Potash salt

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Potash salt or potash for short is a fossil deposit of various salt minerals with a high content of potassium compounds .

Typical minerals in potash are:

Of these, potassium chloride (sylvine) and magnesium sulfate (kieserite) are used economically.

In contrast to the usually colorless rock salt , which consists almost exclusively of halite , potash salt often has an orange-red to light brown color, caused by embedded iron oxides and hydroxides . According to the main ingredient, a distinction is made between kieseritic, sylvinitic and carnallitic potassium salt. Most of the deposits mined worldwide have a raw material with a sylvinite or carnallite character. There are extensive Kieserite deposits mainly in Germany.


Salt layers in the Zechsteinsalinar of Sondershausen, tectonically deformed

The potash salt deposits in Central Europe were formed a good 250 million years ago in the Zechstein ( Oberperm ) and Tertiary (Upper Rhine Rifts: Wittelsheim Basin in Upper Rhine and near Buggingen in South Baden). In the area of ​​today's potash deposits there were shallow marginal seas (so-called epicontinental seas ) or inlets and the climate in the region was dry and hot , which allowed a lot of sea water to evaporate in a relatively short time. As a result of tectonic movements, these seas or inlets were sealed off from the open ocean, so that they began to dry out. From such an increasingly salty body of water, the following substances crystallize one after the other according to their solubility:

  1. Limestone / dolomite ,
  2. Gypsum / anhydrite (evaporation to at least approx. 25% of the initial amount),
  3. Rock salt (evaporation to at least approx. 10% of the initial amount),
  4. Potash salt (evaporation to less than 1% of the initial amount)

In most cases, however, this deposition sequence was interrupted or ended at the stage of gypsum or rock salt deposition due to the disappearance of the barrier or a change in climate. Potash deposits are therefore relatively rare. The salt sequence once crystallized out was subsequently covered by other sediments (e.g. clay ). Often, however, the favorable conditions for dehydration reappeared and evaporation and separation began again. The simultaneous, slow, continuous subsidence of the sea basin subsoil could form layers of gypsum and salt up to several thousand meters thick over the course of several million years. In the Zechstein Basin in the underground of Central and Western Europe, at least five such series are distinguished, which are also called Zechstein cycles. Three of these cycles (called Werra , Staßfurt and Leine ) contain layers of potash.

At some point, however, the climatic or geographical conditions changed permanently so that no more salts were deposited. The deposition of other sediments (for example sand , which subsequently solidified into sandstone ) continued and so the salt was again covered by layers of rock thousands of meters thick.

But since salt has a lower density than most other rocks and also begins to flow slowly under pressure, it collected in certain places and began to rise from there towards the surface of the earth. In this process, known as halokinesis , salt cushions, walls and sticks were ultimately created . So the potash salt came together with the rock salt near the surface, where it is now accessible to humans and can be extracted in mines .


Sylvinite sample with white and blue halite and small reddish sylvine fragments from the Uralkali mine SKRU-2 in Solikamsk , Perm region , Russia.

The largest potash salt deposits outside Germany are found in Russia , Belarus and the Ukraine , in Canada , the USA and in the Chinese Lop Nor . Israel and Jordan also extract significant quantities from salt lakes such as the Dead Sea . The German deposits are in the Gorleben - Braunschweig - Hanover area in Lower Saxony , in the Altmark and the Griesen area , in the Magdeburg - Halle area in Saxony-Anhalt ( Zielitz ) and in Südbad (closed since the 1970s), in Solling , Süd Harz (closed) and Dün and in the Werra - Fulda area in Hesse and Thuringia ( Neuhof-Ellers , Werra potash district with plants in Heringen , Philippsthal and Unterbreizbach ).


Potash salts are mined in Germany in underground mines .

The mining extraction is carried out either by conventional drilling and blasting work or mechanically by means of partial and full cut machines .

All over the world there are attempts to extract potash salts (Carnallite) similar to rock salt by means of borehole brine (hot leaching). Such a brine mining takes place z. B. in Bleicherode instead.


Aerial view of the spoil dump (right in the picture) of the Sigmundshall potash mine in Bokeloh near Hanover .

Since the raw salt has an average recyclable content of 20 to 35 percent, processing in above-ground factories is necessary. Flotation , hot dissolution or electrostatic separation can be used as treatment processes . Depending on the processing method, the product is then dried and refined, for example by granulation .

A major difficulty lies in the disposal of the residual liquors with high contents of magnesium salts and sodium chloride that arise during processing. Some of these are pressed into porous layers of the upper shell limestone , and some of them go into the receiving waters as waste water (e.g. Werra).


Potash salts are mainly processed into mineral fertilizers . Potash fertilizers are usually more than 90 percent pure. Because this corresponds to a potassium content of around 60 percent, it is also known as "60s potash". The highly pure 99 potassium chloride or industrial potash is used in the chemical industry and medicine. In the case of chloride-sensitive agricultural plants, fertilizer is used, which mainly consists of potassium sulfate.

Effect as a fertilizer

The mineral potassium is a main nutritional element in plant nutrition and strengthens the metabolic processes in plants: photosynthesis is intensified, the conversion of grape sugar (glucose) into starch and the build-up of protein are accelerated. This promotes the growth of the plants.

The K + ion is the most important ion in the plant's metabolism for increasing osmotic pressure and swelling. Sufficient potash fertilization causes the plant to adapt better to drought and increases frost resistance . The stability of the plants is indirectly improved. Potassium deficiency leads to wilting , chlorosis on older leaves and death from the leaf edge (marginal necrosis).

See also


  • Walther E. Petrascheck & Walter Pohl: deposit theory . 3. Edition. E. Schweizerbarth'sche Verlagsbuchhandlung, Stuttgart 1982, ISBN 3-510-65105-7 .
  • Otto F. Geyer, Manfred P. Gwinner: Geology of Baden-Württemberg . 3. Edition. E. Schweizerbarth'sche Verlagsbuchhandlung, Stuttgart 1986, ISBN 3-510-65126-X .
  • Ludwig Baumann, Igor Nikolskij, Manfred Wolf : Introduction to geology and exploration of deposits . 2nd Edition. VEB German publishing house for basic industry, Leipzig 1979.
  • Wilfried Hacker: Geosciences and mining history in the three-country region of Hesse, Thuringia and Lower Saxony . tape 2 . Universitätsverlag Göttingen, Göttingen 2007, ISBN 978-3-940344-03-8 ( PDF ).

Web links

Individual evidence

  1. Data sheet 60er Kali , K + S AG.
  2. KALISOP data sheet  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. K + S Germany GmbH.@1@ 2Template: Dead Link / datasheets.k-plus-s.com