Tephrite

Tephrite ( tephra Greek = ash) are reddish brown to black, gray igneous rocks showing a same - grained porphyritic to fine-crystalline structure. Phonolithische Tephrite, sometimes called Phonotephrit are somewhat brighter.

  • 5.1 Notes and references

Description of rock and mineral composition

Tephrite consist of feldspar ( nepheline or leucite ), anorthitreichem plagioclase ( An50 -70), clinopyroxenes, amphiboles and subordinate alkali feldspars.

Olivine not come or still only a fraction smaller than 10%. In this capacity, the Tephrite differ from the olivinreicheren Basaniten that are in the same field of Streckeisen diagram ( QAPF classification). Tephrite are related in their conditions of origin and in their appearance with the basalt, with which they are often associated.

Tephrite have few or no phenocrysts. In contrast, rock pores are often included, where can Zeolithminerale occur. Peridotitische xenoliths do not occur.

In everyday language, the term tephrite is hardly used, the rock is commonly referred to as basalt.

History

Tephrite in 1816 for the first time by Pierre Louis Antoine Cordier in the Journal des Mines (Vol. XV) scientifically described. Cordier was a French geologist who examined volcanic rocks. Further work to carried out later by Karl Wilhelm von Fritsch and tear under their rock researches on Tenerife (1868 online).

Occurrence

Tephrite occur in moderate or of columnar form as lava flows. However, they also act as slag and pyroclastic secretions.

In Germany Tephrite see the Eifel (such as Mayen basaltic lava ), Lusatia, in the Westerwald, the emperor chair, Vogelsberg and in the Rhön. Other occurrences are, for example, from the Canary Islands and Madagascar, from Italy, Portugal, Greenland, Uganda, Kazakhstan and Colorado known.

Use

Individual Tephrite be used as flooring, block steps and facade panels.

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