1. Rocks Classifying Rocks

2. Rock Study When studying a rock sample, geoliogists observe the rock’s mineral composition, color, and texture.

3. Mineral Composition Rocks are made of mixtures of minerals and other materials. 20 minerals make up most of the Earth’s surface. We call these minerals rock-forming minerals.

4. Mineral Color A rock’s color provides clues to the rock’s mineral composition. Usually lighter the color rock, the more silica present. The darker, less. Geologists observe the shape and color of crystals in a rock to identify the minerals that the rock contains. Acid is put on rocks to see the presence of carbonates in the rock.

5. Texture Most rocks are made up of particles of minerals called grains. The grains affect the texture of the rock. The size, shape, and pattern of the grains determine how smooth or rough the rock becomes.

6. Grain Size Large grained rocks are referred to as coarse-grained. Small grained rocks are referred to as fine grain. Some rocks have no visible grains.

7. Grain Shape Rounded grain Jagged grain

8. Grained Pattern Non Banded Banded

9. How rocks form? You can classify rocks by its origin. A rock’s origin is how the rock formed. Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock.

10. 3 Types of Rock Igneous Rock Sedimentary Rock Metamorphic Rock

11. Igneous Rock Forms when magma or lava cools and hardens.

12. Sedimentary Rock Forms when pieces of rock are pressed and cemented together.

13. Metamorphic Rock Forms from other rocks that are changed by heat and pressure.