Neuburg Siliceous Earth
Neuburg Siliceous Earth is a natural mixture with predominant proportions of the finest silica particles and 20 to 40 percent by weight of kaolinite .
The world's only known deposits with this unique composition are located near Neuburg an der Donau . Due to its purely mineral origin, Neuburg Siliceous Earth is not diatomaceous earth, commonly referred to as silica or kieselguhr , which has a biological origin and arose from diatoms. Today, only one mining company, Hoffmann Mineral GmbH in Neuburg an der Donau , deals with the mining of Neuburg Siliceous Earth . Around 55,000 tons of the processed mineral are sold every year. For this, 120,000 t of raw silica must be extracted. After gentle suspension in well water, the finest proportion of the silica is separated using hydrocyclones . Neuburg Siliceous Earth is used as a high-quality functional filler or as a polishing agent in many industrial applications. Because of its purity, it is also suitable as a dietary supplement.
geology
The Neuburg Siliceous Earth was formed about 93 to 98 million years ago in the Cenomaniac , the lowest level of the Upper Cretaceous (Cretaceous Period) in a sea bay in what is now the find area, when the finest sediments from weathered granitic masses of the northern Upper Palatinate were deposited. The key fossil is Inoceramus crippsi .
mineralogy
Neuburg Siliceous Earth was probably formed as a mixture of minerals. It essentially consists of the finest particles of cryptocrystalline (appearing amorphous, particles smaller than 1 micrometer) and amorphous silica with a total of 60 to 80 percent by weight, otherwise of lamellar (platelet-shaped) kaolinite. Contrary to earlier assumptions, the silica content is not quartz, since essential properties of the quartz are missing, but a special SiO 2 modification. Influences from the nearby Ries event are discussed, the meteorite impact that led to the formation of the Nördlinger Ries.
Finding of deposits
The Neuburg Siliceous Earth was found in funnels and cracks in the Jura limestone below. Certainly, people have always been aware of deposits close to the surface, as some of them only had a small amount of soil. The deposits that remain today are mostly located under young geological layers at a depth of five to twenty meters. In the past, exploration was carried out by pulling drill cores with hand tools; today, machine boreholes convey crushed drill cuttings continuously and much more cheaply, whereby the silica can be clearly distinguished from earth and limestone on site and without special analysis.
Dismantling
The Romans used the Neuburg Siliceous Earth for refractory linings of kilns and for pottery. The material was only recovered in a targeted manner around 1830. Chemists discovered the formula for the production of the extremely expensive pigment ultramarine blue , for which the Neuburg Siliceous Earth was very well suited as a natural raw material. Until well into the 19th century, the near-surface deposits were mainly extracted in open-cast mining. From the end of the 19th century, more and more deposits were developed underground, as it was often easier to dig through thicker layers of earth than to completely remove them. During the underground mining, however, large parts of the deposits could not be used because, for structural reasons, valuable material had to remain untouched. Therefore, the modern, efficient opencast mine finally replaced the underground mine with the closure of the last underground mine in 1979. In modern open-cast mining, backhoe excavators not only remove the layers of overburden quickly, they also have the enormous tearing forces to break out the raw material. Blasting is rarely necessary.
Recultivation and renaturation
The mining of Neuburg Siliceous Earth is an encroachment on nature, which is offset by recultivation and renaturation. After the mining of a deposit has been completed, the large craters are filled with excavated material, sand and other rock that were separated during processing. For a vegetation with forest or for the purpose of agricultural cultivation, layers of humus are applied last. In addition, ecologically valuable wetlands are regularly created during mining. Such biotopes are specifically preserved even after mining has ended. Threatened species such as the yellow-bellied toad (Bombina variegata), tree frog (Hyla arborea), pond newt (Triturus vulgaris), mountain newt (Triturus alpestris) and crested newt (Triturus cristatus) find their habitat and spawning grounds in them.
processing
First, the raw material is slurried in a lot of well water. The finest portion that can be used is obtained in successive physical separation processes by centrifugation in hydrocyclones . The excess water is then separated off and pressed out, and finally the material, which is concentrated on moist filter cake, is gently brought to powdery final quality in natural gas-operated dryers.
use
Ultramarine blue
It was first used in modern times around 1830, when ultramarine blue was preferably produced in Germany on the basis of Neuburg Siliceous Earth. Before that, very expensive semi-precious stones (lapis lazuli) were required. This groundbreaking invention of the simple production in the melt flow from aluminum-containing silicate, sulfur and other ingredients brought the Neuburg Siliceous Earth a rapid upswing because it was ideally suited as a raw material because of its almost ideal composition and great fineness. This once important use is no longer relevant today.
Polishes
A long tradition since the second half of the 19th century has the still widespread use as abrasives in polishing agents and household cleaners. Acetic acid polishes are very easy to produce because of the acid resistance of Neuburg Siliceous Earth and the naturally good polishing properties.
filler
Today, Neuburg Siliceous Earth is mainly used as a filler for polymers. This application began in the 1920s with the widespread introduction of rubber goods. The loose powder is characterized above all by the ease with which it can be mixed in and the small grain size. Automobile hoses, floor coverings and roofing membranes for the construction sector contain high proportions of this filler. In the paint and varnish industry, electrophoresis and anti-corrosion coatings are important fields of application. Due to its purity, Neuburg Siliceous Earth can be used in materials for food-related areas.
Food supplements
Because of the silicic acid and trace elements that can be easily digested in the digestive tract, as well as the processing that is gentle on the natural properties and the purity, Neuburg Siliceous Earth is also suitable as a food supplement .
Individual evidence
- ^ J. Göske, W. Kachler: Morphology, Physicochemistry and Phase Analysis of Neuburg Siliceous Earth . Microscopy and Analysis 22 (5): 23-24 (EU), 2008
literature
- Schönrock, Dirk: Neuburg Siliceous Earth. Extraction, refinement, applications as a functional filler . The library of technology, vol. 308, Süddeutscher Verlag onpact, Munich 2008, ISBN 978-3-937889-77-1
Web links
- Bavarian State Ministry for Economic Affairs, Infrastructure, Transport and Technology: Map Raw Materials Bavaria (PDF file; 819 KB)
- Hoffmann Mineral