Phonolite
Phonolite (Greek φωνή 'sound', λίθος 'stone' to German phonolite due to the bright sound when struck ) is a volcanic rock of greenish to gray color. The structure is often porphyritic, with alkali feldspar and Foidminerale occur as phenocrysts in a dense, fine-grained groundmass. One variety that contains the basic mass much rock glass is referred to as Kenyit. Phonolite belongs to the group of alkaline rocks.
Description of rock and mineral composition
The color of these rocks is brownish to gray. They are fine-to coarse-grained and in the uniformly colored matrix are phenocrysts. You have a porphyritic texture. In the quarry the rock is mostly secreted platy.
The main components are high temperature alkali feldspar ( sanidine ), one or more minerals from the group of Foide and at low levels (0 to 10 percent by volume ) plagioclase. The most common Foidmineral is nepheline ( phonolite sensu stricto ), but in addition can also leucite, sodalite, Haüyn and other rarer Foide occur in considerable quantity. As mafic minerals occur aegirine, Ägirinaugit, Alkaliamphibole, olivine to ( fayalite ), Melanite and biotite. Frequent Nebengemengteile and accessory minerals are sphene and apatite, something rarer are zircon, magnetite and perovskite. Also phonolites with plenty of wollastonite are also known. Frequently contains phonolite secondary minerals from the group of zeolites, such as chabazite or natrolite. In the classification diagram of Streckeisen phonolite is in the field 11 With increasing Plagioklasgehalt he goes to the phonolite tephrite, with increasing Foidgehalt in the phonolite Foidit. The plutonic rock equivalent is the Foidsyenit.
Occurrence
Phonolite is a common volcanic rock and occurs worldwide, associated with other alkaline rocks such as tephrite, Foidit, Melilithit and carbonatite on. As this is phonolite a typical product of intraplate volcanism. Phonolitic magma is often promoted by explosive volcanism on the Earth's surface and forms pyroclastic deposits, lava flows, domes and near surface hardened gears and intrusions.
Deposits in Europe are, for example, in the Zittau Mountains ( Listen ), ( width Mountain ), in the Eifel ( Laacher See volcano), in the Rhön, the emperor chair ( eg: with Bötzingen ), Hegau and in the volcanic Massif Central in France. Other known occurrences are the Devils Tower in Wyoming, USA, in the area of the East African grave breach and the Canary Islands.
The phonolites often have local names, such as Viterbit in Umbria, Selbergit in the Eifel, Sommait at Vesuvius near Naples in Italy and Katzenbuckelit in the Odenwald.
Use
Phonolite is widely used as ballast material and natural stone wall, further as facade panels. The resulting pyroclastic deposits from phonolite - Tuff is used because of its porous structure as lightweight building blocks. It is easy to form and cut and therefore is also used for sculptures. Zeolitic phonolites with pozzolanic properties are mined throughout the world as an aggregate for the cement and concrete production. In Germany is made from Römertuff in the Eifel tuff, the special mortar is mixed with hydraulic properties. The phonolite from Bötzingen is also processed to mud.
Types of natural stone
Some commercial varieties:
- Ettringer tuff, Ettringen in the Eifel
- Weiberner Tuff (also called Flötenstein ), women in the Eifel
- Römertuff, near the Laacher See
- Peperino, Viterbo, Italy