Is andesite a Hypocrystalline?
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Is andesite a Hypocrystalline?
Vitro-porphyry Andesite Structure: hypocrystalline, porphyry-vitreous Texture: unoriented (massive), compact.
Where is trachyte found?
Trachytes are well represented among the Cenozoic volcanic rocks of Europe. In Britain they occur in Skye as lava flows and as dikes or intrusions, but they are much more common on the continent of Europe, as in the Rhine district and the Eifel, also in Auvergne, Bohemia and the Euganean Hills.
Is andesite a basalt?
Andesite is an extrusive rock intermediate in composition between rhyolite and basalt.
What type of igneous rock is andesite?
Andesite is a fine-grained, extrusive igneous or volcanic rock. It is dark grey and made up of equal amounts of light and dark minerals, although the crystals are too small to be seen without a magnifier. Occasionally andesite may contain some larger crystals.
What is Hypocrystalline?
Hypocrystalline is a textural term describing an igneous rock consisting of a mixture of glass and crystals where the ratio of crystals to glass is greater than 3:5. Rocks containing a higher ratio of glass are described as hypohaline or holohyaline.
What is Phaneritic and aphanitic?
APHANITIC TEXTURE – Igneous rocks that form on the earth’s surface have very fine-grained texture because the crystals are too small to see without magnification. PHANERITIC TEXTURE – Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber.
What is trachyte stone?
trachyte, light-coloured, very fine-grained extrusive igneous rock that is composed chiefly of alkali feldspar with minor amounts of dark-coloured minerals such as biotite, amphibole, or pyroxene. Compositionally, trachyte is the volcanic equivalent of the plutonic (intrusive) rock syenite.
What type of rock is andesite?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
What is andesite formed by?
Andesite is a volcanic rock. It is fine-grained because it forms by the rapid cooling of magmas usually when it erupts onto the Earth’s surface and forms lava flows. Andesite forms from magma that contains less quartz (silica) than rhyolite but more than basalt.
What is andesitic made of?
Andesite most commonly denotes fine-grained, usually porphyritic rocks; in composition these correspond roughly to the intrusive igneous rock diorite and consist essentially of andesine (a plagioclase feldspar) and one or more ferromagnesian minerals, such as pyroxene or biotite.
How Hypocrystalline is formed?
Hypocrystalline (or Hyalocrystalline). Rock composed of both crystals and glass. Indicates a period of relatively slow cooling (sufficiently slow to allow crystallization) followed by quenching of the remaining magma.
What is meant by aphanitic?
Aphanitic is a descriptive term for small crystals, and phaneritic for larger ones. Very coarse crystals (those larger than 3 centimetres, or 1.2 inches) are termed pegmatitic. In igneous rock.
What is the difference between aphanitic rocks and phaneritic rocks?
Rocks that are aphanitic have a grain size below 1 millimetre. On the other hand, phaneritic rocks have grains that are coarse and the grain size is usually between 1 millimetre and 10 millimetres.