Unit: Rocks and Minerals General Task How Are Rocks Identified?

The following instructional plan is part of a GaDOE collection of Unit Frameworks, Performance Tasks, examples of Student Work, and Teacher Commentary. Many more GaDOE approved instructional plans are available by using the Search Standards feature located on GeorgiaStandards.Org. Unit: Rocks and Minerals General Task How Are Rocks Identified? Standards (Content and Characteristics): S6E5. Students will investigate the scientific view of how the earth s surface is formed. b. Investigate the contribution of minerals to rock composition. c. Classify rocks by their process of formation. d. Describe processes that change rocks and the surface of the earth. S6CS1. Students will explore the importance of curiosity, honesty, openness, and skepticism in science and will exhibit these traits in their own efforts to understand how the world works. a. Understand the importance of and keep honest, clear, and accurate records in science. S6CS6. Students will communicate scientific ideas and activities clearly. c. Organize scientific information using appropriate tables, charts, and graphs, and identify relationships they reveal. S6CS2. Students will use standard safety practices for all classroom laboratory and field investigations. a. Follow correct procedures for use of scientific apparatus. b. Demonstrate appropriate techniques in all laboratory situations. c. Follow correct protocol for identifying and reporting safety problems and violations Enduring Understanding: Rocks are classified based on how they formed and their mineral composition. Sedimentary rocks are formed by the ongoing deposition of rocks and other sediments that are cemented together. Rocks at the surface of the Earth weather, forming sediments that are buried, then compacted, heated, and often re-crystallize into new rock. July 26, 2007 Page 1 of 10

Essential Questions: One Stop Shop For Educators How are rocks formed? How are rocks classified? Pre-Assessment: ADMINISTRATION PROCEDURES Put rocks at various stations. Ask students to identify the rocks. Provide students with a blank answer document to record responses. Students will move from station to station and identify as many rocks as possible using visual observations. Outcome / Performance Expectations: General Teacher Instructions: Materials Needed: Students will be able to identify common igneous, sedimentary, and metamorphic rocks. Students will interpret the process of formation of rocks by looking at their textures. Obtain mineral and rock specimens from scientific supply house, from gem and mineral show, or by collecting them. Local mineral societies may also have materials which they can donate. Rocks that the students will identify might include the following as examples of IGNEOUS ROCKS: o Granite o Gabbro o Diorite o Basalt o Rhyolite o Andesite o Pumice o Scoria o Obsidian SEDIMENTARY ROCKS: o Sandstone o Limestone o Rock gypsum o Shale o Conglomerate o Breccia July 26, 2007 Page 2 of 10

Safety Precautions: Task with Student Directions: METAMORPHIC ROCKS: o Slate o Mica schist o Gneiss o Marble o Quartzite Students should wear safety goggles. Students should wash hands at the conclusion of the activity. Background information on Rocks A rock is an aggregate of one or more minerals There are three basic categories of rocks: Igneous (or cooled from hot molten lava or magma) - ex. granite, basalt Sedimentary (or fragments laid down by water or wind) - ex. sandstone, shale, limestone Metamorphic (or rocks changed by heat and or pressure) - ex. gneiss, schist, slate, marble Rocks are the building blocks of the Earth's crust. We can identify the minerals present in rocks. We can learn about the process of formation of rocks by looking at their textures (or grain sizes, shapes, and arrangement). I. IGNEOUS ROCKS Igneous rocks are "fire-formed". They crystallized from hot, molten lava or magma as it cooled. Magma is hot, molten rock beneath the surface of the Earth. Lava is hot, molten rock which has flowed out onto the surface of the Earth. Magma may cool within the Earth's crust to form igneous rocks. But lava cools much more quickly because it is on the Earth's surface where temperatures are much lower than they are deep within the Earth. Cooling rates influence the texture of the igneous rock: Quick cooling = fine grains Slow cooling = coarse grains July 26, 2007 Page 3 of 10

Igneous rocks are classified (or named) based on their composition (which minerals they contain) and texture (or the size of the mineral grains). The texture is a result of the process of formation of the igneous rocks. A variety of textures are present in igneous rocks. For this exercise, we will only consider a few textures (and their process of formation): Fine-grained (produced by quick cooling and crystallization of lava), Coarse-grained (produced by slow cooling and crystallization of lava), Glassy (produced by instantaneous cooling of lava so fast that there is no time for minerals to crystallize), and Vesicular (contains holes made by gas bubbles in a quick-cooling or instantaneous-cooling lava). Now and then, you may see an igneous rock with a mixture of grain sizes larger minerals surrounded by smaller minerals. This indicates a complicated process of formation of the igneous rock, in which the magma initially cooled very slowly, and then the magma erupted as lava and cooled quickly. An igneous rock with mixed grain size indicates a mixed cooling history. Part A. Examining the minerals in coarse-grained igneous rocks. Examine granite, diorite and gabbro with the magnifying glass or microscope. Describe the appearance of at least two minerals you can see in each rock. Igneous Rock Granite Describe two physical properties of the rock Diorite Gabbro Part B. Examining the minerals and textures of igneous rocks Examine the igneous rocks listed in the table below. Tell whether their minerals are visible and readily seen with the naked eye (coarse grained), or July 26, 2007 Page 4 of 10

whether they are too small to identify (fine grained), or whether the texture is glassy, vesicular (bubbles) or mixed. Then interpret the process of formation of the igneous rock. Igneous Rock Obsidian Pumice Scoria Granite Rhyolite Diorite Andesite Basalt Gabbro Texture (fine-grained, coarsegrained, glassy, vesicular, or mixed) Process of formation (fast cooling, slow cooling, instantaneous cooling, gas bubbles released during cooling, or mixed cooling history) II. SEDIMENTARY ROCKS Sedimentary rocks are made from sediment. Sediment is loose particulate material (clay, sand, gravel, shells, plant fragments, etc.). Sediment may be transported and deposited by moving water, wind, or ice. Sediment becomes compacted and cemented to form sedimentary rock. We can interpret the process of formation of sedimentary rocks by looking at their grain size and shape (i.e., their texture). Fine-grained sedimentary rocks were deposited by still, quiet, low-energy water. Coarse-grained sedimentary rocks were deposited by rapidly-moving, high-energy water. We can also look at the shapes of the grains in sedimentary rocks to learn about their process of formation. Rounded grains in a sedimentary rock July 26, 2007 Page 5 of 10

indicate a long distance of transportation during which the grains of sediment rolled and tumbled along, which wore down any sharp corners. Angular grains in a sedimentary rock indicate a short distance of transportation. Part A. Examining the minerals in sedimentary rocks. Examine the sedimentary rocks listed in the table below. Use a magnifying glass. Describe physical characteristics of each in the table below. Answer the questions below. Sedimentary rock Sandstone Describe two physical properties of the rock Limestone Rock gypsum Shale Part B. Examining the textures of sedimentary rocks Examine the sedimentary rocks listed in the table below. Use a magnifying glass. Describe the grain size and then interpret the process of formation, indicating whether it was deposited by high-energy or low-energy water. Then in the next table, examine the differences in grain shape in conglomerate and breccia, and interpret the process of formation in terms of distance of transport. Sedimentary rock Conglomerate Sandstone Shale Breccia Grain size (fine-grained or coarse-grained) Process of formation (deposition by high-energy or lowenergy water) July 26, 2007 Page 6 of 10

Sedimentary rock Conglomerate Breccia Grain shape (angular or rounded) Process of formation (long or short distance of transport) III. METAMORPHIC ROCKS Metamorphic rocks formed as a result of changes to other types of rocks. The processes of formation of metamorphic rocks involve changes caused by heat and pressure associated with deep burial and tectonic pressures (caused by moving tectonic plates). Those changes, called metamorphism, include compaction (which makes the rock become more dense and makes the grains move closer together), and recrystallization (the growth of new minerals). In other words, metamorphism causes changes in the texture and minerals of rocks. As shale is subjected to increasing heat and pressures, the clay minerals in it are recrystallized to form micas (such as muscovite and biotite). As heat and pressure increase, the mica grains increase in size. Pressure causes the minerals in a metamorphic rock to become oriented perpendicular to the direction of force. The mica grains (such as muscovite and biotite) become aligned parallel with one another to form a new texture called foliation. Rocks with foliation include slate, schist and gneiss. Metamorphic rocks which lack mica minerals are called non-foliated, and they have an even, granular texture with no aligned minerals. Non-foliated metamorphic rocks include marble and quartzite. Part A. Examining minerals in metamorphic rocks. Examine the metamorphic rocks listed in the table below. Use a magnifying glass. Describe the physical properties of each in the table below. July 26, 2007 Page 7 of 10

Metamorphic rock Physical characteristics Slate Schist Gneiss Marble Quartzite Part B. Examining textures in metamorphic rocks. Examine the metamorphic rocks listed in the table below. Use a magnifying glass. Look at the textures to determine if the rocks are foliated or non-foliated. Metamorphic rock Texture (foliated or non-foliated) Gneiss Marble Schist Quartzite Slate Resources: http://www.minsocam.org/msa/k12/k_12.html http://volcano.und.nodak.edu/vwdocs/vwlessons/rocks.html http://gpc.edu/~pgore/earth&space/gps/minerals.html http://gpc.edu/~pgore/geology/physical_lab/mineral-handy-dandy.htm http://gpc.edu/~pgore/geology/physical_lab/mineral-fill-in-sheet.htm http://mineral.galleries.com/minerals/physical.htm#phy http://www.classzone.com/books/earth_science/terc/content/visualizations/e s0505/es0505page01.cfm?chapter_no=visualization http://www.mii.org/ July 26, 2007 Page 8 of 10

Homework / Extension: Instructional Task Accommodations for ELL Students: Instructional Task Accommodations for Students with Specific Disabilities: Instructional Task Accommodations for Gifted The Georgia Mineral Society provides mini-grants for teachers to assist with the purchase of rocks and minerals. See http://www.gamineral.org/minigrant.htm The Georgia Mineral Society has a list of retired hobbyist and working professionals who have agreed to give talks on subjects related to our hobby. Interested parties may contact GMS at gmsmail@gamineral.org and request a speaker. GMS speakers will review and fulfill these requests as their individual schedules permit! Learn more about our GMS Speakers Bureau by following this link: http://www.gamineral.org/speakersbureau.html Plan a fieldtrip to a local museum that has displays of minerals and rocks, such as the Weinmann Mineral Museum (TELLUS) in Cartersville. Identify and locate information on your home state's (or a nearby state's) state mineral. You can learn about the state mineral, state gem, and state fossil on this web page. See also http://www.cviog.uga.edu/projects/gainfo/mineralresn.htm Work with a student with strong English language skills Highlight key points in the article Reduce the number of key points these students are responsible for knowing Extend the time to complete the task Seat student near teacher or positive role model during direct instruction and student centered activity time Adjust teacher talk to increase comprehensibility during direct instruction and while conveying task directions Speak carefully and avoid slang terms or unfamiliar idiomatic experience Describe the characteristics of the rocks for visually impaired students Break work into manageable parts Reinforce oral instructions with written instructions Graphically display an analysis of the expected task including a checklist to facilitate attention to task and organizational skills Assess informally on an on-going basis Use alternative assessments Have gifted students use rock identification keys from the web or from a book to identify minerals and rocks. Give them unlabeled rocks to identify. Students use common mineral testing techniques to identify the actual July 26, 2007 Page 9 of 10

Students: mineral composition of the rocks used as examples. Provide digital microscopes to examine the rocks. Have the gifted students take digital images of the rocks and prepare a computer presentation for the class indicating how each of the rocks formed. Allow role plays and scenarios. Offer choices and chunk concepts for students. Problem-based Learning Activities. July 26, 2007 Page 10 of 10