Igneous rock identification

Mel Huff

NEO A&M College

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This activity can be used to as an online igneous rock identification lab/activity or to supplement a face to face lab involving igneous rock identification. It is also designed to enforce igneous terms & definitions.

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introductory physical geology course

Skills and concepts that students must have mastered

understanding of the following terms: intrusive, extrusive, composition, texture, mafic, felsic, intermediate, plutonic, volcanic, phaneritic, aphanitic, glassy, porphyritic, pegmatitic, vesicular

How the activity is situated in the course

This is an exercise that summarizes the terms used in class as well as their relationship to one another. In addition, it categorizes common igneous rocks within the context of those terms.


Content/concepts goals for this activity

1) know igneous rock types
2) know intrusive and extrusive
3) know igneous rock types and how to identify each
4) know igneous rock compositions and predominant minerals in each

Higher order thinking skills goals for this activity

1) categorize which textures are intrusive vs extrusive
2) categorize which rocks go with each texture
3) categorize which rocks go with each composition
4) be able to fill in a summary table

Other skills goals for this activity

Description of the activity/assignment

This is an online adaptation to the igneous rock lab that I do in my face to face class. I intend to use this online exercise in my course this fall for students in my face to face class to test. I will update it with information when I find out what does and does not work. I want to test this assignment prior to offering in in a purely online course.

Teaching Tips

Adaptations that allow this activity to be successful in an online environment

There is a link in the assignment for students to practice rock identification prior to identifying the samples in the photographs provided with the lab. I will also be adding a pre-lab quiz on the terms that I do not currently do in my traditional class. In addition, I have added some post-lab questions. The pre-lab quiz and post-lab questions are discussions that I have with my students the day of the lab. By adding these two components, I believe it will strengthen the lab for an online activity.

Elements of this activity that are most effective

I believe that the rock identification practice site will be effective as it will build students' confidence in correctly identifying the rocks, compositions, and textures in the absence of a lab partner or instructor providing immediate feedback and answers to questions. The website provides immediate feedback to the student.

Recommendations for other faculty adapting this activity to their own course:

This assignment can be done either face to face or online. In a face to face class, the instructor will provide the rock samples to identify. In an online class, each sample can be linked to a photograph(s) for identification. I have not uploaded photographs here because I will be using the ones that accompany my textbook (see supporting references for information).

Determining whether students have met the goals

  • Upon completion of the pre-test, students should have a working knowledge of the terms for this activity.
  • Upon completion of the lab activity itself, students should be able to accurately identify common igneous rocks and minerals.
  • If students have successfully accomplished the pre-test and lab activity, students should score at least a 75% on the post-lab questions.

More information about assessment tools and techniques.

Teaching materials and tips

Other Materials

Supporting references/URLs

  • Igneous rock identification by Dave Jessey and Don Tarman through Cal State Pomona – students can use this site as a step-by-step tutorial to identify igneous rock samples. (Note: This site has been taken down. Contact us if you know of a suitable replacement.)
  • Igneous rock identification using photographs by Richard Harwood of Black Hawk College – http://facweb.bhc.edu/academics/science/harwoodr/Geol101/Labs/Igneous/index.htm
  • Textbook information: Reynolds, et al. 2010. Exploring Geology, 2nd Edition. McGraw-Hill Publishing. ISBN: 978-0-07-337668-4