What is andesite texture?

What is andesite texture?

It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs.

Does andesite have a vesicular texture?

A related texture is amygdaloidal in which the volcanic rock, usually basalt or andesite, has cavities, or vesicles, that are filled with secondary minerals, such as zeolites, calcite, quartz, or chalcedony. Rock types that display a vesicular texture include pumice and scoria.

What is andesite composed of?

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.

How do you identify andesite?

ANDESITE is the fine- grained equivalent of DIORITE. It tends to be a darker gray than rhyolite and is often porphyritic, with visible hornblende. BASALT occurs as thin to massive lava.

Is andesite a real mineral?

What is Andesite? Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. They have a mineral composition that is intermediate between granite and basalt.

Is andesite a real rock?

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.

What causes vesicular texture?

A vesicular texture is caused when dissolved gases and other volatile components of a magma erupt from the liquid portion due to a decrease in pressure. This causes the magma to foam up, and the resulting rock to be riddled with hole-like structures called vesicles.

What is a use for andesite?

Andesite may be used as aggregate or fill, but it is not ideal for concrete applications because it is high in silica, and causes alkali-silica reactivity in the concrete. Andesitic volcanism is associated closely with porphyry copper deposits and it is a host rock for much of the world’s copper ore.

Is andesite phaneritic or aphanitic?

Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 10% feldspathoid by volume, with at least 65% of the rock consisting of feldspar in the form of plagioclase.

What is the color of an andesite rock?

Andesite is volcanic rock named after the Andes Mountains. Intermediate in silica content, it is usually gray in color and may be fine-grained or porphyritic. Andesite is the volcanic equivalent of diorite. May 21 2019

What is andesite luster?

Andesite is a brown or greyish volcanic rock that forms thick lava. The luster of a rock is non-metalic. 0.0.