Sanidine
| Sanidine | |
|---|---|
 |
|
| General and classification | |
| chemical formula | (K, Na) [(Si, Al) 4 O 8 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates - framework silicates |
|
System no. to Strunz and to Dana |
9.FA.30 ( 8th edition : VIII / J.06) 76.01.01.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | C 2 / m (No. 12) |
| Lattice parameters |
a = 8.6 Å ; b = 13.03 Å; c = 7.18 Å β = 116.0 ° |
| Formula units | Z = 4 |
| Twinning | Carlsbad twins, more rarely Baveno and Manebach twins |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | measured: 2.56 to 2.62; calculated: [2.56] |
| Cleavage | completely after {001}, clearly after {010}; Secretions after {100} |
| Break ; Tenacity | uneven to shell-like; brittle |
| colour | colorless, white, gray, yellowish, reddish |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass luster, mother-of-pearl luster on split surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.518 to 1.525 n β = 1.523 to 1.530 n γ = 1.525 to 1.531 |
| Birefringence | δ = 0.007 |
| Optical character | biaxial negative |
| Axis angle | 2V = 60 ° (measured); 48 to 64 ° (calculated) |
| Pleochroism | colorless |
Sanidin is a frequently occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the chemical composition (K, Na) [(Si, Al) 4 O 8 ]. The elements potassium and sodium as well as silicon and aluminum indicated in the round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral.
Sanidin mostly develops tabular or needle-like to prismatic crystals and twins up to 50 centimeters in size, but also spherical or granular to massive aggregates . Unweathered crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer.
In its pure form, sanidin 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. Sanidin can also take on a gray, yellowish or reddish color through foreign admixtures.
Etymology and history
The mineral name Sanidin is a word created from the Greek terms σανίς sanís for "board, plank, table" and εἶδος eídos for "appearance, shape". He refers to the common tabular form of crystals.
Sanidin was first described in 1789 by Karl Wilhelm Nose in his articles "Ueber das Schiefergebirge etc. and about Westphalen", which were taken up in 1808 by Johann Jacob Nöggerath in his "Mineralogical Studies on the Mountains on the Lower Rhine". The Drachenfels in the Rhenish Siebengebirge is considered a type locality .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Sanidin to the department belonged " framework silicates (tectosilicates), with zeolites ", where he together with Buddingtonit , celsian , Hyalophane , Kokchetavit , microcline , orthoclase , Paracelsian , rubicline and Slawsonite, the subgroup of "alkali feldspars" with system no. VIII / J.06 within the group of feldspars .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies sanidine in the category of “tectosilicates without zeolitic H 2 O”. This is further subdivided according to the possible presence of further anions , so that the mineral can be found in the sub-section “Tectosilicates without additional anions” according to its composition, where it can be found together with adulara , anorthoclase , buddingtonite, celsian, hyalophane, kokchetavite , Mikroklin, Monalbit , Orthoclase and Rubiklin the reduced "feldspar group" with the system no. 9.FA.30 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns Sanidin to the class of "silicates and Germanates", but there it is in the category of "structural silicates: Al-Si lattice". Here he is together with Anorthoklas, Celsian, Filatovit , Hyalophan, Orthoklas, Mikroklin and Rubiklin in the group of "K (Na, Ba) -Feldspars" with the system no. 76.01.01 to be found in the subsection " With Al-Si grid ".
Modifications and varieties
Sanidine is a high-temperature modification of alkali feldspar with a largely disordered distribution of aluminum and silicon . Together with the high-temperature albite , it forms a complete mixed series .
Education and Locations
Sanidin is a typical rock-forming mineral and forms in acidic volcanic rocks . In addition, it forms pseudomorphoses according to Mikroklin . As Begleitminerale occur among others quartz , plagioclase , muscovite , biotite , hornblende and magnetite on.
So far (as of 2012) around 480 sites are known worldwide. In addition to its type locality in Drachenfels, the mineral could also be found in other places in the Siebengebirge such as on the Finkenberg near Bonn, on the Ölberg , near Perlenhardt and on the Weilberg near Königswinter as well as near Hohenburg and on the Dächelsberg in Wachtberg . Furthermore, Sanidin appeared in several places in Baden-Württemberg (Hinterhauenstein, Katzenbuckel, Oberbergen), Bavaria (Fichtelgebirge), in many places in the Eifel (Andernach, Daun, Ettringen, Hillesheim, Mendig, Niederzissen) in Rhineland-Palatinate , in some places in the Saxon Ore Mountains and near Gera in Thuringia.
In Austria, Sanidin was found on the Pauliberg near Kobersdorf in Burgenland, near Gossendorf , Klöch and on the Stradner Kogel as well as on the Katereck near Bad Ischl in Styria.
In Switzerland, Sanidin has so far only been found near Oberbargen (Schaffhausen) and on Monte San Giorgio (Ticino).
Other sites are found in Algeria, Angola, Antarctica, Argentina, Armenia, Azerbaijan, Ethiopia, Australia, Bolivia, Brazil, Bulgaria, China, El Salvador, Eritrea, Estonia, France and on the Caribbean island of Martinique, Greece, which belongs to France, Guinea, Honduras, India, Italy, Japan, Canada, Kenya, Korea, Lesotho, Madagascar, Mexico, Mongolia, Myanmar, Namibia, New Zealand, Nicaragua, Paraguay, Poland, Portugal, Romania, Russia, Sweden, Slovakia, Spain, Sri Lanka, South Africa, Taiwan, Tanzania, the Czech Republic, Turkey, Hungary, the United Kingdom (Great Britain) and the United States of America (USA).
Crystal structure
Sanidine crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a = 8.6 Å ; b = 13.03 Å; c = 7.18 Å and β = 116.0 ° and 4 formula units per unit cell .
use
Sanidin is generally of no economic importance. However, if it is of good quality, it is occasionally ground into gemstones by some experienced collectors .
See also
literature
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 263 ( Dörfler Natur ).
Web links
- Mineral Atlas: Sanidin (Wiki)
- Webmineral - Sanidine (English)
- Uni-Tübingen: Mineral adhesions - paramorphoses, or transformation pseudomorphoses using the example of Sanidin-Mikroklin
- Geology info - feldspar
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 694 .
- ↑ a b c d e Sanidine , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 76.3 kB )
- ↑ a b c d Mindat - Sanidine
- ↑ Johann Jakob Nöggerath: Sanidin , in: Mineralogical studies on the mountains on the Lower Rhine , Verlag Johann Christian Hermann, Frankfurt 1808, pp. 24–39 ( PDF 416.5 kB )
- ↑ Martin Okrusch, Siegfried Matthes: Mineralogie . 7th edition. Springer Verlag, Berlin 2005, ISBN 3-540-23812-3
- ↑ Mindat - Locations for Sanidin
- ^ Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich a. a. 2002, ISBN 3-405-16332-3 , pp. 220 .