Andesite


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andesite

[′an·də‚zīt]
(petrology)
Very finely crystalline extrusive rock of volcanic origin composed largely of plagioclase feldspar (oligoclase or andesine) with smaller amounts of dark-colored mineral (hornblende, biotite, or pyroxene), the extrusive equivalent of diorite.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Andesite

 

an extrusive, dark-colored (such as dark gray, brown, or black) mountain rock. Its structure is porphyritic or hyalopilitic; in the latter case the microlites resemble felt saturated with glass. It is formed as a result of the freezing, at the top surface or close to it, of volcanic lava containing 56–60 percent silicic acid and much magnesium, calcium, and iron. Andesite is usually a fresh rock composed of crystals of medium plagioclases, andesine, and pyroxenes and less frequently of magnetite, hornblende, and other minerals immersed in glass. Andésite is widely spread throughout contemporary and ancient volcanic regions such as Kamchatka, the Caucasus, Middle Asia, and the Mediterranean. Together with basalt, it constitutes the principal mass of extrusive rocks. It is used as an acid-proof material and for special glazing.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
For the air-dried and wet Emochi andesite and Jingkou sandstone samples, the average slope of the line AB is calculated as [E.sub.d] when the stress-strain curves become horizontal after the decrease in the stress in the postfailure region.
The results presented here include analyses of unaltered host rocks (andesites), analyses of fumarolic sulfur, analyses of sulfur leachates, and the SEM-EDS analyses of rare mineral inclusions in sulfur.
Prospecting in 2015 focussed on a highly siliceous gossanous andesite outcrop with azurite/malachite oxidation and possible tetrahedrite.
The Podmokly area is characterized by andesite, siltstone and loess.
The parameters used for numerical simulation are: Sanjome andesite k = 6.541 GPa, r = 3.355 GPa, A = 1.388e-4, B = 3.211e-7; Tako Sandstone k = 3.297 GPa, r = 1.691 GPa, A = 1.917e-4, B = 6.137e-7; Kimachi Sandstone k = 3.531 GPa, r = 1.810 GPa, A = 2.165e-4, B = 7.828e-7.
These high-degree, crust-derived partial melts are the source of tholeiitic andesites and basalts that cause summit eruptions at volcanoes in the NE Japan arc.
IIAa 4 (7.8) 5 2.5 (180) Andesite IIIAa 5 12.5 4 1.8 200 Andesite IIIAa 6 (7) 3.8 1.5 (100) Andesite IIIBb 7 14.5 4 1.8 250 Andesite IIIBb 8 18.5 4.7 2.1 340 n.d.
The stone used in the construction of the structure is roughly cut andesite, except for the arches, which are made from clay brick with a thick mortar.
Sites range from single modified stones to large-scale complexes of andesite "seats" and "tables", mortars, cooking places, grinding stones and carved boulders (for stone feature types, see Table 1).