DAJB+5.1

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=Vocabulary=


 * texture:** the look and feel of a rock


 * grains:** what gives a rock its texture.


 * igneous rock:** formed when magma hardens


 * sedimentary rock:** formed when remains of plants and animals are pressed together.


 * metamorphic rock:** formed when a rock is changed by pressure, heat or chemical reactions

=Outline=


 * ===How geologists classify rocks===
 * rocks form mountains, hills, beaches, and valleys
 * earths crust is made of rock
 * rocks are made of mixtures of minerals and other materials
 * geologists collect and study rocks in order to classify them
 * geologists observe the rock's color texture and determine its mineral composition.


 * ==Texture==
 * texture is very useful when trying to identify a rock
 * examples of different kinds of textures are: smooth, glassy, rough, or chalky
 * a rocks grain gives the rock its texture


 * ===grain size===
 * grains in rock are large and easy to see
 * other rocks there to small to be seen they only can be seen under a microscope


 * ===grain shape===
 * rocks vary in shape


 * ===grain pattern===
 * the grain in rock often form patterns
 * examples of patterns are: flat and wavy layers


 * ===no visible grain===
 * some rocks have no grain


 * ==mineral composition==
 * geologist must look closely at rock to determine its mineral composition
 * they cut the rock very thin so the light can shine through the crystal
 * some of the test they use is: testing the rocks surface with acid or testing with a magnet


 * ==origin==
 * there are three major groups of rocks: igneous rock, sedimentary rock, and metamorphic rock