Phosphorite
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Phosphorite is a marine sedimentary rock that occurs in layers with other marine rocks, mostly limestone.
Rock description
Phosphorite consists of a mixture of apatite and organic components. The organic components are often recognizable. If phosphorites are cracked, a putrid smell escapes in many cases. If not rearranged, they are connected with limestone , green sand or green sandstone .
Phosphorites occur as grape-shaped tubers, crusts and concretions in marine clays. The phosphorite grains form bulging and bulbous surfaces, the mineral content is not visible to the naked eye. They are black, rarely brown rocks.
Mineral inventory
The main components are the minerals carbonate - fluoroapatite (Ca 5 [(F, OH, CO 3 ) / (PO 4 ) 3 ]), which is mainly of organic origin, and calcite . Phosphorite is often found in conjunction with green glauconite .
Emergence
Phosphorites are mainly formed in the shallow sea near the outer edge of the shelf , where cool, phosphate-rich seawater flows up. Since the solubility of the phosphate depends on the temperature and more phosphate is soluble in cold water, the phosphate is bound by chemical and biological processes.
The predominantly biological formation of phosphorite in terms of quantity occurs in various ways. A large part of the phosphorites arise from the accumulation of phosphorus in phytoplankton and animal excrement or the installation in hard parts such as bones and chitin armor. Some occurrences are considered to be metabolites of sulfur bacteria.
The chemical formation of phosphorites can be traced back to direct precipitation from sea water or to the metasomatic incorporation of phosphate in calcareous sediments. The dissolution and reprecipitation of phosphate plays an important role in the formation of secondary phosphorite deposits. An example of the very different processes associated with this is the formation of phosphorites in areas with high levels of precipitation from guano , or the phosphorization of karstified Devonian limestones in the Lahnmulde in the Rhenish Slate Mountains .
use
The rock phosphorite is used as a raw material for the production of phosphorus, especially for fertilizer production and in the chemical industry . Well-known occurrences of phosphorite - partly in concretions - can be found on Nauru (almost exhausted), in Morocco , Florida , Tunisia , Estonia and Algeria .
In Germany there is a phosphorite tuber horizon near Leipzig . The extraction of phosphorite used to be frequent in the area between Wetzlar and Katzenelnbogen , the extraction of these Lahn phosphorites took place mainly between 1865 and 1890. These presumably tertiary phosphorites were extracted, for example, from the Zollhaus mine in the municipality of Aar-Einrich .
literature
- Ferdinand Bernauer: The phosphorites of the Lias of German Lorraine . In: Yearbook of the Prussian Geological State Institute . Vol. XL, Part I, No. 1, 1919.
- Geology and hydrothermal mineralization in the slate mountains on the right bank of the Rhine . In: Thomas Kirnbauer (Ed.): Yearbook of the Nassau Association for Natural History . Special volume 1. Nassau Association for Natural History, Wiesbaden 1998, ISBN 3-00-003218-5 .
- Dieter Richter: General Geology . 3. Edition. de Gruyter Verlag, Berlin - New York 1985, ISBN 3-11-010416-4 , pp. 178 .
- Roland Vinx: Rock determination in the field . 2nd Edition. Springer-Verlag, Berlin, Heidelberg 2008, ISBN 978-3-8274-1925-5 .