5.1 Classifying rocks


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.
5.Metamorphic rock- A type of rock that forms from an existing rock that is changed by heat,pressure or chemical reactions


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.


  • 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.

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