Sanidine
Sanidine is a commonly 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) 4O8 ]. The values given in the parentheses elements potassium, sodium and silicon and aluminum can in the formula each represent each other (substitution, Diadochie ), but are always in the same proportions to the other components of the mineral.
Sanidine usually develops tabular or acicular to prismatic crystals and twins of up to 50 centimeters in size, but also spherical or granular to massive aggregates. Unweathered crystal faces have a glass-like luster, cleavage surfaces shimmer on the other hand rather nacreous.
In its pure form sanidine is colorless and transparent. But it may also appear white and accept by foreign admixtures a gray, yellowish or reddish color by multiple refraction due to lattice defects or polycrystalline training, the transparency decreases accordingly.
Etymology and history
The mineral name sanidine is a neologism that is σανις from the Greek terms [ medics ] for board, plank or board and εἶδος [ EIDOS ] composed for appearance or shape. It refers to the common embodiment of the plate-like crystals.
Was first described in 1789 by Karl Wilhelm sanidine Nose in his contributions "On the slate mountains etc. and Westphalen ", which were taken up in 1808 by Johann Jacob Noeggerath " Mineralogical studies on the mountains in the Lower Rhine " in his. As a type locality of the Drachenfels applies in the Rhenish Seven Mountains.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the sanidine belonged to the department of " framework silicates ( tectosilicates ), with zeolites ", where he along with Buddingtonit, celsian, Hyalophane, Kokchetavit, microcline, orthoclase, Paracelsian, Rubiklin and slawsonite the subgroup of " alkali feldspars " with the system no. VIII/J.06 formed within the group of the feldspars.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the sanidine contrast, in the department of " framework silicates ( tectosilicates ) without zeolitic H2O" one. This is also further divided according to the possible presence of other anions, so that the mineral is found according to its composition in the subsection " framework silicates ( tectosilicates ) without additional anions ", where it together with adularia, anorthoclase, Buddingtonit, celsian, Hyalophane, Kokchetavit, microcline, Monalbit, orthoclase and Rubiklin the reduced " feldspar group " with the system no. 9.FA.30 forms.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the sanidine likewise in the class of " silicates and Germanates " there, however in the department of " framework silicates: Al- Si lattice " field. Here he is with anorthoclase, celsian, Filatovit, Hyalophane, orthoclase, microcline and Rubiklin in the group of "K (Na, Ba) - feldspars " with the system no. 76.01.01 found within the subdivision "With Al- Si lattice ".
Modifications and varieties
Sanidine is a high- temperature modification of Alkalifeldspats with a largely disordered distribution of aluminum and silicon. Together with the high-temperature albite, it forms a complete mixed batch.
Education and Locations
Sanidine is a typical rock forming mineral and is formed in acidic volcanic rocks. In addition, it forms pseudomorphs after microcline. Accompanying minerals occur among others quartz, plagioclase, muscovite, biotite, hornblende and magnetite.
Worldwide, so far (as of 2012) about 480 localities known as. Apart from its type locality Drachenfels the mineral could be found at other locations in the Seven Mountains as among others at Finkenberg at Bonn, on the Mount of Olives, in Hardt and beads on Weilberg near King Winter and in the High Castle and Dächelsberg near Wachtberglifte. Furthermore, sanidine yet joined, among others, in several places in Baden- Württemberg ( Behind Hauenstein, Katzenbuckel, Oberbergen ), Bavaria ( Fichtelgebirge), in many places in the Eifel ( Andernach, down, Ettringen, Hille Home, Mendig, Niederzissen) in Rhineland -Palatinate in some places in the Saxon Erzgebirge, near Gera in Thuringia.
In Austria, sanidine found among others at Pauliberg near Kobersdorf in Burgenland; Goss village, Kloch and on Stradner Kogel and on Kate Reck near Bad Ischl in Styria.
Other localities lie among others in Algeria, Angola, Antarctica, Argentina, Armenia, Azerbaijan, Ethiopia, Australia, Bolivia, Brazil, Bulgaria, China, El Salvador, Eritrea, Estonia, France and belonging to France Caribbean island of Martinique, Greece, Guinea, Honduras, India, Italy, Japan, 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, Turkey, Hungary, the United Kingdom ( UK) and the United States of America (USA).
Crystal structure
Sanidine crystallizes in the monoclinic space group C2 / m ( Raumgruppen-Nr. 12) with the lattice parameters a = 8.6 Å; b = 13.03 Å; c = 7.18 Å and 116.0 ° and β = 4 formula units per unit cell.
Use
Sanidine has no economic significance in general. However, it is occasionally slurred with good quality of some experienced collectors to gemstones.