Basanite (rock)
Basanite ( Latin basanite , modern Greek βασανίτης ) is a volcanic rock and belongs to the group of alkali rocks .
Word origin
The origin of the name is not entirely clear. One possibility is that the name was derived from the country Bashan , which is mostly mentioned in the Old Testament and is located in present-day Syria . Another possibility is the derivation from the Greek βασανίτης [λίθος] ( touchstone , very hard stone ), basanítēs [líthos] , " touchstone " or βάσανος , básanos , " grave stone".
composition
Plagioclase and feldspar representatives such as leucite and nepheline are predominant in the composition of basanite, and there are also proportions of augite , olivine and, more rarely, iron-titanium oxides such as ilmenite and magnetite . Smaller proportions of alkaline feldspars can also be present, which is illustrated by the position of the basanite in the line iron diagram . Augite and olivine are mostly present as intrusions in the matrix . The augite in this rock contains significantly more titanium , aluminum and sodium than in tholeiitic basalt . There is no quartz , but pyroxene and pigeonite .
From a chemical point of view, basanite only has a very low silicon oxide content of around 42 to 45 percent compared to basalt , but a high proportion of alkali oxides of 3 to 5.5 percent.
Basanite is located together with tephrite in field 14 of the route iron diagram and differs from tephrite in that it has an olivine content of more than 10 percent.
properties
Basanite has a red-brown to black-gray color. Due to its high density and strength , the stone has a high resistance to polishing, as well as a high resistance to pressure and impact. It is also weather and frost resistant. However, it is not resistant to chemical aggressions.
Subspecies
Nepheline basanite
In addition to the essential components of feldspar, nepheline and augite, nepheline basanite has some olivine content, but does not contain any leucite. It consists of a reddish-brown or gray-brown glassy or microcrystalline base material in which there are fragments of olivine and clinopyroxene . The olivine is a few millimeters in size and is mostly only present in weathered form, either as yellowish limonite or as red hematite . A well-known representative of a nepheline basanite is Limburgite .
Leucite basanite
Leucite basanite is very closely related to nepheline basanite. The only difference between the two rocks is that it has no nepheline, but leucite.
use
In ancient Egypt , statues were made from black basanite. Today, due to its properties, Basanit is used in road and path construction , in the concrete industry and in track and hydraulic engineering .
Occurrence of basanite
Basanites can be found both on the continents and on islands by the sea. They arise, for example, together with basalts through hotspot volcanism in Hawaii or the Comoros .
Central Europe
Outside of Central Europe
- France - Chaîne des Puys , Chaîne de la Sioule
- Hawaii
- Comoros in the Indian Ocean
- Madagascar
- Wadi Hammamat in Egypt
Web links
Individual evidence
- ↑ Basanite. Dr. Olaf Otto Dillmann, accessed April 19, 2010 .
- ↑ Basanite. Rhenish provincial basalt u. Lavawerke GmbH & Co. OHG, accessed on April 19, 2010 .
- ^ Herder's Conversations Lexicon . tape 1 . Herder, Freiburg im Breisgau 1845, p. 417 f . ( Digitized version ).
- ↑ Robert Buchwaldt, Robert Tucker, Robert F. Dymek, Robert E. Criss: Geochemiry and petrology of a miocene trachyte-basanite suite from Mt. Tsaratanana, northern Madagascar. 2003, accessed April 19, 2010 .