Natrolite
| Natrolite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Na 2 [Al 2 Si 3 O 10 ] • 2H 2 O |
|
Mineral class (and possibly department) |
Framework silicates (tectosilicates) - zeolite group - fiber zeolites |
|
System no. to Strunz and to Dana |
9.GA.05 ( 8th edition : VIII / J.21) 77.01.05.01 |
| Similar minerals | Mesolite , Skolezite |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-pyramidal; mm 2 |
| Space group | Fdd 2 (No. 43) |
| Lattice parameters | a = 18.29 Å ; b = 18.64 Å; c = 6.59 Å |
| Formula units | Z = 8 |
| Physical Properties | |
| Mohs hardness | 5 to 5.5 |
| Density (g / cm 3 ) | measured: 2.20 to 2.26; calculated: 2.25 |
| Cleavage | completely after {110}, clearly after {010} |
| Break ; Tenacity | shell-like |
| colour | colorless, white, gray, bluish, yellowish, pink |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, silk gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.473 to 1.483 n β = 1.476 to 1.486 n γ = 1.485 to 1.496 |
| Birefringence | δ = 0.012 to 0.013 |
| Optical character | biaxial positive |
| Axis angle | 2V = 58 ° to 64 ° (measured), 48 ° to 62 ° (calculated) |
| Other properties | |
| Chemical behavior | melts before the soldering tube |
| Special features | pyroelectric, piezoelectric, fluorescence |
Natrolith is a common mineral of the zeolite group within the mineral class of " silicates and germanates " with the chemical composition Na 2 [Al 2 Si 3 O 10 ] · 2H 2 O. It is thus seen a chemically hydrous sodium - aluminosilicate . Structurally, natrolite belongs to the tectonic silicates .
Natrolite crystallizes in the orthorhombic crystal system and develops predominantly long prismatic to needle-like or hair-shaped crystals , which are often connected to radial mineral aggregates . In its pure form, natrolite is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or polycrystalline formation, it can also appear white, with the transparency decreasing accordingly. Occasionally the mineral also takes on a gray, bluish, yellowish or pink color due to foreign admixtures .
Natrolite is the sodium-rich end link of a continuous series of mixed crystals , 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 scolecite , Ca (Al 2 Si 3 O 10 ) 3H 2 O, while mesolite is of intermediate composition (Na 2 Ca 2 (Al 6 Si 9 O 30 ) 8 H 2 O ).
Etymology and history
Natrolith vom Hohentwiel near Singen in Baden-Württemberg was first found and described in 1803 by Martin Heinrich Klaproth . The name is a combination of the Greek words Natron and λίθος lithos for "stone".
A mineral described by Hermann Traube in 1887 and called Laubanite turned out to be natrolite according to more recent analyzes by Traube and Brendler and Strunz , which is why the mineral name was discredited and assigned as a synonym for natrolite.
classification
In the outdated but still partially in use 8th edition of the mineral classification by Strunz of Natrolith belonged to the mineral class of "silicates and Germanates" and then to the Department of " framework silicates (tectosilicates)" where he collaborated with Gonnardite , Mesolith , Paranatrolith , Skolezit , Thomsonite- (Ca) and Thomsonite- (Sr) the subgroup "Fiber zeolites I" with the system no. VIII / J.21 within the zeolite family .
The valid since 2001 and by the International Mineralogical Association used (IMA) 9th edition of Strunz'schen systematic mineral other hand, assigns the Natrolith into the already finely subdivided department of the " framework silicates (tectosilicates) with zeolitic H 2 O; Family of zeolites ”. This is also further subdivided according to the crystal structure, so that the mineral, according to its structure, can be found in the sub-section "Zeolites with chains of four rings, connected via a fifth Si", where it is named after the "Natrolith group" with the system No. 9.GA.05 and the other members gonnardite, mesolite, paranatrolite and scolezite .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns natrolite to the class of "silicates and germanates" and there in the department of "structural silicates: zeolite group". Here he is also the namesake of the group " Natrolith and related species " with the system no. 77.01.05 and the other members Tetranatrolith , Paranatrolith, Mesolith, Skolezit, Edingtonit , Gonnardite, Cowlesit , Thomsonit-Ca, Sr and Thomsonit- Nabesit found within the subdivision of the "real zeolites".
Crystal structure
Natrolite crystallizes orthorhombically in the space group Fdd 2 (space group no. 43) with the lattice parameters a = 18.29 Å ; b = 18.64 Å and c = 6.59 Å and 8 formula units per unit cell .
Education and Locations
Natrolite is mainly formed by hydrothermal alteration of rocks containing feldspar . There natrolite occurs as a main or secondary component of the basic mass or forms idiomorphic crystals in drusen and fissures .
In addition to the type locality at Hohentwiel and the Kaiserstuhl , the sites include Narssarssuk in Greenland , Teigarhorn in Iceland , Québec in Canada , the Kola Peninsula in the Russian Federation and Tálezly and Soutěsky in the Czech Republic .
See also
literature
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th fully revised and updated edition. Springer Verlag, Berlin et al. 2005, ISBN 3-540-23812-3 , pp. 126 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Dörfler Verlag GmbH, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 272 .
Web links
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 701 .
- ↑ Webmineral - natrolites
- ↑ a b c d Natrolite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 79.1 kB )
- ↑ a b c d e Mindat - Natrolite
- ^ MH Klaproth (1803): Chemical investigation of natrolite . Gesellschaft Naturforschender Freunde zu Berlin, Neue Schriften Vol. 4, pages 243–248
- ^ New mineral names. Discredited Minerals. Laubanite (= Natrolite) In: American Mineralogist No. 11–12, November – December 1957, p. 919 ( PDF 191.7 kB ; English, p. 3)