1. Different Types of Rocks
6th Grade

2. How do Rocks form?
Igneous Rocks: forms from the cooling of magma or lava
Sedimentary Rocks: forms when particles of other rocks or the remains of plants and animals are pressed and cemented together
Metamorphic Rocks: forms when an existing rock is changed by heat, pressure or chemical reactions

3. How can one classify rocks?
By its texture: the look and feel of the rock’s surface
Grains: particles of minerals or other rocks
Give a rock its texture

4. To describe a rock’s texture, geologists use terms based on the size, shape, and pattern of the grains

5. Grain Size
1) Fine Grain: grains are so small that they can only be seen with a microscope

6. Grain Size
- 2) Coarse grain: grains in a rock are large and easy to see

7. Grain Shape
Rounded Grain: (Conglomerate)
Jagged Grain: (Breccia)

8. Grain Pattern Non-banded: Banded: (foliated)
No patterns or bands noticeable
Banded: (foliated)
Grains lie in bands
of different colors

9. Igneous Rocks: “Igneous” comes from Latin word “ignis” which means “Fire”
1) Extrusive rock = igneous rock formed from lava that erupted onto Earth’s surface
2) Intrusive rock = igneous rock that is formed when magma is hardened beneath the Earth’s surface

10. Types of Igneous Rocks
Extrusive Rocks have a fine-grained or glassy texture
Intrusive Rocks have larger crystals in them because they cool more slowly

11. Sedimentary Rocks What is sediment?
Small, solid pieces of material that come from rocks or living things – ex. Sand grains, mud, pebbles AND shells, bones, leaves, stems, remains of living things

12. Sedimentary Rocks: formed from erosion, deposition, compaction, cementation
Erosion: running water, wind, or ice loosen and carry away fragments of rock.
Deposition: the process by which sediment settles out of the water or wind carrying it
Compaction: the process that presses sediments together
Cementation: the process in which dissolved minerals crystallize and glue particles of sediment together

13. Types of Sedimentary Rocks
Clastic Rock: a sedimentary rock formed when rock fragments are squeezed together
Organic Rock: a sedimentary rock formed when the remains of plants and animals are deposited in thick layers

14. Metamorphic Rocks: “meta” = change and “morphosis” = form
Rocks that are changed by heat and pressure deep beneath the Earth’s surface
Metamorphic rocks can form out of igneous, sedimentary, or other metamorphic rock
Collisions between Earth’s plates can push the rock down toward the heat of the mantle

15. Metamorphic Rocks
Foliated: have their grains arranged in parallel layers or bands
Nonfoliated: mineral grains in these rocks are arranged randomly

16. Granite turns into Gneiss
Shale turns into Slate
Limestone turns into Marble