Lab: ROCK IDENTIFICATION

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1 Name: Date: Lab: ROCK IDENTIFICATION Background: As you observed in the previous investigation, minerals are the building blocks that form rocks. Rocks are classified as igneous, sedimentary, or metamorphic based on the how there were formed. Be sure to check the Rock Cycle found on page 6 of your ESRT. Igneous rocks are formed from the solidification of liquid lava or magma. Magma that is cooled slowly forms mineral crystals in the rock that can be seen and identified. Lava that is cooled fast as it comes out on the surface of the earth forms very small (unnoticeable) crystals or if cooled very fast will turn to glass. Sometimes gasses will make tiny pockets within the rock giving the rock a vesicular texture. Sedimentary rocks are rocks that are formed through the process of deposition of sediment. Sediment can be as big as boulders or as small as clay; it can be organic like seashells or carried in solution like dissolved salt. Sediment that is carried along in a river and makes its way to be dumped into the sea is said to be deposited and is on its way to becoming a sedimentary rock. Often sedimentary rocks contain fossils and you can see the layers of sediment that settled in the water. Sometimes sediment is deposited as the water evaporates away leaving the once dissolved materials behind. These sediments are formed chemically. If a sedimentary rock is only made up of sediments that once came from living things they are called organic sedimentary rocks. Some chemically or organically formed sedimentary rocks are made of only one mineral and are therefore called mono-mineralic rocks. Metamorphic rocks are rocks that have been changed by heart and pressure but have not been melted. Metamorphic rocks are divided in to two main groups, foliated (mineral banded) and not-foliated (no mineral bands). Foliated rocks are easy to identify. Simply look for rocks that have different minerals that seem to line up into parallel layers or bands. The non-foliated metamorphic rocks are a bit harder to identify. These rocks are often recrystallized mono-mineralic rocks, which will not form mineral bands, due to the fact that the rocks are only made from one mineral. 1. Which rock is formed from deposition of sediments? 2. Which rock is formed from heat and pressure? 3. Which rock is formed from the solidification of magma?

2 IGNEOUS ROCKS Objective: You will determine the name of unknown igneous rocks based on their physical characteristics using your ESRT. Materials: Unknown igneous rocks, ESRT Directions: For each unknown igneous rock, identify the key physical characteristics. Using your ESRT, determine the name of the igneous rock based on the observed characteristics. Sample A Characteristic Color Light Colored Dark Colored Felsic/Mafic Felsic Mafic Density Low Density High Density Texture Coarse Grained Fine Grained Glassy Vesicular Cooling Rate Fast Slow In a COMPLETE SENTENCE, state why this rock would be classified as an igneous rock. Sample B Characteristic Color Light Colored Dark Colored Felsic/Mafic Felsic Mafic Density Low Density High Density Texture Coarse Grained Fine Grained Glassy Vesicular Cooling Rate Fast Slow In a COMPLETE SENTENCE, state why this rock would be classified as an igneous rock.

3 Sample C Characteristic Color Light Colored Dark Colored Felsic/Mafic Felsic Mafic Density Low Density High Density Texture Coarse Grained Fine Grained Glassy Vesicular Cooling Rate Fast Slow In a COMPLETE SENTENCE, state why this rock would be classified as an igneous rock. Sample D Characteristic Color Light Colored Dark Colored Felsic/Mafic Felsic Mafic Density Low Density High Density Texture Coarse Grained Fine Grained Glassy Vesicular Cooling Rate Fast Slow In a COMPLETE SENTENCE, state why this rock would be classified as an igneous rock.

4 Questions 1. What is an igneous rock? 2. Define and explain the difference between magma and lava? 3. Where do intrusive igneous rocks form? 4. Where do extrusive igneous rocks form? 5. Describe the size of the mineral crystals you would expect to see in extrusive rocks and intrusive rocks. 6. What factors determine the crystal size in an igneous rock? 7. Why does molten rock material cool more slowly underground? 8. How can two different igneous rocks have the same mineral composition? 9. What does a vesicular igneous rock have? 10. What features do you look for to identify an igneous rock?

5 SEDIMENTARY ROCKS Objective: You will determine the name of unknown sedimentary rocks based on their physical characteristics using your ESRT. Materials: Unknown Sedimentary rocks, ESRT Directions: For each unknown sedimentary rock, identify the key physical characteristics. Using your ESRT, determine the name of the igneous rock based on the observed characteristics. Sample A Key Identifying Features Question Clasts Can you see clasts in this sample? If yes, are the clasts all the same size? If yes, are the clasts angular or rounded? Angular Rounded If yes, what size are the clasts? Sand Silt Clay Mixed Strata Fossils Shells Can you clearly see defined layers in this sample? Can you see fossils in the sample? Are shells cemented together? If yes, will the rock effervesce with HCl acid? In a COMPLETE SENTENCE, state why this rock would be classified as a sedimentary rock.

6 Sample B Key Identifying Features Question Clasts Can you see clasts in this sample? If yes, are the clasts all the same size? If yes, are the clasts angular or rounded? If yes, what size are the clasts? Sand Silt Clay Mixed Strata Fossils Shells Can you clearly see defined layers in this sample? Can you see fossils in the sample? Are shells cemented together? If yes, will the rock effervesce with HCl acid? In a COMPLETE SENTENCE, state why this rock would be classified as a sedimentary rock.

7 Sample C Key Identifying Features Question Clasts Can you see clasts in this sample? If yes, are the clasts all the same size? If yes, are the clasts angular or rounded? If yes, what size are the clasts? Sand Silt Clay Mixed Strata Fossils Shells Can you clearly see defined layers in this sample? Can you see fossils in the sample? Are shells cemented together? If yes, will the rock effervesce with HCl acid? In a COMPLETE SENTENCE, state why this rock would be classified as a sedimentary rock.

8 Sample D Key Identifying Features Question Clasts Can you see clasts in this sample? If yes, are the clasts all the same size? If yes, are the clasts angular or rounded? If yes, what size are the clasts? Sand Silt Clay Mixed Strata Fossils Shells Can you clearly see defined layers in this sample? Can you see fossils in the sample? Are shells cemented together? If yes, will the rock effervesce with HCl acid? In a COMPLETE SENTENCE, state why this rock would be classified as a sedimentary rock.

9 Questions: 1. Describe the process of the formation of a clastic sedimentary rock. 2. Define: compaction and cementation. 3. Why do clastic sedimentary rocks generally form underwater? 4. What sedimentary rock would form farthest from a shoreline? 5. A clastic sedimentary rock is identified based on its. 6. What are often found in sedimentary rocks and not in either igneous or metamorphic rocks? 7. What features do you look for to identify a sedimentary rock?

10 METAMORPHIC ROCKS Objective: You will determine the name of unknown igneous rocks based on their physical characteristics using your ESRT. Materials: Unknown igneous rocks, ESRT Directions: For each unknown igneous rock, identify the key physical characteristics. Using your ESRT, determine the name of the igneous rock based on the observed characteristics. Sample A Key Identifying Features Is this metamorphic rock foliated? If yes, is banded or mineral alignment? Banded Mineral alignment Is this metamorphic rock non-foliated? If yes, does it react with acid? If, does it scratch glass? Are there any key metamorphic identifier minerals? Garnet Mica In a COMPLETE SENTENCE, state why this rock would be classified as a metamorphic rock.

11 Sample B Key Identifying Features Is this metamorphic rock foliated? If yes, is banded or mineral alignment? Banded Mineral alignment Is this metamorphic rock non-foliated? If yes, does it react with acid? If, does it scratch glass? Are there any key metamorphic identifier minerals? Garnet Mica In a COMPLETE SENTENCE, state why this rock would be classified as a metamorphic rock.

12 Sample C Key Identifying Features Is this metamorphic rock foliated? If yes, is banded or mineral alignment? Banded Mineral alignment Is this metamorphic rock non-foliated? If yes, does it react with acid? If, does it scratch glass? Are there any key metamorphic identifier minerals? Garnet Mica In a COMPLETE SENTENCE, state why this rock would be classified as a metamorphic rock.

13 Sample D Key Identifying Features Is this metamorphic rock foliated? If yes, is banded or mineral alignment? Banded Mineral alignment Is this metamorphic rock non-foliated? If yes, does it react with acid? If, does it scratch glass? Are there any key metamorphic identifier minerals? Garnet Mica In a COMPLETE SENTENCE, state why this rock would be classified as a metamorphic rock.

14 Questions: 1. What two conditions are necessary for the formation of a metamorphic rock? 2. What is the difference between regional and contact metamorphism/ 3. Which metamorphic rock forms from sandstone? From limestone? From bituminous coal? 4. Which is the rock formed only from contact metamorphism? 5. From where does metaconglomerate get it s name? 6. Using the top portion of the Scheme for Metamorphic Rock Identification, list the steps involved in turning slate into gneiss (name the rocks in order). 7. List the minerals in slate. 8. If heat and pressure is added to shale, what will be the new rock? 9. What is marble composed of? What test can you perform on marble to check that it is marble. 10. What features do you look for to identify an metamorphic rock? a. b.