Sedimentary+Rock+Identification+Lab+Answer+Key
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School
Liberty University *
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Course
210
Subject
Geology
Date
Apr 3, 2024
Type
Pages
4
Uploaded by MateElement8273
1 SEDIMENTARY ROCK IDENTIFICATION LAB Name: Answer Key Date: Objective To identify sedimentary rocks based on grain size, texture, and composition Materials • Clastic/Chemical Sedimentary Rock Charts
• Mohs Hardness Scale (Optional, used in previous lab)
Purpose
(5 pts)
Write 1–2 sentences stating the purpose of this lab. What do you expect to learn? What do you want the outcome to be? There should be complete sentences that answer the questions. Example: The purpose of this lab is to identify sedimentary rocks, identify textures and compositions, and categories (clastic, chemical, organic/biologic.)
Hypothesis
(5 pts)
Write your hypothesis for this lab. It should be 1 sentence and be an if/then statement. (Remember this is your education guess as to what will happen in this lab.) This must be written as an if/then statement. Example: If I read the descriptions of a rock, I can successfully identify a sedimentary rock.
Procedure 1.
Read through all of the steps in the procedure as well as the Data
section. Then complete the Purpose
and Hypothesis
sections. 2.
Using the information provided in the Data
table and the Clastic and Chemical Sedimentary Rock Chart to complete the Data
table and name each sedimentary rock. 3.
Complete the Observations
, Analysis and Conclusion
, and Application
sections before submitting the lab assignment.
2 Data
(60 pts) You may want to refer to the Mohs Hardness scale chart from the Mineral Identification Lab to help you decipher the composition based on hardness. You will also want to keep in mind that calcite reacts with Hydrochloric acid. (2 pts per blank = 60 pts total) Image Number Category (Clastic, Chemical, Organic/Biologic) Texture Hardn
ess Composition or Sediment Name Rock Name 1 Chemical Fine to coarse Crystalline 3 Calcite Travertine 2 Organic/ Biologic Shells & cemented shell fragments 3 Calcite Coquina 3 Chemical Fine to coarse Crystalline 2 Calcite and some shell and skeleton fragments Rock gypsum 4 Organic/biologic Shell & shell fragment cemented with calcite 3 Calcite Fossiliferous limestone 5 Clastic Very Fine (< 1/256 mm) N/A Mud Shale 6 Clastic Medium (1/16 to 2 mm) N/A Sand Sandstone 7 Clastic > 2 mm N/A Gravel (rounded fragments Conglomerate 8 Chemical Very fine crystalline 7 Silica (Quartz) Chert
3 9 Clastic > 2 mm N/A Gravel (angular fragments) Breccia 10 Biologic Fine-grained organic matter N/A Altered Plant Fragments Bituminous coal Data Table 1 Observations
(10 pts)
What do you notice about the differences between clastic, chemical, and organic sedimentary rocks from the samples you looked at? State your answer in 2-3 sentences. Student can reference the size of the grain and the hardness for a comparison. Analysis & Conclusion
(10 pts)
Which characteristic was most helpful in identifying the rock (texture, grain size, composition? Is there any additional information that would have been helpful to you in identifying the rock samples? Did you struggle to identify any of the samples and if so, why? State your answer to these questions in complete sentences. Answers will vary, but it should be written in complete sentences with good explanations to get full credit. Example: Analysis: The most helpful part of identifying a sedimentary rock might be the composition. Composition helps the student, especially if the rock is organic.
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4 Application
(10 pts)
Imagine you are walking in the woods and you come across a gray rock composed of a number of different fossilized organisms such as crinoids, trilobites, and brachiopods, you pour some hydrochloric acid on the rock and notice that it reacts to the acid. Based on this information, what is the name of this rock and what does it tell you about the environment in which it formed? State your answer in complete sentences. It could be either coquina, gypsum, or fossilized limestone. It has to be calcite because it reacts with the acid and it has shell fragments in it. The environment would be an underwater environment where the sediment was laid down in layers and put under pressure to make that type of rock.