Unit 3.1: What's this rock I found? Is it valuable?

Beth Dushman, Howard Community College

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Initial Publication Date: September 20, 2024

Summary

In this unit, students will use hand samples or high-resolution images to observe, categorize, and identify some common minerals and rocks, with an emphasis on their role as economic resources. Hands-on activities help students to connect with the materials that they learn about in the rest of Unit 3. Almost every student has picked up a rock at some point in their life and wondered, "what is this?" This unit will help them to recognize the properties of minerals and rocks they could test to identify the sample in question. This unit is aimed at courses where students are expected to learn the basic principles of mineral and rock identification, and will be particularly valuable for students who plan to go on in education -- or anyone who interacts with children!

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Learning Objectives

A successful student will be able to:

  1. Create a reasonable classification system for minerals to understand classification systems
  2. Observe, describe, and identify minerals and rocks using standard geological classification systems
  3. Relate the characteristics of rocks to the geological processes that created the rocks

Context for Use

The unit is appropriate for any introductory Earth science, physical geology, or environmental science course. This unit is designed as part of a larger unit on Earth resources. It is meant to supplement the basic theory of resource formation with hands-on practice. Furthermore, this unit is designed for courses/schools that require a mineral and rock identification component of their Earth Science or geology courses.

Students will practice mineral and rock identification and practice those skills to identify some economically important minerals and rocks. This unit will likely take approximately 3 hours of in-class time. Almost every introductory Geology or Earth Science lab manual and textbook will have a section on mineral and rock identification, but the resources below also have most of the same type of information.

Description and Teaching Materials

Pre-class homework

If the instructor prefers to demonstrate mineral and rock identification in class, the pre-work below can be skipped. In online classes, or if instructors want students to spend more time with samples in class, the videos below provide an overview on how to identify key characteristics of minerals and rocks. These videos were made and edited for an Earth and Space Science class at Howard Community College, so a few comments pertain directly to that class and can be ignored by all other students. Note that the exact samples and sample numbers will vary by institution, but the principles of identification remain the same.

Instructors could also run this section as a jigsaw, with groups of students watching the videos for each group of materials, then sharing with the rest of the class.

Minerals identification:

Igneous Rocks:

Sedimentary Rocks

Metamorphic Rocks

Mineral and rock identification (approximately 5 hours, depending on the number of samples available)

Once geologists know what minerals they are looking for, how do they identify them? In this section, students will be introduced to the principles of mineral and rock identification, with a focus on some of the mineral and rock resources that appeared in previous activities. If classes are face to face, students can use hand-samples. For online students, they can examine images of these samples and describe the skills needed.

Students will complete this geological resource identification worksheet (Microsoft Word 2007 (.docx) 162kB Sep19 24). Students should complete the mineral classification activities first. Then, instructors should work through the Rock Identification PowerPoint slides (PowerPoint 2007 (.pptx) 17.2MB Sep13 24) that provide an introduction to the types of rocks, with some practice questions and images for questions on the worksheet. A guided notes sheet (Microsoft Word 70kB Sep13 24) is available to help students organize their notes from the PowerPoint presentation.

Materials needed: For face-to-face classes, hand samples of minerals and rocks.

  • Suggested rock samples: granite, basalt, gabbro, limestone, sandstone, shale, schist, marble, gneiss
  • Suggested mineral samples: quartz, magnetite or hematite, chalcopyrite, copper, or cuprite, galena;, corundum, lepidolite, bauxite, sphalerite, garnet, sulfur, halite, calcite, kaolinite or other clay minerals (or, whatever minerals you have!)
  • Mineral identification tools: glass plate, ceramic streak plate, piece of copper, hand lens, hydrochloric acid in a dropper bottle (if done in a classroom).
  • Example Mineral Identification chart (Acrobat (PDF) 120kB Aug22 24)
  • Igneous Rocks Identification Chart (Acrobat (PDF) 23kB Feb10 24)
  • Sedimentary Rocks Identification Chart (Acrobat (PDF) 115kB Aug22 24)
  • Metamorphic Rocks Identificaiton Chart (Acrobat (PDF) 80kB Aug22 24)

Teaching Notes and Tips

For the mineral and rock identification part of this activity, students will benefit from interacting with hand samples of common minerals, rocks, and ores. There are several good online resources as well. The mineral and rock identification section will take approximately 3 hours of class time, depending on how many samples are provided and how much background the instructor provides.

Instructors should be comfortable with mineral and rock identification principles.

An open-source textbook chapter on geological resources: https://opengeology.org/textbook/16-energy-and-mineral-resources/

Online rock and mineral images and identification: https://omg.georockme.com/

There are many good Gigapan images of minerals, which may be especially useful for online students. In particular, the Mid-Atlantic Geo-Image Collection (M.A.G.I.C) has many good samples.


Assessment

Students will submit their mineral and rock identification charts. These can be graded in detail, or just checked for completeness, depending on the goals of the instructor (i.e., if mineral and rock identification is a major goal, these should be graded and commented on in detail). Suggested responses and criteria for grading are in the Example KEY for worksheet linked in the Teaching Materials section above.

Assessment standard: Students should clearly identify the distinguishing characteristics of each sample.

References and Resources

SBCTC & Lumen Learning. (n.d.). Reading: Physical Characteristics of Minerals | Geology. Retrieved September 19, 2022, from https://courses.lumenlearning.com/geo/chapter/reading-physical-characteristics-of-minerals/

Brande, S. (2019, July 6). Mineral ID A Practical Online Study Guide. Mineral Study Guide. Retrieved September 19, 2022, from https://omg.georockme.com/

A good resource about geological resources and how they form:

Online mineralogy site from Northern Virginia Community College with many good images:

A few examples of high resolution images of selected minerals and rocks (many more in the Gigapan library):