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Vocabulary

 * Texture**: The look and feel of any rock's surface determined by the rock's size, shape, and pattern of a rock's grains.
 * Grains**:A particle of a type of mineral or other rock that gives a kind of rock its texture.
 * Igneous Rocks**: A type of rock that can form from cooling of hot, molten rock at or under the surface or top.
 * Sedimentary Rocks**: A type of rock that can form when pieces from other rocks or the leftovers or remains of plants or animals are pressed together with pressure and cemented together.
 * Metamorphic Rocks**: One type of rock that can form from a rock that is already there or existing that is changed by temperature, pressure, or some kinds of chemical reactions.

How Geologists Classofy Rocks

 * Rocks are very important building blocks for the earth and its moon.
 * Rocks on earth forms mountains and hills, valleys, beaches, and even the ocean floor
 * Earth's crust is made out of lots of types of rocks
 * Rocks are made of mixtures of minerals and other minerals, although sometimes, rocks may only contain one single type of mineral.
 * When studying any rock sample, all geologists observe the rock's color and the rock's texture and try to determine the mineral compostition of the rock.
 * Using all these characteristics of a rock, all geologists can calssify a rock.

Texture

 * With minerals, color by itself does not provide enough imformation to identify a type of rock.
 * The texture of a rock is very useful in trying to identify a type of rock.
 * To a geologist, a rock's texture is the look and feel of the rock's top or surface.
 * Some are smooth and glassy.
 * Some are rough and chalky.
 * Lots or most rocks are made of particles of other minerals or other rocks, which gives a rock its texture.
 * Grain Size
 * Lots of times, the grains in a rock are very big and easy to see or look at.
 * These rocks are called" coarse-grained"
 * Some other rocks, the grains can only be seen with a microscope.
 * These rocks are called " fine-grained".
 * Grain Shape
 * The grains in a rock vary widley in shape.
 * Some grains look like very litttle pieces of sand.
 * Some others might look like seeds or some kind of exoloding star.
 * In some rocks, like granite, the grain results from the shape of the crystals that form that rock.
 * In some other rocks, the grain shape results from fragments of other rocks.
 * Grain Pattern
 * The grains in a rock often form some kind of pattern.
 * Some rocks look like grains that looks like lots of rows of multicolored beads.
 * No Visible Grain
 * Some rocks have no grain, even when they are examined under any microscope.
 * These rocks have no grain because when they form from magma or something, they cool very quickly.

Mineral Composition

 * Lots of times, geologists have to look more closely at a rock than usual to determine its mineral composition.
 * By looking a a tiny silver of a rock under a microscope, a geologist can observe any rock's shape and size of crystals in the rock.
 * In identifying rocks, geologists also use some of the tests that are used to identify minerals.

Origin

 * There are threee major groups of rocks.
 * Igneous rock
 * It forms from the cooling of molten rock either using magma below the surface or lava at the surface or top.
 * Sedimentary Rock
 * It forms when particles of other kinds of rock or the remains of plants of amimals are pressed and cemented together
 * Sedimentary rocks forms in layers under or below the surface.
 * Metamorphic Rock
 * It is formed when a rock that is already existing or there is changed by temperature, pressure, or chemical reactions.
 * Most metamorphic rock forms very deep underground.

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