Geo Lab #6 Rocks and Minerals

Name: _____________________________________ Section: _______ Laboratory 7: Rocks and Minerals Description: This lab gives you an opportunity to examine common rocks and minerals found throughout the world. Minerals are inorganic substances with specific chemical compositions and crystalline structures. Different minerals have different properties, such as color, shape, density and degree of resistance to weathering. Rocks are aggregates of minerals; they share many of the properties of the minerals that comprise them, but also have properties that derive from the manner in which they were formed. Rocks can be categorized into three classes on the basis of their manner of formation: igneous, sedimentary and metamorphic. In this lab you will examine rocks from each of these three classes, identify similarities and differences among them, and answer questions about how and where they formed. Key Terms: Rock Mineral Felsic Mafic Igneous Intrusive Extrusive Sedimentary Depositional environment Metamorphic Learning Outcomes: At the conclusion of this exercise, you will be able to: 1. Identify common minerals on the basis of their color and crystalline structure. 2. Name common igneous rocks and identify the minerals of which they are composed. 3. Identify common sedimentary rocks, characterize the particle size of sediment of which they are composed, and be able to explain the depositional environment in which they were originally deposited. 4. Identify common metamorphic rocks, explain the process through which they were metamorphosed, and identify the original rock type from which they were formed. 7-1

Station 1: Minerals The following graph shows general relationships between six minerals and gives a short description of the important characteristics of each. Use the images provided in the “MineralsImage2” file in WyoCourses under the Lab 7 submodule. Temperature of Formation Color Resistance to Weathering Composition Name Description 1200 o C Dark Weak Mafic (Fe, Mg) Olivine Colored as its name suggests Augite Black, angular Biotite Black, thin sheets Orthoclase Pink, long crystals Muscovite Clear/white, thin sheets 600 o C Light Strong Felsic (Si, Al) Quartz Clear/white, angled crystals 1. Identify each of the minerals based on its characteristics : a. ______ _Biotite _____________ b. _____ Quartz _______________ c. ______ Olivine ______________ d. _______ Augite _____________ e. _______ Muscovite _____________ f. ________ Orthoclase ____________ 2. Compare the following pairs of minerals. For each, circle the mineral that will weather most easily. a. quartz or augite d. olivine or augite b. muscovite or olivine e. biotite or muscovite c. orthoclase or biotite f. quartz or olivine 7-2

d. ______ Basalt ______________ e. ______ Gabbro ______________ 6. Compare granite with rhyolite: a. Which has larger crystals? Granite has larger crystals. b. Are the mineral compositions of granite and rhyolite similar or different? Explain. They have similar mineral compositions. This is due to them both being made composed of quartz and feldspar. There grain size is what makes a difference, but with the composition itself they are the same. c. Which of these rocks took longer to cool and solidify? What does your answer tell you about where these rocks cooled and solidified? Granite took longer to cool and solidify. This information tells us that granite is formed by the slow cooling process deep, beneath the earth’s surface. Compared to rhyolite, which is cooled rapidly at or near the earth’s surface. 7. Where in Wyoming would you be likely to find extrusive igneous rocks? Yellowstone National Park in Wyoming would be a place where you would be likely to find extrusive igneous rocks, due to the features of hot springs, geysers etc. It’s known for it’s volcanic activity stretching back thousands of years. 8. Hawaii is famous for its volcanoes and black sand beaches. What kind of rock would you expect to be most common in Hawaii? The most common rock I would expect to find within Hawaii is basalt. It’s a extrusive igneous rock that forms from the rapid cooling of lava. Due to the dark color of basalt, and considering all the volcanic activity that would end up on the beach, I expect basalt to be the most common rock found in Hawaii. 7-4

Station 3: Sedimentary Rocks Clastic sedimentary rocks are classified based on the size of their constituent particles. Prior to being collected together and formed into rocks, these particles are transported by a variety of processes (wind, rivers, waves, ocean currents). Small particles can be transported relatively easily, in low-energy environments, while large particles are only mobile in high-energy environments. Shale Sandstone Conglomerate Small particles Large Particles Low-energy High-energy Clay, Silt Sand Gravel 9. Identify each of the given sedimentary rocks using the “SedimentaryRocksimage” file in WyoCourses under the Lab 7 submodule. In addition to the rocks above, limestone is also included. Rock Name a. __ Breccia __________________ b. ________ Chert ____________ c. _________ Conglomerate ___________ 7-5

sedimentary structure like sandstone. Sandstone has visible grains. This gives quartzite a glassy appearance. 13. Explain how sandstone can become quartzite. Sandstone can become quartzite through metamorphic processes. This is done through pressure, and heat by way up compression due to tectonic plates and belts. It’s initially buried, then compacted, and the metamorphous process . It finally fuses with quartz grains, resulting in quartzite. 7-7