Nepheline
| Nepheline | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | (Na, K) [AlSiO 4 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.FA.05 ( 8th edition : VIII / J.02) 76.02.01.02 |
| Similar minerals | Kalsilite , Kaliophilite |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | hexagonal-pyramidal; 6th |
| Space group | P 6 3 (No. 173) |
| Lattice parameters | a = 9.99 Å ; c = 8.38 Å |
| Formula units | Z = 8 |
| Frequent crystal faces | {0001} |
| Twinning | pseudo- holohedral |
| Physical Properties | |
| Mohs hardness | 5.5 to 6 |
| Density (g / cm 3 ) | measured: 2.55 to 2.66; calculated: [2.64] |
| Cleavage | no |
| Break ; Tenacity | uneven to scalloped |
| colour | colorless, white, gray, green, yellow, brown |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss to fat gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.529 to 1.546 n ε = 1.526 to 1.542 |
| Birefringence | δ = 0.003 to 0.004 |
| Optical character | uniaxial negative |
| Other properties | |
| Special features | breaks down like clouds into hydrochloric acid |
Nepheline (also Eläolith or Fettstein ) is a frequently occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the hexagonal crystal system with the chemical composition (Na, K) [AlSiO 4 ] in different colors from white and gray to green, red and yellow to brown. Nepheline can also be colorless.
The mineral belongs to the group of foids , which means that it is related to the alkali feldspars , but poor in silicon dioxide (SiO 2 ).
Etymology and history
Nepheline was found for the first time at the 1801 Monte Somma described by Italy and René Just Haüy , of the mineral after the Greek word νεφέλη Nephele to form precipitating silica clouds for "cloud" named because of its property in the decomposition in strong acids.
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of nepheline belonged to the mineral class of "silicates and Germanates" and then to the Department of " framework silicates (tectosilicates)" where he collaborated with Kaliophilit the "nepheline Kaliophilit Group “With the system no. VIII / J.02 and the other members Kalsilit , Megakalsilit , Malinkoit , Panunzit , Trikalsilit and Yoshiokait formed.
The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns nepheline to the class of “silicates and germanates” and there to the “tectosilicates” section without zeolitic H 2 O “a. However, this section is further subdivided according to the possible presence of further anions , so that the mineral can be found according to its composition in the sub-section of "tectosilicates (tectosilicates) without additional anions", where it is named after the "nepheling group" with the system no . 9.FA.05 and the other members form Kaliophilit, Kalsilit, Megakalsilit, Panunzit, Trikalsilit and Yoshiokait.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns nepheline to the class of "silicates", but there in the department of "structural silicates with Al-Si lattice". Here he is also the namesake of the "Nepheling group" with the system no. 76.02.01 to be found in the sub-section " Framework silicates: Al-Si lattices, feldspar representatives and related species ".
Crystal structure
Nepheline crystallizes hexagonally in the space group P 6 3 (space group no. 173) with the lattice parameters a = 9.99 Å and c = 8.38 Å as well as 8 formula units per unit cell .
properties
Nepheline is difficult to distinguish from quartz , but in contrast to this, it decomposes in strong acids such as hydrochloric acid , whereby the resulting silica precipitates like clouds.
Education and Locations
Nepheline forms igneously in alkaline rocks such as syenite and pegmatite , less often in basalt or gneiss . Together with leucite and the like, it is an important rock-forming mineral.
As a rather rare mineral formation, nepheline can sometimes be abundant at various locations, but overall it is not very common. So far, more than 600 sites are known worldwide (as of 2011). In addition to its type locality Monte Somma, the mineral was also found in Italy on Vesuvius and Roccamonfina ( Province of Caserta ) in Campania, in the Grotta del Cervo ( Province of L'Aquila ) in Abruzzo, in several places in Lazio , near Lesina in Apulia, on Monte Ferru found in Sardinia, Linosa (Sicily) and near San Venanzo in Umbria.
In Germany, nepheline was found in the Black Forest , Hegau and Odenwald in Baden-Württemberg, in Franconia and the Upper Palatinate in Bavaria, near Fulda and Hofgeismar in Hesse, near Güntersen am Backenberg in Lower Saxony, in many places in the Eifel in Rhineland-Palatinate, near Löbau in Saxony, near Eckernförde and Kiel in Schleswig-Holstein as well as near Meiningen and in the Thuringian Forest in Thuringia.
In Austria, Nephelin appeared on Pauliberg in Burgenland as well as in Bad Gleichenberg , Klöch and Mühldorf near Feldbach in Styria. So far, only Ramsen SH and Centovalli are known at Swiss sites .
Worth mentioning because of the extraordinary finds of nepheline is Davis Hill near Bancroft (Ontario) in Canada, where crystals of up to 70 cm in length have been discovered. Although only 3.5 cm long, but fully developed crystals are known from Mont Saint-Hilaire in the Canadian province of Québec.
Other sites are Afghanistan , Angola , several sites in East Antarctica , Argentina , Armenia , Azerbaijan , Australia , Bolivia , Brazil , Chile , China , Democratic Republic of the Congo ( Zaire ), Ecuador , Finland , France , Greenland , Guatemala , Guinea , India , Japan , Cameroon , Canada , Kazakhstan , Kenya , Kyrgyzstan , Colombia , Korea , Libya , Madagascar , Malawi , Mali , Morocco , Mexico , Mongolia , Myanmar ( Burma ), Namibia , New Zealand , Norway , Paraguay , Peru , Poland , Portugal , Romania , Russia , Sweden , Slovakia , Somaliland , Spain , South Africa , Tajikistan , Tanzania , Czech Republic , Uganda , Ukraine , Hungary , Uzbekistan , the United Kingdom , the United States of America (USA) and the Central African Republic .
Nepheline was also found in rock samples from the East Pacific Ridge .
use
Nepheline is of little importance as an aluminum ore, but was used as such in the former Soviet Union, as it did not have any significant deposits of the bauxite otherwise used for this purpose .
In the glass and ceramic industry , nepheline is used as an additive and filler for certain polymers. For the latter, it is important that nepheline and certain polymers ( e.g. polyvinyl chloride ) have almost the same refractive index , so that the transparency of the polymer is retained even with a high filler content.
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 767 (first edition: 1891).
Web links
Individual evidence
- ↑ Webmineral - Nepheline (English)
- ↑ a b c d 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. 691 .
- ↑ Nepheline . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 73 kB ]).
- ↑ a b c Mindat - Nepheline (English)
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (= Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 261 .
- ↑ a b List of sites for nepheline in the Mineralienatlas and Mindat
- ↑ Walter Pohl, Wilhelm Petrascheck (Greetings): W. & WE Petrascheck's deposit theory . 4th edition. Schweizerbart, Stuttgart 1992, ISBN 3-510-65150-2 , p. 203, 285-286 .
- ^ Refractory ceramics to silicon carbide . In: Wolfgang Gerhartz (Ed.): Ullmann's Encyclopedia of Industrial Chemistry . 5th edition. Volume A 23. VCH, Weinheim 1993, ISBN 978-3-527-20123-5 , pp. 682-685 .