**ESAY+5.1**

=5.1 Classifying rocks=

Vocabulary
5.**Metamorphic rock-** A type of rock that forms from an existing rock that is changed by heat,pressure or chemical reactions
 * 1.Grains**:-A particle of mineral or other rock that gives a rock a texture
 * 2.Texture**:-The look and fell a rock's surface determined by the size ,shape,and a pattern of a rock grains
 * 3.Igneous rock**:-A type of rock that forms from the cooling of molten rock at or below the surface.
 * 4.Sedimentary rock**:-A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.

Outline

 * How Geologists classify rocks**


 * On Earth**,** rocks forms mountains, hills, valleys, beaches even the ocean floor.
 * Earth's crust is made of rock.
 * Geologists collect and study samples of rock in order to classify them.
 * When studying a rock sample, geologist observe rocks color and texture and determine its mineral composition.


 * Texture**


 * A rocks texture is very useful in identifying the rock.
 * Some rocks are smooth and glassy.To describe a rock's texture, geologists use a number of terms based on the size and pattern of the rock's grains.


 * Mineral Composition**


 * Often geoligist must look more closely at a rock to determine its mineral composition.
 * To prepare a rock for viewing under the microscope, geologist cut the rock very thin, so that light can shine through its crystals.
 * origin**


 * There are three major groups of rocks:igneous rock,sedimentary rock, and metamorphic rock.
 * Rocks belonging to each of thesedifferent forms in different way.