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In
geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes by which th ...

geology
, texture or
rock microstructure Rock microstructure includes the texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable b ...
refers to the relationship between the materials of which a
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
is composed. The broadest textural classes are crystalline (in which the components are intergrown and interlocking crystals), fragmental (in which there is an accumulation of fragments by some physical process),
aphanitic is aphanitic. Image:LvMS-Lvv.jpg, An aphanitic volcanic sand grain, with fine-grained groundmass, as seen under a petrographic microscope Aphanite, or aphanitic as an adjective (from the Greek language, Greek αφανης, "invisible"), is a name ...
(in which crystals are not visible to the unaided eye), and glassy (in which the particles are too small to be seen and amorphously arranged).Texture & Genesis of Rocks, Introductory Geology Laboratory, Christopher DiLeonardo, Ph.D., Marek Cichanski, Ph.D., Earth & Space Sciences,
De Anza College De Anza College is a public community college A community college is a type of educational institution An educational institution is a place where people of different ages gain an education, including preschools, childcare, primary-elementary s ...
The geometric aspects and relations amongst the component particles or crystals are referred to as the '' crystallographic texture'' or ''preferred orientation''. Textures can be quantified in many ways. The most common parameter is the crystal size distribution. This creates the physical appearance or character of a rock, such as grain size, shape, arrangement, and other properties, at both the visible and microscopic scale. Crystalline textures include
phaneritic Close-up of phaneritic granite exposed in Chennai, India A phanerite is an igneous rock whose Rock microstructure, microstructure is made up of crystals large enough to be distinguished with the unaided human eye, eye. (In contrast, the crystals ...
, foliated, and
porphyritic porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada (U.S.), Sierra Nevada, Rock Creek Canyon, California. Porphyritic is an adjective used in geology, specifical ...
. Phaneritic textures are where interlocking crystals of igneous rock are visible to the unaided eye. Foliated texture is where metamorphic rock is made of layers of materials. Porphyritic texture is one in which larger pieces (
phenocrysts image:montblanc granite phenocrysts.JPG, 300px, Granites often have large feldspar, feldspathic phenocrysts. This granite, from the Switzerland, Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that gi ...
) are embedded in a background mass made of much finer grains. Fragmental textures include
clastic of a clast (sand grain), derived from a basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ('' mafic '' lava) exposed at or very near the surface ...
, bioclastic, and
pyroclastic 300px, USGS scientist examines Mount_St._Helens.html"_;"title="pumice_blocks_at_the_edge_of_a_pyroclastic_flow_from_Mount_St._Helens">pumice_blocks_at_the_edge_of_a_pyroclastic_flow_from_Mount_St._Helens_ File:Volcanic_Stone_3D.ogg.html" ;"titl ...
. A preferred mineral orientation, is the texture of
metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism upright=1.35, Schematic representation of a metamorphic reaction. Abbreviat ...

metamorphic rock
in which its grains have a flattened shape (inequant), and their planes tend to be oriented in the same direction.Essentials of Geology, 3rd Ed, Stephen Marshak


See also

*
List of rock textures This page is intended to be a list of rock textural and morphological terms. A * Adcumulate * Agglomeritic * Adamantine a type of lustre * Amygdaloidal * Anhedral * Antitaxial veins * Aphanitic is aphanitic. Image:LvMS-Lvv.jpg, An a ...
*
Rock microstructure Rock microstructure includes the texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature. However, texture is still acceptable b ...
*
Texture (crystalline) In materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origins of ...
*
Igneous textures Igneous textures include the rock textures occurring in igneous rocks Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was o ...
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Vesicular texture left, A volcanic sand grain with many vesicles, viewed with a petrographic microscope. Scale box in millimeters. Vesicular texture is a volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth Earth is ...
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Amygdule Amygdules or amygdales form when the gas bubbles or vesicular texture, vesicles in volcanic lava (or other extrusive igneous rocks) are infilled with a secondary mineral such as calcite, quartz, Chlorite group, chlorite or one of the zeolites. Amy ...
*
Soil texture Soil texture is a classification Classification is a process related to categorization Categorization is the human ability and activity of recognizing shared features or similarities between the elements of the experience of the world (such as ...


References

Petrology {{petrology-stub