Leucite
| Leucite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | K [AlSi 2 O 6 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates - framework silicates |
|
System no. to Strunz and to Dana |
9.GB.05 ( 8th edition : VIII / J.05) 76.02.02.01 |
| Similar minerals | Nepheline , sanidine |
| Crystallographic Data | |
| Crystal system | High leucite: cubic (> 605 ° C) deep leucite: tetragonal (<605 ° C) |
| Crystal class ; symbol | High leucite: cubic hexakisoctahedral; 4 / m 3 2 / m deep leucite: tetragonal-dipyramidal; 4 / m |
| Space group | see crystal structure |
| Lattice parameters | see crystal structure |
| Formula units | Z = 16 |
| Frequent crystal faces | {112}, {100}, {110} |
| Twinning | mostly after {110} and {101} |
| Physical Properties | |
| Mohs hardness | 5.5 to 6 |
| Density (g / cm 3 ) | measured: 2.45 to 2.50; calculated: [2.46] |
| Cleavage | very indistinct after {110} |
| Break ; Tenacity | uneven to shell-like; brittle |
| colour | colorless, gray, white, yellowish, reddish |
| Line color | White |
| transparency | transparent to opaque |
| shine | Glass gloss |
| radioactivity | hardly detectable |
| Crystal optics | |
| Refractive indices |
n ω = 1.508 n ε = 1.509 |
| Birefringence | δ = 0.001 |
| Optical character | uniaxial positive |
| Axis angle | 2V = very low |
| Other properties | |
| Chemical behavior | sensitive to hydrochloric acid and oxalic acid |
Leucite , sometimes also spelled leucite or referred to as leukolite , potash-alumina-silicate or also white garnet , is a rather seldom occurring mineral from the mineral class of " silicates and germanates " with the chemical composition K [AlSi 2 O 6 ]. Structurally it belongs to the framework silicates and there to the family of zeolites .
Leucite is dimorphic , which means that it occurs in different crystalline forms (modifications) with the same chemical composition. Naturally formed leucite first crystallizes at over 900 ° C in the cubic crystal system ( high leucite ) and then changes to the tetragonal crystal system ( deep leucite ) at a temperature between 600 and 700 ° C. Depending on the source, a transition temperature of 605 ° C or 630 ° C is also mentioned.
Leucite mainly develops clearly recognizable icositetrahedra - crystals (formerly: leucitoeder ), but also occurs in the form of granular to massive mineral aggregates . In its pure form it is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation or polysynthetic twinning , it can also appear white and, due to foreign admixtures, take on a gray or yellowish to reddish color, the transparency decreasing accordingly. Unweathered and clear crystal surfaces have a glass-like sheen , crevice or fracture surfaces also have a greasy sheen . Most leucite crystals, however, are matt white due to the formation of twin lamellae when they are converted to deep leucite.
Etymology and history
Leucite was first discovered on Monte Somma in the Italian metropolitan city of Naples and described in 1791 by Abraham Gottlob Werner , who named the mineral after the ancient Greek word λευκός leukós "white" due to its frequently occurring white color .
When Martin Heinrich Klaproth analyzed the leucite in 1797, he discovered for the first time in a mineral potash, previously known exclusively as a product of the plant kingdom (also known as “plant alkali”) in the form of potash .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the leucite belonged to the division of "tectosilicates (tectosilicates), with zeolites", where together with ammonioleucite it forms the "leucite group" with the system no. VIII / J.05 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns leucite to the category of “tectosilicates with zeolitic H 2 O; Family of zeolites ”. This is, however, further subdivided according to the framework structure, so that the mineral can be found according to its structure in the sub-section “Chains of simply connected rings of four”, where together with ammonioleucite, analcime , Hsianghualite , lithosite , pollucite and wairakite it forms the “analcime group “With the system no. 9.GB.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns leucite to the class of "silicates and germanates" and there in the department of "structural silicates: Al-Si lattice". Here it is also together with ammonioleucite in the "leucite group" with the system no. 76.02.02 can be found in the sub-section " Framework silicates: Al-Si lattices, feldspar representatives and related species ".
Crystal structure
Deep leucite crystallizes tetragonally with the space group I 4 1 / a (space group no. 88) with the lattice parameters a = 13.05 Å and c = 13.75 Å and 16 formula units per unit cell .
High leucite crystallizes cubically in the space group Ia 3 d (no. 230) with the lattice parameter a = 13.43 Å and 16 formula units per unit cell.
properties
Leucite alone is also infusible on charcoal in front of the soldering tube. Together with borax, however, it slowly dissolves, forming a clear pearl of light brown color.
Leucite is dissolved by hydrochloric acid and hydrofluoric acid , whereby the resulting silica precipitates in the form of a powder in hydrochloric acid.
Under the microscope, leucite often shows idiomorphic octagonal outlines, but sometimes only rounded shapes. Due to the low refraction of light of the leucite, these can look like holes in a thin section. Typical of leucite is the appearance of oriented inclusions (smaller crystals, glass) along former outer crystal surfaces (so-called "cinder rings"). Crossed polarization filters often show weakly birefringent twin lamellae, which can be arranged differently in different fields of a crystal.
Education and Locations
Leucite is a typical igneous high-temperature mineral and is formed when lavas that are rich in alkali and poor in SiO 2 solidify . It is known as leucite phonolite , leucitophyr and leucite basalt . There it occurs in paragenesis together with analcime , augite , biotite , kalsilite , labradorite , microcline , montmorillonite , natrolite , nepheline , olivine and orthoclase . In addition, there are also pseudomorphoses from Orthoclase to Leucite. Since, like nepheline , it is low in SiO 2 , it is never found next to quartz , as this is a sign of SiO 2 excess in the rock.
As a rather rare mineral formation, leucite can sometimes be abundant at different sites, but overall it is not very common. So far (as of 2013) around 190 sites are known to be known. In addition to its type locality Monte Somma, the mineral occurred in Italy in several places in the municipality of Roccamonfina , on Vesuvius and on the island of Procida in Campania; in the Grotta del Cervo near Carsoli in Abruzzo; on Monte Vulture in Basilicata; at Paola in Calabria; in many places in the provinces of Rome and Viterbo in Latium; on Etna in Sicily; at Pitigliano in Tuscany and at Spoleto , San Venanzo and Orvieto in Umbria.
In Germany the mineral could be found at Maleck , on the Titisee and on the Eichberg near Oberrotweil in Baden-Württemberg; can be found on the Zinster Kuppe near Kemnath and on the Zeilberg in Bavaria. In Hesse, leucite occurs on the slag heaps of the Hessenhütte in the Richelsdorfer Mountains and in numerous places in the Vogelsberg : For example, in the nepheline indolerites of Meiches as xenomorphic, yellowish-white masses, next to it often as rock-forming, only microscopically or radiographically detectable mineral, for example at Watzenborn-Steinberg , in a basalt quarry near Gonterskirchen and Ettingshausen . Leucite could also be found in many places in the Rhineland-Palatinate Eifel such as in the vicinity of Andernach , Hillesheim , the Laacher See and Mendig .
In Austria, leucite is so far only known from the Stradner Kogel near Merkendorf- Wilhelmsdorf and from a basalt quarry near Klöch in Styria.
The only known site in Switzerland so far is Reiat in the canton of Schaffhausen.
Known due to extraordinary leucite finds are among others the Vesuvius in Italy and the Laacher See in Germany, where well-developed crystals with a diameter of several centimeters were found.
Other previously known sites are in Antarctica, Argentina, Azerbaijan, Australia, Brazil, Cape Verde, China, France and French Polynesia, Greenland, India, Japan, Cameroon, Canada, the Democratic Republic of the Congo, Madagascar, Namibia, Norway , Paraguay, Poland, Romania, Russia, Sweden, Slovakia, Spain, South Africa, South Korea, Tanzania, Czech Republic, Turkey, Hungary and the United States of America (USA).
use
As a raw material
Leucite rocks are used in some countries such as B. Italy as a raw material for the production of potassium and aluminum .
In dentistry , leucite is used as a basic material for the production of ceramics for dentures such as inlays and partial crowns . It can be pressed in a special process and is therefore an alternative to zirconium oxide , which has to be milled.
As a gem
Occasionally, leucite is also processed into gemstones by collectors and hobby cutters , whereby it is mainly given a facet cut .
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. 770 (first edition: 1891).
- Helmut Schrätze , Karl-Ludwig Weiner : Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 859-860 .
- Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 123-124 .
- Dorian M. Hatch, Subrata Ghose, Harold T. Stokes: Phase transitions in leucite, KAlSi 2 O 6 . In: Physics and Chemistry of Minerals . tape 17 , 1990, pp. 220-227 , doi : 10.1007 / BF00201453 (English).
Web links
- Mineral Atlas: Leucite (Wiki)
- Leucite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on May 7, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Leucite. In: rruff.geo.arizona.edu. Retrieved May 7, 2019 .
- Michael RW Peters: Leucite. In: realgems.org. October 11, 2010, accessed on May 7, 2019 (with sample images of faceted Leucite).
Individual evidence
- ↑ a b c d e f g 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. 693 (English).
- ^ David Barthelmy: Leucite Mineral Data. In: webmineral.com. Retrieved May 7, 2019 .
- ↑ a b c Leucite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 63 kB ; accessed on May 7, 2019]).
- ↑ a b Leucite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 7, 2019 .
- ↑ a b c d Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 264 .
- ↑ a b c Martin Heinrich Klaproth : Chemical investigation of the leucite . In: Contributions to the chemical knowledge of mineral bodies . tape 2 , 1797, pp. 39–61 ( available online at rruff.info [PDF; 846 kB ; accessed on May 7, 2019]).
- ^ G. Diego Gatta, Nicola Rotiroti, Tiziana Boffa Ballaran, Alessandro Pavese: Leucite at high pressure: Elastic behavior, phase stability, and petrological implications . In: American Mineralogist . tape 93 , 2008, p. 1588–1596 (English, available online at rruff.info [PDF; 1.8 MB ; accessed on May 7, 2019]).
- ↑ a b c Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 607-608 .
- ^ Fiorenzo Mazzi, Ermanno Galli, Glauco Gottardi: The crystal structure of tetragonal leucite . In: American Mineralogist . 61 date = 1976, p. 108–115 (English, available online at rruff.info [PDF; 864 kB ; accessed on May 7, 2019]).
- ^ Walter Schumann: Collecting stones and minerals; find, prepare, determine . BLV Buchverlag GmbH & Co.KG, Munich et al. 1994, ISBN 3-405-14590-2 , p. 110 .
- ↑ Hans Pichler, Cornelia Schmitt-Riegraf: Rock -forming minerals in thin sections . 2nd Edition. Ferdinand Enke, Stuttgart 1993, ISBN 3-8274-1260-9 , pp. 44-45 .
- ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 860 .
- ↑ Localities for Leucite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 7, 2019 .
- ↑ Otto Diehl: About Nephelindolerite in Vogelsberg . In: Geologische Landesanstalt Hessen (Hrsg.): Notes of the Hessische Geologische Landesanstalt zu Darmstadt . tape V , no. 18 . Hessischer Staatsverlag, Darmstadt 1937, p. 168-176 .
- ^ Georg Greim: The minerals of the Grand Duchy of Hesse . Reprint 1 edition. Dieter W. Berger, Bad Vilbel 1994, ISBN 3-926854-04-9 , pp. 40 .
- ↑ Wilhelm Schottler : The basalts of the area around Gießen . In: Treatises of the Grossherzoglich Hessische Landesanstalt zu Darmstadt . tape IV , no. 3 . A. Bergsträßer, Darmstadt 1908, p. 371 .
- ↑ William Schottler : Notes on the Geological Map of Hesse, leaves Nidda and Scots . Hessischer Staatsverlag, Darmstadt 1924, p. 29-30 .
- ↑ William Schottler : Notes on the Geological Map of the Grand Duchy of Hesse, Leaf Laubach . Hessischer Staatsverlag, Darmstadt 1918, p. 41-42 .
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (= Dörfler Natur ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 271 .
- ↑ List of localities for Leucite in the Mineralienatlas and Mindat
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 220 .