Rock (geology)

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Rock (geology)

In geology

Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
, rock is a naturally occurring solid aggregate of mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s and/or mineraloid

Mineraloid

A mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals....
s.

The Earth's outer solid layer, the lithosphere

Lithosphere

File:Plates tect2 en.svgFile:Earth-crust-cutaway-english.svgThe lithosphere is the rigid outermost shell of a rocky planet....
, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic

Metamorphic rock

Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form"....
. The scientific study of rocks is called petrology

Petrology

In geology, petrology is the study of Rock s, and the conditions in which they form. Lithology once was approximately synonymous with petrography, but in current usage, lithology is a subdivision of petrology focusing on macroscopic hand-sample or outcrop-scale description of rocks, while petrography is the speciality that deals with m...
, and petrology is an essential component of geology.

Rocks are classified by mineral and chemical composition, by the texture

Texture (geology)

Texture in geology refers to the physical appearance or character of a rock, such as grain size, shape, arrangement, and pattern at both the megascopic or microscopic surface feature level....
of the constituent particles and by the processes that formed them.

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Rock classification

Rocks are classified by mineral and chemical composition, by the texture

Texture (geology)

Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
, sedimentary

Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
and metamorphic

Metamorphic rock

Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form"....
. They are further classified according to particle size

Particle size (grain size)

Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithification particles in clastic rocks....
. The transformation of one rock type to another is described by the geological model called the rock cycle

Rock cycle

The rock cycle is a fundamental concept in geology that describes the dynamic transitions through geologic time among the three main rock types: sedimentary, metamorphic rock, and igneous....
.