Rock Identification Lab, 60 Points This is a BIG lab! Work carefully and thoroughly Name: Date: Period: Lab Skills and Objectives 1. You will examine, classify, and identify several samples of igneous, sedimentary and metamorphic rocks. 2. You will compare and contrast characteristics of these three types of rocks. Materials Igneous, sedimentary, and metamorphic rock samples Hand lens Sandpaper Earth Science textbook, Chapter 6 Procedure: Part A, Igneous Rocks Rock samples: basalt, gabbro, granite, obsidian, pumice, rhyolite, and scoria. 1. Sort the igneous rock samples by color into two groups: Light-colored (felsic) and dark-colored (mafic). 2. Sort the rocks in each color group into the following three texture groups: coarse-grained rocks (composed of crystals large enough to be seen with the unaided eye); fine-grained rocks (composed of mineral crystals that are too small to be seen with the unaided eye); and rocks with glassy texture containing no crystals. NOTE: rocks with porous texture (lots of holes) are also considered glassy. 3. Write the name of each igneous rock listed above in the correct location on the chart below. Refer to the Summary: Igneous Rocks table on page 124 of the textbook as needed. 4. Place each rock on the appropriate box on the chart below. One box will have two rock types. Have your teacher check for correctness before moving on. Igneous Rock Chart (7 points) Texture Light-colored (felsic) rocks Dark-colored (mafic) rocks Glassy Fine-grained Coarse-grained
Analysis and Conclusions: Igneous Rocks 1. (1 point) Using a hand lens, look carefully at the mineral grains in the sample of granite. What minerals occur in granite? 2. (2 points) What minerals would you expect to occur in rhyolite? Explain. 3. (2 points) What minerals can you identify in the sample of gabbro? Explain. 4. (2 points) What minerals would you expect to find in basalt? Explain. 5. (1 point) Based only on its color and texture, where would you place obsidian on the chart? 6. (1 point) Based on the information in the Summary: Igneous Rocks table in your textbook, where would you place obsidian on the chart? 7. (1 point) Explain why your second classification of obsidian in the correct answer. 8. (2 points) Examine and compare the pumice and scoria. Why are the holes in the scoria larger than the holes in the pumice? Hint: Gas bubbles can move more easily in thin lava than in thick lava. Procedure: Part B, Sedimentary Rocks Rock samples: coal, conglomerate, dolomite limestone, rock salt, sandstone, shale, and shell limestone. 1. Read and refer back to pages 127-131 of your text. 2. Write the name of each sedimentary rock listed above in the correct location in the Sedimentary Rock Chart. 3. Carefully examine the set of sedimentary rock samples. Place each rock on the appropriate box on the chart below that matches its description. Have your teacher check for correctness before moving on.
Sedimentary Rock Chart (7 points) Clastic rocks Chemical rocks Organic rocks Sand and gravel cemented together, looks like concrete Tiny grains of calcite, gray or tan in color, dense Rock made from plant remains, black and sooty Cemented sand grains (usually quartz), gritty feel Natural from of salt, clear or white in color Skeletons and shells of sea animals; grayish Compact mud, earthy odor, usually easily broken Analysis and Conclusions: Sedimentary Rocks 9. (1 point) How are the particles that make up the conglomerate different from the particles in the sandstone or in the shale? 10. (1 point) Look carefully at the largest grains in the conglomerate sample. Of what mineral are they composed? 11. (1 point) Using a hand lens examine a piece of sandpaper and the sandstone sample. Why does the sandstone feel like sandpaper? 12. (1 point) Of what mineral or minerals is the sandstone made? 13. (2 points) In what way is the overall appearance of the shale different from the conglomerate and the sandstone? 14. (2 points) What chemical test could be used to identify both of the limestones you examined? Explain. 15. (1 point) How do the two limestone samples differ in appearance?
16. (1 point) Examine the particles that make up the shell limestone. Are they whole or in fragments? 17. (1 point) Name any particles in the shell limestone that you can recognize. 18. (1 point) Is rock salt different from the mineral halite? Explain. 19. (2 points) What is the overall color and texture of the coal? 20. (2 points) Why are fossils rare in conglomerates? Hint: think about how and where conglomerates form and what that process would do to animal or plant remains. Procedure: Part C, Metamorphic Rocks Rock samples: gneiss, marble, quartzite, schist, and slate. 1. In general, metamorphic rocks can be placed into one of two texture categories, foliated and nonfoliated. Foliated (showing bands of minerals) metamorphic rocks have a layered appearance. Nonfoliated metamorphic rocks have no apparent layering. Carefully examine the set of metamorphic rock samples and separate those that appear foliated from those that appear nonfoliated. Note: This foliation can sometimes be very subtle. 2. Read and refer back to pages 134-137 of your text. 3. Write the name of each metamorphic rock in the correct location on the Metamorphic Rock Chart. 4. Carefully examine the set of metamorphic rock samples. Place each rock on the appropriate box on the chart below that matches its description. Have your teacher check for correctness before moving on. Foliated Metamorphic Rock Chart (5 points) Nonfoliated Coarse grains, light and dark bands Hard, dense, crystalline, fused quartz grains Thin and parallel bands with wavy, uneven surfaces Crystalline, visible crystals of calcite, often white or gray Red, gray, green, blue, or purple, very fine grained, splits into smooth, flat layers
Analysis and Conclusions: Metamorphic Rocks 21. (2 points) Many gneisses are believed to have formed from granites. Compare the minerals that occur in gneiss with those that occur in granite and list them. (You may need to check out Chapter 5 for pictures). 22. (1 point) How is gneiss different in appearance from granite? 23. (1 point) Look at the sample of schist. How do the color and thickness of its mineral bands compare with those in the sample of gneiss? 24. (2 points) Mica schist is the most common kind of schist. In it, flakes of mica are all parallel and easily seen. Is your sample mica schist? Why or why not? 25. (1 point) Which sedimentary rock does slate most closely resemble? 26. (1 point) How is the texture of marble different from the texture of quartzite? 27. (1 point) How could a mineral hardness test be used to tell quartzite from marble? 28. (1 point) How could an acid test be used to tell quartzite from marble? 29. (3 points) Not including marble and quartzite, what general properties of appearance can be used to determine whether a rock is metamorphic, igneous or sedimentary? In other words, what visible properties set apart these three main rock types? What would you look for to tell the difference?