Langbeinite
Langbeinite is a rarely occurring mineral from the mineral class of " sulfates (including selenates, tellurates, chromates, molybdates and tungstates ) ". It crystallizes in the cubic crystal system with the idealized composition K2Mg2 [ SO4 ] 3, is so chemically seen a potassium -magnesium sulfate.
Langbeinite is rarely well developed, cubical or octahedral crystals. He usually finds himself nieriger in shape, bulbous or grained to massive mineral aggregates. In its pure form langbeinite is colorless and transparent. But it can also appear white and by foreign admixtures a yellowish pink to take red, green or gray color, the transparency decreases accordingly. Through multiple refraction due to lattice defects or polycrystalline training
Special Features
In water, langbeinite dissolves only slowly. It is milky white through faint glow.
Langbeinite is piezoelectric, meaning it builds similar to quartz by interval- like elastic deformations electrical voltage. In addition, he is also tribolumineszent, ie reacts with strong mechanical stress or friction with "cold light emission ".
Etymology and history
Langbeinite was first discovered in potash William Hall Anderbeck in Saxony- Anhalt and 1891 described by S. Zuckschwerdt, who named the mineral after Kommerzienrat Adalbert Langbein from Leopold Hall to honor his contributions to the development of Kalisalzindustrie in the region.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the langbeinite belonged to the Department of " water clear Sulfate [ SO4 ], without other anions ", where he was named the " Langbeinitgruppe " with the system no. Formed VI/A.03 and the other members Efremovit and Manganolangbeinit.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the langbeinite also in the department of " sulfates ( selenates, etc. ) without additional anions, without H2O" one. However, this is further divided according to the relative size of the cations involved, so that the mineral is found according to its composition in the subsection "With medium -sized and large cations " where it also together with Efremovit and Manganolangbeinit as a name the " Langbeinitgruppe " with System no. 7.AC.10 forms.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the langbeinite in the class of " sulfates, chromates and molybdates (including selenates, tellurates, Selenite. Tellurite and sulphites ) " and then in the Department of " sulfates " one. Here it is to find "with different formulas Anhydrous acids and sulfates " as a name in the " langbeinite series" 28/04/04 within the subdivision.
Education and Locations
Langbeinite forms, as well as other potassium salts, usually by evaporation and can thus be found mainly in marine salt domes, where it occurs associated among other things with carnallite, halite and sylvite. Langbeinite, however, can also result from the metamorphosis of sylvite, Kieserit or polyhalite.
A rare mineral formation langbeinite could be detected only in a few localities, where so far (as of 2013) are considered to be known about 35 localities. Apart from its type locality potash William Hall Anderbeck the mineral in Saxony -Anhalt entered even in the potash plant Solvayhall at Bernburg and the pit Berlepsch evident in Staßfurt. Other known localities in Germany include Giesel ( Neuhof ) and the Werra Valley in Hesse, Lower Saxony and Hänigsen and Wath in Ronneburg, flag and Unterbreizbach in Thuringia.
In Austria they found langbeinite among others in the salt mine Altausee in Styria, in the Hall Taler salt factory in Tyrol and in the salt works Perneck and Hallstatt in Upper Austria.
Other known localities include China, France, Pakistan, Poland, Tajikistan, Czech Republic, Russia and New Mexico in the United States.
Crystal structure
Langbeinite crystallized cubic space group P213 ( Raumgruppen-Nr. 198 ) with the lattice parameters a = 9.92 Å and four formula units per unit cell.
The crystal structure of langbeinite consists of a skeleton of [ SO4 ] 2 tetrahedra and Mg 2 ions in octahedral coordination with respect to the O2 - ions. In the cavities of this stand, the K ions are embedded.