Germanates " and then to the Department of " framework silicates ( tectosilicates ) " where he along with Gonnardite, Mesolith, Paranatrolith, Skolezit, Thomsonit (Ca ) and Thomsonit - ( Sr) formed a distinct subgroup, which belonged to the group of Faserzeolithe within the family of zeolites.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Natrolith 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 his name to the " Natrolithgruppe " with the System No.. Forms 9.GA.05 and the other members Gonnardite, Mesolith, Paranatrolith and Skolezit.

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

Education and Locations

Natrolite formed mainly by hydrothermal alteration feldspathic rocks. There Natrolite occurs as a major or minor component of the matrix or forms euhedral crystals in druses and fissures.

Locations are in addition to the type locality Hohentwiel and the emperor chair, among other Narssarssuk in Greenland, Teigarhorn in Iceland, Quebec in Canada, the Kola Peninsula in the Russian Federation, as well as Tálezly and Soutěsky in the Czech Republic.

Crystal structure

Natrolite crystallizes in the orthorhombic space group Fdd2 ( Raumgruppen-Nr. 43) with the lattice parameters a = 18.29 Å; b = 18.64 Å and c = 6.59 Å, and eight formula units per unit cell.