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Lab Sedimentary Rocks Rocks & Minerals Name ___________________________ Date _______________ Hour _____ Pre-Lab Questions 1. What are the three sedimentary rock classification categories? 2. List the five steps of lithification and give a brief description of each step (from your notes). Question Using the sedimentary rock samples, and the sedimentary rock identification key, can you correctly identify 7 of the 10 samples on the first try? Background Information ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Hypothesis ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Experiment 1. Obtain the Mineral & Rock Kit, glass plate, a tripod lens. 2. Use the materials and the chart on page 4 to identify each sedimentary rock sample. 3. Ask teacher to approve your samples and then, proceed to complete the data table and the questions. Geophysical Science 1 Lab Sedimentary Rocks Rocks & Minerals Data Table Sample # Name of Sedimentary Rock Class (Clastic, Chemical or Organic) Mineral Composition Possible Sedimentary Environment of Formation Reacts w/HCl Scratches Glass 16 25 55 56 57 / 18 58 61 62 63 65 Conclusion Questions 1. How are the particles that make up the conglomerate different from those that make up the sandstone, or shale? 2. Look closely at the conglomerate sample. What minerals can you identify? 3. Why are fossils rare in conglomerate? Geophysical Science 2 Lab Sedimentary Rocks Rocks & Minerals 4. How do the two limestone samples differ in appearance and in formation? 5. Sedimentary rocks are important to piece together the history of our planet, explain why. 6. Describe the process of lithification in the formation of sedimentary rocks. Geophysical Science 3 Lab Sedimentary Rocks Geophysical Science Rocks & Minerals 4 Lab Sedimentary Rocks Rocks & Minerals ANSWERS Pre-Lab Questions 1. What are the three sedimentary rock classification categories? Clastic Sedimentary rock rock fragments are carried away by wind, water or ice, and deposited. These individual fragments become compacted and cemented together into solid rock. Conglomerate, breccia, shale, sandstone. Chemical Sedimentary rock minerals were once dissolved in water precipitated out (solid in liquid). Gypsum, halite. Organic Sedimentary rock rock that forms from the remains of living things. Coal, limestone. 2. List the five steps of lithification and give a brief description of each step (from your notes). • • • • • Weathering – Exposure Erosion – transportation Deposition – Different depositional environments Compaction – Overlying layers of material decreases volume Cementation – minerals work as glue for grains Question Using the sedimentary rock samples, and the sedimentary rock identification key, can you correctly identify 7 of the 10 samples on the first try? Background Information Classification of sedimentary rock is based on three main factors: 1. The chemical composition of the material that make the rock. 2. The biological (if any) composition of the material the rock is made of. 3. The physical environment that formed the rock. There are three major depositional environments (part of lithification). 1) continental environment lakes, streams, rivers, swamps and floodplains 2) transitional environment coastal (in between marine and continental) 3) marine environment (ocean, salt water) deep and shallow ocean environments Geophysical Science 5 Lab Sedimentary Rocks Rocks & Minerals Data Table Sample # Name of Sedimentary Rock Class (Clastic, Chemical or Organic) Mineral Composition 16 Gypsum Organic CaSO4·2H2O 25 Dolomite Clastic CaMg(CO3)2 55 Fossil limestone Organic Ca(CO3) Thallus slopes, juvenile streams 56 Coal Organic C Swamps Chemical NaCl Shallow marine Organic Ca(CO3) Deep oceans 57 / 18 58 Rock salt (halite) Chalk limestone Possible Sedimentary Environment of Formation Lake, sea water Geologic record Reacts w/HCl Scratches Glass powder yes yes yes 61 Conglomerate Clastic Quartz, mica, clay Beach, rivers 62 Shale Clastic Clay Lake, delta 63 Breccia Clastic Dolomite Thallus slopes, juvenile streams yes 65 Sandstone Clastic Quartz, feldspar Beach, rivers yes yes Conclusion Questions 1. How are the particles that make up the conglomerate different from those that make up the sandstone, or shale? Conglomerate has many particles sizes of different origins while sandstone and shale are more regular in terms of particle sizes. 2. Look closely at the conglomerate sample. What minerals can you identify? Feldspar, quartz, hornblende, calcite, mica 3. Why are fossils rare in conglomerate? Conglomerate was formed in a turbid environment. Fossils need a calm, more stable, environment to form. Geophysical Science 6 Lab Sedimentary Rocks Rocks & Minerals 4. How do the two limestone samples differ in appearance and in formation? Chalk white … formed in the deep ocean Limestone tan … formed in shallow, marine environments 5. Sedimentary rocks are important to piece together the history of our planet, explain why. Sedimentary rocks are where most of the fossils form because it preserves the remains of ancient plants and animals. 6. Describe the process of lithification in the formation of sedimentary rocks. Lithification is the process of rock formation that occurs when rock material (any type of material) is exposed to the environment. • This is known as weathering. • Once the rock is weathered, it can be transported; this is known as erosion. • Weathering (breaking down of rock material) and erosion (transportation of this rock material) are the first steps in the lithification process. • The following are all ways that material can be transported (eroded) in the process of forming sedimentary rocks: Wind, Water, Ice, Gravity. • Then, based on transportation of the minerals, deposition takes place. • Eventually, minerals are compacted and cemented into rocks. Geophysical Science 7