Investigating Rock Classification

Revising authors: Sean Bryan, Colorado State University; Megan Plenge, University of North Carolina Chapel Hill

Original authors:Laurel Robinson, SUNY Westchester Community College; Joanna Hodge, Fleming College; Karen Yip, Houston Community College System; Sean Bryan, Colorado State University; Chelsea Lancelle, University of Wisconsin-Platteville

Initial Publication Date: August 11, 2021 | Reviewed: August 4, 2022

Summary

Average inquiry level: Structured

This lab activity provides an introduction to rock classification. Classification is useful because it allows scientists to identify patterns and organize information. In this lab, students investigate rocks by developing their own classification schemes. They then learn how scientists classify rocks, and make connections to rock formation processes. This lab is designed for face-to-face instruction.

Learning objectives for this lab activity:

  • Identifying types of observations that are useful in identifying rocks
  • Categorize rocks based on observable physical characteristics, and explain why classification is an important aspect of science
  • Classify rocks as sedimentary, igneous, or metamorphic, and justify why each rock is included in its classification group
  • Reflect on how their classification schemes compared to the one used by geologists

Key words:rock classification, observation, identification, inquiry, igneous rocks, sedimentary rocks, metamorphic rocks, jig-saw activity

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Context

Audience

This lab activity is designed for an introductory-level Physical Geology or Earth Science course.

Skills and concepts that students must have mastered

Students are assumed to have already had a lab on minerals, but no other labs on rocks are assumed.

How the activity is situated in the course

This lab is is a stand-alone lab activity. It is designed to be used early in the course an initial, introductory lab to rocks. It is designed to be used in a face-to-face mode.

Goals

Content/concepts goals for this activity

1. Identifying types of observations that are useful in identifying rocks
2. Categorize rocks based on observable physical characteristics, and explain why classification is an important aspect of science
3. Classify rocks as sedimentary, igneous, or metamorphic, and justify why each rock is included in its classification group

Higher order thinking skills goals for this activity

1. Reflect on how their classification schemes compared to the one used by geologists

Other skills goals for this activity

Other skill goals for this activity in include observation skills, group collaboration skills.

Description and Teaching Materials

Lab activity is broken into three parts:
Part 1: In small groups, students develop their own classification scheme for a set of rock samples. Students are then jig-sawed into new groups, where they compare, evaluate, and revise their classification schemes using a new set of samples.
Part 2: Students develop the basic scientific classification scheme (Igneous, Sedimentary, Metamorphic; with sub-catagories) during an Instructor-led discussion. Students then categorize samples according to this classification scheme, with opportunities for feedback and formative assessment.
Part 3: Students reflect on their classification schemes and the one used by geologists.

Materials needed: Students must have examples of at least 15-20 igneous, sedimentary, and metamorphic rocks. Samples are divided into Sample Group A and Sample Group B. Suggestion for Group A: granite, gabbro, basalt, pumice, rhyolite, gneiss, marble, phyllite, limestone, conglomerate, shale, sandstone. Suggestions for Group B: porphyritic rhyolite, diorite, obsidian, quartzite, schist, slate, different sandstone, siltstone, breccia.
Students should also have a hand lens; dilute hydrochloric acid is also helpful.


Investigating Rock Classification - Student Worksheet (Microsoft Word 2007 (.docx) 27kB Jul28 21) 
Investigating Rock Classification - Instructor Instructions (Microsoft Word 2007 (.docx) 605kB Jul28 21) 

 

Teaching Notes and Tips

Please see the Instructor Instructions file.


Assessment

We suggest grading most of the lab based on completion. Formative assessments include:
(Learning objective 1) Part 2, question 1.
(Learning objectives 2,3) Part 2, questions 2 and 3. The tables allow students and instructors to assess how well students were able to classify rocks, and to see if students improved after getting instructor input.
(Learning objectives 4) Part 3, question 1
An optional summative assessment could be the successful identification of Sample Group B samples for Part 2, question 4.

References and Resources

General information on rocks: https://www.nps.gov/subjects/geology/rocks.htm
Open geology textbook for background information: https://opengeology.org/textbook/ 
Geoscience videos on rocks: https://www.youtube.com/playlist?list=PL4Wzj82Z15gwKjVTd8d0uHvRx4NbKs7gr