2. Mineral vs. Rock A rock is a solid combination of minerals or mineral materials. Minerals are inorganic, meaning that living things did not produce them and they occur naturally. Geologists don’t classify coal as a mineral because coal was created from plant remains. Materials like brick and concrete are not considered minerals either. Minerals are the building blocks of rocks

3. Mineral vs. Rock Granite is made up of quartz, feldspar, mica, and hornblende. A magnified view reveals the individual crystals of the minerals that make up granite. Quartz Hornblende Mica Feldspar

4. Types of Rocks Rocks are classified into three major groups— igneous, sedimentary, and metamorphic—based on how they form.

5. Classifying Rocks The size, shape, and arrangement of the crystals and other particles that make up a rock give the rock its texture. A rock’s texture reveals what the rock is made from and how and where it formed.

6. Igneous Rocks Igneous rock forms when molten material cools and solidifies either inside Earth or at the surface.

7. Igneous An igneous rock is a rock that forms from magma. Magma is a mixture of molten rock and gases, including water vapor, which forms underground. Magma that flows out of volcanoes is called lava.

8. Igneous An igneous rock that forms underground from hardened magma is called an intrusive rock. Intrusive rocks = cool slowly underground = large crystals = coarse texture. An igneous rock that forms at Earth’s surface is called an extrusive rock. Extrusive igneous rocks = cool very quickly at the surface = small crystals = fine-grained texture.

9. Igneous Basalt is a fine- grained, extrusive rock. As this basalt cooled, the rock formed into hexagonal columns.

10. Igneous An igneous rock’s color gives a clue to its mineral composition. Ex: Gabbro, an intrusive rock, and basalt, an extrusive rock formed from magma rich in iron and magnesium. The rocks are dark and dense. Ex: Granite is a coarse-grained, intrusive rock with a high silica content. Granite is less dense and lighter in color than basalt and gabbro.

11. Sedimentary Rocks A sedimentary rock is a rock that forms over time as sediment is squeezed and cemented together. Geologists classify sedimentary rocks into three main groups according to how they form: clastic rocks, chemical rocks, and organic rocks.

12. Sedimentary Sediment consists of small, solid pieces of material that comes from rocks or living organisms. The process of weathering breaks down rock at Earth’s surface, turning it into smaller pieces. Minerals dissolved in water are also sediment.

13. Sedimentary Sediment is often carried away by running water or wind to a new location, where it is deposited in layers. As sediment piles up, the pressure causes the deeper sediment to be compressed. Dissolved minerals in the water seep into the space between particles of sediment and form a kind of cement.

14. Sedimentary Colorful layers of sandstone, like those in this Utah canyon, formed over millions of years as water and wind laid down sediment.

15. Sedimentary Clastic Rock Sedimentary rocks that form from the broken fragments of other rocks are called clastic rocks. The fragments that make up clastic rocks are usually held together by cement.

16. Sedimentary Clastic rocks are classified mainly based upon the average size of the fragments that they contain. EXAMPLES: Conglomerate is made of gravel and pebbles. Breccia is made up of sharp-edged fragments. Sandstone is formed from grains of sand. Mudstone is made primarily of mud or silt. Shale is mudstone made of flat grains aligned so that the rock can split into sheets.

17. Sedimentary Conglomerate is a sedimentary rock in which rounded pieces of other rocks are cemented together.

18. Sedimentary Chemical Rock Chemical sedimentary rocks form when minerals precipitate out of solution. Rainwater dissolves many minerals on the land. These dissolved minerals are then carried into the ocean. As water evaporates from the ocean surface, the concentration increases until the minerals precipitate.

19. Sedimentary The strangely shaped rocks in Mono Lake, California, are made of tufa, a chemical rock composed of calcium carbonate.

20. Sedimentary Organic Rock Some rocks form as the result of organic processes. Marine animals extract calcium carbonate from ocean water to form their shells and skeletons. The shells and skeletons sink to the ocean floor. The fragments compact and cement together, forming limestone.

21. Sedimentary The cliffs of Dover on the southern coast of England are composed of chalk, a type of fine-grained organic limestone.

22. Metamorphic Rock Metamorphic rock is rock that has been changed by temperature, pressure, or reactions with hot water. Most metamorphic rocks form under high temperatures and pressures deep underground.

23. Metamorphic Metamorphism can result in a rock with a mineral content that is different from that of the original rock. Heat deep inside Earth allows the minerals to recrystallize, and small crystals to enlarge. Chemical changes occur, and new minerals may replace the original minerals. ShaleSlateSchistGneiss

24. Rock Cycle The rock cycle is a series of processes in which rocks continuously change from one type to another.

25. Rock Cycle Constructive forces form new igneous rock. Destructive forces break down rock, forming sediment. Other forces push rock deep beneath the surface, where heat and pressure form metamorphic rock.

26. Rock Cycle Depending on their pathway through the cycle, rocks can wear away, undergo metamorphi sm, or melt and form new igneous rock. Compacting & Cementation Melting Heat & Pressure Weathering & Erosion CoolingMelting Weathering & Erosion Heat & Pressure