Common Misconceptions About Rocks and Minerals

Although the research base for geologic misconceptions is not as extensive as that of other disciplines within earth and space science, it is clear that students and teachers alike hold a wide range of incorrect ideas about rocks, minerals, and the rock cycle. To promote accurate scientific instruction, it is important that teachers are cognizant of their own understanding and seek to continually improve their content knowledge. Formative assessment can provide a great deal of insight into student thinking before, during, and after instruction. Finally, teachers should be metacognitive practitioners and reflect on how their methods of instruction may lead to the formation or strengthening of existing misconceptions.


Geologic Misconceptions

Geologic misconceptions can take many forms – the language used to define and describe specimens, relevant properties for classification, the rock cycle, and geologic time.


Communication Breakdown

A major source of geologic misconceptions is the discrepancy between the use of geologic terms in everyday language versus scientific communication. In everyday usage, the term rock refers to a single, particular specimen; to a geologist, the term is used for a category of rock types. A single specimen, geologically speaking, is a clast.

Other words, such as mineral and crystal, are also misused in everyday language. In a study of children and adolescents, students were asked to describe samples of rocks, minerals, and human-made materials. Students did not use the word mineral to describe any samples, and used terms such as rock, stone, and pebble in an intuitive, nonscientific way. It seems that the connotations of these words may supersede any scientific definition or understanding of how these terms should be used.


Size Really Doesn’t Matter

Commonly used definitions also impact how students classify specimens. Several studies note that students often use criteria that are not relevant to a geologist. One such criterion is the size of the specimen, leading students to differentiate between large and small specimens. A consideration of the many common terms used to describe rocks of various sizes (rock, stone, pebble, gravel, boulder, and so on) illustrates why students may consider size to be of utmost importance, while a geologist does not.


Good Looks Are Superficial

Physical appearance, color, weight, and shape are also criteria that may be used by students in classifying a specimen. In one study, students seemed to classify attractive specimens as crystals, while dull or unattractive specimens were considered rocks. While a geologist would divide specimens by their origin or formation, students tended to first group specimens into rocks/nonrocks and then subdivide on the basis of physical characteristics such as size, weight, and appearance.


Longer and Larger Than Life

Geologic misconceptions extend well beyond geologic terms and may include the rock cycle, weathering and erosion, and rock formation. In one study, students tended to describe geologic processes in human time frames rather than on the geologic scale. Students also described processes such as weathering, erosion, and rock formation as dependent on human involvement rather than operating independently of humans. Additionally, not all concepts were equally understood. While the majority of the students could describe erosion accurately, rock formation proved to be much more difficult.

Firmly held beliefs about earth and its history also inhibit the acquisition of scientific knowledge. According to Kusnick (2002), “humans have a deeply felt belief in the stability of the Earth…[which] surfaces in students’ inability to believe in the transience of landscape…The flip side of this belief is that when change does happen, it must be catastrophic.” The difficulty of conceptualizing and accepting long-term, large scale changes in earth’s landforms, such as weathering and the rock cycle, is likely even greater for elementary students, who have limited experience with and understanding of the vast time scales associated with such changes.


Not ‘Just A Rock’

Finally, students may hold misconceptions regarding the utility of geologic concepts. The Grade 6 Science Framework of the Georgia Performance Standards (2007) lists some misconceptions:

Misconception Correct Concept
All rocks are the same, and it’s hard to tell how they originated. Rocks can be distinguished in different types, based on their origins and compositions.
Rocks and minerals are the same thing; distinguishing them is not important. Rocks and minerals are not the same thing; rocks are composed of minerals, which are naturally existing chemical compounds.
Humans can fabricate rocks and minerals; artifacts are the same as rocks and minerals. Rocks and minerals are naturally occurring substances that are usually crystalline and solid.
Minerals are not important to my life. Almost every product we use in daily life contains or depends on minerals that have to be mined.

While thought-provoking and helpful, the misconceptions listed here may only scratch the surface in terms of what your students think about geology. See Probing for Student Understanding for more information about assessing student ideas.

HOW DO THESE MISCONCEPTIONS ARISE?

In general, misconceptions result from students creating their own explanations for how the world works. Often, these ideas are formed well before a student arrives in science class – and serve their purpose well. Numerous studies and anecdotal evidence show that students cling to these ideas even in the face of discrepant events and explicit instruction.


Teaching Makes a Difference, Too

It is important to note that methods and strategies of instruction may also play a role in developing or strengthening misconceptions. Danielle Ford (2005) analyzed third graders’ descriptions of rocks and minerals as part of a FOSS (Full Option Science System) kit unit. She found that while the students were successful in accurately observing and describing minute properties of the specimens, they, like students in other studies, tended to use nonscientific language and include irrelevant properties such as color, shape, size, and weight.

Ford argues that for a geologist, specimen classification is a highly contextualized, discipline-specific activity. Rather than noting all physical properties in isolation, a geologist draws from a rich knowledge of rock types, formation, and characteristics as he or she observes and classifies a particular clast. Elementary students and their teachers often lack this depth of content knowledge and, thus, may not know which properties to attend to and which to ignore. The end result is that a student learns to observe and classify rocks and minerals in a much different way than a geologist.

The integration of language arts and science may also promote the use of nonscientific terms and irrelevant properties. In an effort to save time and promote cross-curricular learning, teachers often pair descriptive writing and the geology unit. Students learn to use precise word choice, adjectives, similes, and metaphors through careful observation and writing.

Subject integration is often necessary and effective, but the danger in this particular pairing is again the confusion of relevant and irrelevant properties and the use of nonscientific language. While describing the unusual shape of a rock may be perfect for a creative writing assignment, it is not useful in identification. In addition, the observation and description portion of the task may become the end itself, rather than the means toward classification. While rocks and minerals do provide an engaging opportunity to teach description, word choice, and creative writing, it may be necessary in this case to separate the geology from the language arts activities.

Furthermore, a geologist’s understanding of individual specimens is inextricably linked to knowledge of igneous, sedimentary, and metamorphic rock as well as the processes of rock formation. These topics are not always introduced at the elementary level, which means that students are learning to describe rocks without linking characteristics to formation. Including an introduction to the types of rocks and rock formation and helping students link what they observe to the process by which a rock formed may help.

See the Teaching the Science section for more information about designing a geologically accurate unit.


Tools for Teachers

Clearly, the discipline of earth science, and particularly the topic of rocks and minerals, is an area in which teachers need to be cognizant of student misconceptions and the implications of their own instructional practices. Formative assessment probes are helpful in gauging some of the ideas that students may bring to science class. In addition, simply being mindful of these issues as you plan and carry out a rocks and minerals unit may be helpful.


Probing for Student Understanding

Volumes 1, 2, and 3 of Uncovering Student Ideas in Science each contain 25 formative assessment probes to help teachers identify misconceptions. The first two volumes of this series contain several probes that relate to geologic concepts such as rocks, minerals, and the rock cycle.

Related formative assessment probes in Volume 1 of Uncovering Student Ideas in Science:

“Cookie Crumbles” asks students to decide how the weight of a whole cookie compares to the cookie broken into pieces and crumbs. It elicits ideas about conservation of matter. Though not directly related, ideas about conservation of matter of ordinary objects will affect students’ understanding of weathering of rocks and the rock cycle.

“Beach Sand” asks students to explain the origin of sand on a beach. It elicits student ideas about weathering, erosion, deposition, and landforms.

Related formative assessment probes in Volume 2 of Uncovering Student Ideas in Science:

“Is it a Rock? (version 1)” asks students to decide whether a number of objects are rocks or not. It elicits student ideas about whether rocks come in many sizes and shapes, as well as their understanding of words such as boulder, gravel, and sand.

“Is it a Rock? (version 2)” asks students to decide whether a number of objects are rocks or not. It is designed to determine if students can differentiate between human-made, “rock-like” materials and geologically formed rocks (even ones shaped by humans).

In addition to these probes, observe your students as they interact, discuss, and write. Observation, note-taking, and interviews with individual students can provide powerful insight into what your students understand about geologic concepts.


Teaching the Science

There are many ways to explicitly promote the development of correct geologic concepts in your elementary classroom. As you design your science unit, consider inviting a local geologist to speak to your class about how geologists observe, describe, and classify rocks and minerals. Brainstorm a list of characteristics (size, color, shape, weight) and discuss which ones are useful in identifying a particular specimen. Consider keeping creative and descriptive writing assignments separate from scientific activities (at least in this particular unit). There is some evidence that with explicit instruction, even elementary students can begin to differentiate between relevant and irrelevant properties.

Also consider linking rock and mineral formation with basic observable properties. For example, students could link evidence from a particular rock (the “holes” in basalt) with the hardening of a bubbling lava flow (Ford 2005). By teaching about igneous, sedimentary, and metamorphic rock, you can help your students begin to develop the background needed to look at rocks and minerals through the lens of a geologist.

In addition to highlighting the formative assessment probes in Volumes 1 and 2 of Uncovering Student Ideas in Science, we’ve created two interactive activities to help assess student ideas and promote the development of geologically correct concepts. These activities are developed in partnership with Content Clips, an interactive web environment designed to help K-12 teachers supplement their curriculum with compelling online resources and activities. By creating a free account, you can save resources and activities (such as these two) to your own collection. You can also create your own interactive activities to use in your classroom.

If you follow the links to the activities listed below, you will enter the site as a guest and will not be able to save them to your own collection. If you wish to save these stories in your own collection, create an account, login, and then search for “rocks.”

What Is It?
This interactive activity involves sorting a variety of images into different categories: rock, mineral, crystal, stone, or other. Use before instruction to assess your students’ use of these terms, or after instruction to monitor progress. An answer key is provided to help you assess student ideas.

Geologic Sorting
This interactive activity is similar to What Is It? Students are presented with 13 images of rocks, minerals, and man-made objects and asked to create their own classification system. While elementary students should not be expected to know all the principles for correctly classifying and sorting specimens (and especially not from images), their responses will provide insight into the properties and principles they attend to while observing rocks and minerals. Individual interviews with students about their work will provide even greater insight into their thinking.

A reference guide provides a simple categorization scheme that might be used by a geologist. Again, elementary students should not be expected to have the “correct” answers in this activity.


National Science Education Standards

Assessing student misconceptions about rocks and minerals and teaching with these misconceptions in mind meets the Earth and Space Science Content Standard of the National Science Education Standards.

Read the entire National Science Education Standards online for free or register to download the free PDF. The content standards are found in Chapter 6.


References

Ford, D. 2005. The challenges of observing geologically: third graders’ descriptions of rock and mineral properties. Science Education 89 (2):276-295. (Abstract)

Georgia Department of Education. 2007. Georgia performance standards: Science frameworks grade 6. www.georgiastandards.org.

Happs, J. C. 1982. Some aspects of student understanding of rocks and minerals. Science Education Research Unit Working Paper 204. University of Waikato, Hamilton, New Zealand (ERIC ED236034).

Kusnick, J. 2002. Growing pebbles and conceptual prisms – understanding the source of student misconceptions about rock formation. Journal of Geoscience Education 50 (1):31-39.


This article was written by Jessica Fries-Gaither. For more information, see the Contributors page. Email Jessica at beyondpenguins@msteacher.org.

Copyright September 2008 – The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 0733024. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is licensed under an Attribution-ShareAlike 3.0 Unported Creative Commons license.

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