Mirabilite
- Glauber's salt
Mirabilite, as a natural Glauber's salt ( in older literature also dignified Glauber's salt), is a rarely occurring mineral from the mineral class of sulfates ( and relatives ). It crystallizes in the monoclinic crystal system with the chemical composition Na2 [ SO4 ] · 10H2O, is so chemically seen a sodium sulfate decahydrate.
Mirabilite developed mostly short to long prismatic crystals up to about 10 cm in length, but also block, granular or massive mineral aggregates and crusty coatings. Fresh samples are initially colorless and transparent, the surfaces show vitreous luster. On dry air mirabilite dehydrates very quickly, that is, it loses its water of crystallization and drying out, which he starts transforms into thenardite and matt white. Through foreign admixtures mirabilite can also assume a yellowish white to greenish white color.
With a Mohs hardness of 1.5 to 2.5 mirabilite is one of the soft minerals that are similar to the reference mineral gypsum ( 2 ) can be scratched with a fingernail.
Special Features
Mirabilite is not only sensitive to dehydration, but also slightly water soluble and can resolve itself in its own water of crystallization. Even in high humidity, the crystals dissolve relatively quickly. Specimens should always be kept in completely dry and airtight containers.
On the tongue mirabilite feels cool to the touch at first, but then tastes salty to bitter. Before the blowpipe is showing a yellow flame color, which is an indication of the sodium content.
Etymology and history
The name mirabilite goes back to the Latin word " sal mirabilis ", which means salt is amazing. Johann Rudolph Glauber (1604-1670), chose this name when he discovered an unknown salt in 1626 in the analysis of mineral water with a laxative effect. In 1658 he was able to produce artificially by the reaction of sodium chloride with sulfuric acid salt. After the discovery of natural sodium sulfate named Wilhelm Ritter von Haidinger the new mineral in 1845 the old term " sal mirabilis " mirabilite.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the mirabilite the mineral class of " sulfates, selenates, tellurates, chromates, molybdates and tungstates " belonged and there to the Department of " water -containing sulfates without foreign anions ", where he with syngenite the " mirabilite - syngenite group " with the system no. Formed VI/C.21 and the other members Eugsterit, Hydroglauberit, Koktait, Lecontit, Matteuccit, and Wattevillit.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the mirabilite also in the class of " sulfates ( selenates, tellurates, chromates, molybdates and tungstates ) " and then in the Department of " Sulfate ( selenates, etc. ) without additional anions, with H2O" one. This division, however, is further divided according to the relative size of the cations involved, so that the mineral is "With only large cations " to find according to its composition in the subdivision, where it forms the unnamed group 7.CD.10 the only member.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the mirabilite in the class of " sulfates, chromates and molybdates " and there in the department of " water -containing acids and sulfates " one. Here he can be found as the only member of the unnamed group 29.02.02 within the sub-division of " water -containing acids and sulfates (A ) 2XO4 • x (H2O) ".
Education and Locations
Mirabilite forms in evaporites under arid conditions. It crystallizes there from supersaturated sodium sulfate solutions, such as those found in saline springs or salt flats. Accompanying minerals are next thenardite among other things still Aphthitalit, Blödite, epsomite, gypsum, glauberite, halite and trona.
As a rather rare mineral form mirabilite can be abundant in part to different sites, overall it is not very common. So far (as of 2013) are around 180 localities known as.
In Germany the mineral among others, herring and Philippstal in the Hessian Werra was; at Hänigsen, Wath and on limestone Lüneburg in Lower Saxony; at Friedland in Mecklenburg- Vorpommern; found in the gypsum mine " Mathias " at Rammelsberg endeavor in Saarland and in the pit " Willi Agatz " at Dresden in Saxony.
In Austria mirabilite has to date held on especially in Salzburg, where he has been proven in several gypsum and salt mines or in thermal springs. In addition, the mineral is also found but in the penny Bach at Puchberg am Schneeberg in Lower Austria, in the salt mines of Altausee (Styria ) and Hall in Tyrol and Upper Austria at Bad Ischl salt mine in Hallstatt and in the rear Steiner Alp near Spital am Pyhrn in Upper Austria.
In Switzerland, mirabilite found so far in the gypsum mine at Birmenstorf in the canton of Aargau, in Martigny in the canton of Valais and the salt mines of Bex in Canton Vaud.
Known localities for mirabilite include the Tăuşoare Cave in Romania and the Death Valley National Park in the U.S. state of California. Other localities lie in Egypt, Antarctica, Argentina, Australia, Bolivia, Chile, China, England, France, Italy, Japan, Canada, Madagascar, Mexico, the Netherlands, Norway, Poland, Russia, Slovakia, Spain, Tajikistan, Czech Republic, Turkey, Turkmenistan, Ukraine, Hungary and other states in the United States.
Crystal structure
Mirabilite crystallizes in the monoclinic space group P21 / c ( Raumgruppen-Nr. 14) with the lattice parameters a = 10.51 Å, b = 10.37 Å, c = 12.85 Å and β = 107.8 °, and four formula units per unit cell.
Use
As a raw material
Mirabilite is a raw material for the production of soda.
In Medicine
Mirabilite is chemically identical with the Glauber's salt. Like this it can be used as a laxative ( laxative ) are used. In traditional Chinese medicine it is used as a laxative under the name Mang Xiao (芒硝) used.