What are the 3 textures of igneous rocks?
Igneous Rock Textures 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.
What is the texture of a fine grained igneous rock?
aphanitic 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.
What are common textures 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.
Why do igneous rocks have different textures?
Explanation: The faster the magma cools that smaller the crystals that are formed. Some magma from which the igneous rocks is form come from different combinations of remelted igneous rocks, metamorphic rocks and sedimentary layers. The different sources of the melted material affects the textures of the igneous rocks.
How is the texture describe if an igneous rocks?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals. In addition to texture, igneous rocks may are classified according to their chemical composition.
Where do igneous rocks with a fine grained texture form?
The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don’t have much time to grow, so these rocks have a very fine-grained or even glassy texture.
How is the texture describe if an igneous rock?
Igneous rocks are rocks formed from the crystallization of a liquid (molten rock). Magmas and their resultant plutonic rock bodies cool and crystallize slowly and are characterized by coarse-grained texture, in which the mineral crystals are visible to the unaided eye.
What do igneous rock textures say about the rock that formed?
The igneous texture tells us how the magma cooled and solidified. Magma can solidify into igneous rock in several different ways, each way resulting in a different igneous texture. Magma may stay within the earth, far below ground level, and crystallize into plutonic igneous rock (also known as intrusive igneous rock).
What does igneous rocks look like?
Extrusive, or volcanic, igneous rocks look dull and do not sparkle much because they are fine grained. These crystals make a coarse-grained igneous rock called plutonic, or intrusive, igneous rock because the magma was intruded into cracks deep under the earth’s surface.
Where do igneous rocks with a coarse grained texture form?
Intrusive rocks have a coarse grained texture. Extrusive Igneous Rocks: Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface. These are the rocks that form at erupting volcanoes and oozing fissures.
What are the different types of igneous rock textures?
There are nine main types of igneous rock textures: Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic, equigranular, and spinifex. Each kind of texture has a variety of different characteristics that make them unique. What determines igneous rock texture? It all comes down to the rate at which the rock cools.
What do you mean by texture of rock?
Texture is the intimate mutual relationship of the constituents of rock. That is, it deals with size, shape, nature and arrangements of igneous rocks. Texture is best studied in thin section under microscope rather than in the outcrop. Required considerable factors for the description of texture 1.
What kind of igneous rock has no grains?
Black Obsidian. James St. John/Getty Images. Glassy (or hyaline or vitreous) rocks have no or almost no grains at all, as in this quickly chilled pahoehoe basalt or in obsidian. Pumice is another type of igneous rock with a glassy texture.
What kind of rock has a glassy texture?
Pumice is another type of igneous rock with a glassy texture. Phaneritic (“FAN-a-RIT-ic”) rocks have mineral grains that are large enough to be seen with the naked eye or a hand lens, like this granite.