What determines the texture of an igneous rock quizlet?
The texture of an igneous rock is determined by the cooling history of the magma from which it formed. Magmas that cool slowly form large crystals, and those that cool quickly form small crystals. Define phaneritic texture. Phaneritic texture describes coarse grained rocks.
What are the texture of igneous rocks?
Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. The six main types of textures are phaneritic, aphanitic, porphyritic, glassy, pyroclastic, and pegmatitic.
What determines a rocks texture?
The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock's extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.
What determines the color of an igneous rock?
The color of igneous rocks is generally given by the amount of ferromagnesian minerals. In the specific case you are questioning, rhyolites similar to andesites in color, the magma composition will dictate it.
Which of the following is a factor that determines the grain size of an igneous rock?
In most cases, the resulting grain size depends on how quickly the magma cooled. In general, the slower the cooling, the larger the crystals in the final rock.
How do you describe igneous textures?
The texture of an igneous rock made up entirely of crystals big enough to be easily seen with the naked eye is phaneritic. Phaneritic texture is sometimes referred to as coarse-grained igneous texture. Granite, the most well known example of an intrusive igneous rock, has a phaneritic texture.
What are the textures and structures found in igneous rocks?
The rapid cooling of lava/melt molten rock on the surface of the Earth produces fine grained minerals or glass. The igneous rocks vary in grain size from very coarse, medium to fine grained or even glassy in hand specimen and under the microscope. Thus, igneous rocks display variety of textures.
What are the structure and texture of igneous rock?
An igneous rock is any crystalline or glassy rock that forms from cooling of a magma. A magma consists mostly of liquid rock matter, but may contain crystals of various minerals, and may contain a gas phase that may be dissolved in the liquid or may be present as a separate gas phase.
What characteristics are used to identify igneous rocks?
Two main characteristics are used to classify igneous rocks: 1) texture (the size of the mineral grains in the rock; and 2) composition (often determined by what the actual minerals are).
Does the texture of an igneous rock determines the color of the rock?
Explanation. The color of the rock is often influenced by its mineral composition. For example, if a rock has a light color, then it contains a high percentage of silica. Moreover, it has a lot of quartz and feldspar, which are the minerals that give off white color.
What can you tell about an igneous rock that has a fine texture?
Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. These tiny crystals can be viewed under a petrographic microscope (1).
What are the differences in the textures of igneous rocks?
Texture is comprised of grains, and there are a few main types of igneous rock grains: Equant grains are those with boundaries of equal lengths; rectangular tablet shapes are known as tabular grains; acicular grains are slender crystals; long fibers are known as fibrous grains, and a grain that is prismatic is one that …
What causes a glassy texture in igneous rocks?
If a rock looks like a block of (colored) glass, with no visible mineral crystals, it has a glassy texture. Superficially, a glassy texture suggests cooling that was so extremely fast that no crystals could form.
How is an igneous rocks color determined?
The color of igneous rocks is generally given by the amount of ferromagnesian minerals. In the specific case you are questioning, rhyolites similar to andesites in color, the magma composition will dictate it.
What is the texture and composition of igneous rocks?
Igneous Rocks: textures and compositions
| Felsic | Intermediate | |
|---|---|---|
| Coarse- grained | granite | diorite |
| Fine- grained | rhyolite | andesite |
| Minerals | quartz, K-feldspar, amphibole, muscovite, biotite | plagioclase, quartz, amphibole |
Feb 23, 2005
What are the factors that you should consider when classifying igneous rocks?
Among them are:
- Minerals Present in the Rock (the mode). The minerals present in a rock and their relative proportions in the rock depend largely on the chemical composition of the magma. …
- Texture of the Rock. Rock texture depends to a large extent on cooling history of the magma. …
- Color. …
- Chemical Composition.
Jan 11, 2011
How is the texture of an igneous rock related to the rate at which it cooled?
There are two fundamental properties of igneous rocks that are used to assign a name. Texture — the size of the crystals can be crudely related to the rate of cooling. The higher the rate of cooling the smaller the size of the crystals.
How igneous rocks are classified based on formation and texture?
Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.
How can you use texture to determine whether an igneous rock is intrusive or extrusive?
Intrusive igneous rocks cool from magma slowly because they are buried beneath the surface so they have large crystals. Extrusive igneous rocks cool from lava rapidly because they form at the surface so they have small crystals. Texture reflects how an igneous rock formed.