Blödite

• Astrakanite
• Simonyit

Blödite is a rarely occurring mineral from the mineral class of sulfates (including selenates, tellurates, chromates, molybdates and tungstates ). It crystallizes in the monoclinic crystal system with the composition Na2Mg [ SO4 ] 2.4 H2O, is thus seen chemically a hydrous sodium magnesium sulfate

Blödite usually develops short prismatic crystals with glass-like sheen on the surfaces, but also comes in the form of granular to massive mineral aggregates before. In its pure form it is colorless and transparent. But it may also appear white and accept by foreign admixtures a dark gray, bluish- green or reddish color by multiple refraction due to lattice defects or polycrystalline training, the transparency decreases accordingly.

Special Features

Blöditkristalle need to be kept under wraps because they (similar to Chalkanthit ) with time weather in the air by removing water and form a white crust. Furthermore, the material is slightly soluble in water.

Etymology and history

Blödite was first discovered and described in 1821 named in Bad Ischl salt mountain in Upper Austria's Salzkammergut region of Johann Friedrich John ( 1782-1847 ), of the minerals by the German chemist Karl August Stupid ( 1773-1820 ).

1869 described the Austrian mineralogist Gustav Tschermak ( 1836-1927 ), a newly discovered mineral, and gave him in honor of the Austrian scientist Friedrich Simony name Simonyit. In later studies, however, revealed that the new mineral was identical to the Blödite already known, so that the designation Simonyit has been discredited and is now considered a synonym for the Blödite.

The term astrakanite (also Astrachanit ) coined Gustav Rose in 1837 for the white, opaque and prismatic crystals that he found at the Volga estuary near the city of Astrakhan in Russia in 1937 .. This, however, later also prepared out as Blöditkristalle.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Blödite belonged to the department of " hydrous sulfates without foreign anions ", where he together with Changoit, Konyait, Leonit, Mereiterit and Nickelblödit the " Leonit group " with System no. VI/C.18 formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Blödite also in the department of " sulfates ( selenates, etc. ) without additional anions, with 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 subdivision " with medium -sized and large cations " where there the eponymous " Blöditgruppe " with the system no. Forms 7.CC.50 and the other members Changoit and Nickelblödit.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Blödite in the class of " sulfates, chromates and molybdates " and then in the Department of " Water-containing acids and sulfates " one. He is also named as the " Blöditgruppe " with the system no. 29/03/03 to find within the subdivision " water containing acids and sulfates (A ) 2B ( XO4 ) 2 × x (H2O) ".

Education and Locations

Blödite formed by chemical sedimentation in salt waters, ie by evaporation- induced precipitation of Blödite forming molecular groups. Accompanying minerals occur among others, carnallite, halite, kainite, mirabilite, thenardite and polyhalite.

A rare mineral formation Blödite could be proven so far only in a few localities, of which approximately 80 localities (as of 2013) are considered to be known. Apart from its type locality Bad Ischl salt mine the mineral nor entered into Austria in the community Abtenau ( Webing ), in Gipswerk Moldan at Grubach and the rock salt deposit Duerrenberg in Salzburg and in the salt mines at Hall in Tirol and Hallstatt in Upper Austria on.

In Germany Blödite could inter alia, Giesel, Neuhof, herring and Philippstal in Hesse; the pit "Julia" at Herne in North Rhine -Westphalia; at Tarthun and Westeregeln in Saxony -Anhalt; be found in the pit, "Willi Agatz " at Dresden in Saxony and Thuringia marker.

Other localities lie among other things in Antarctica, Australia, Chile, China, Canada, France, Iceland, Hungary, Italy, Mexico, Namibia, Pakistan, Poland, Russia, Turkey, Turkmenistan, Ukraine, Uzbekistan, and in several states the United States.

Crystal structure

Blödite crystallizes in the monoclinic space group P21A (14 ) with the lattice parameters a = 11.126 Å; b = 8242 Å; c = 5.539 Å; β = 100.84 ° and α = γ = 90 ° and two formula units per unit cell.