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Rocks: collecting and classifying

By Peggy Ashbrook

Posted on 2009-06-13

On the playground two sisters collected rocks and set them on a bench where they grouped them by size. When I asked, “What kind of rock is that?” one said, “A triangle” referring to its outer shape. They also had a group based on material— small chunks of concrete were put together because “they have little pieces in them.”
Urban rock collecting is discussed on the Neighborhood Rocks webpage. View the identification pages with your class and ask them if they have seen any of the pictured types of rock before, and where did they see them?
In my east coast urban setting “real” rocks, or rocks naturally in place, are hard to find without excavating. Walking along a creek is one place to find rocks that have been moved there by natural forces, not by humans. Along the Potomac River and its minor tributaries are good places to touch water-worn rocks. (Be sure to wash hands afterwards.) You don’t have to know what type of rock it is, to appreciate that it is smooth and pinkish, or has sparkles, or has holes in it.
Label even the most non-descript rock with the location and date collected, and that single rock becomes the beginning of a scientific rock collection. Maybe a high school earth science teacher would be willing to view the collection and help with scientific names.
In the December 2006 Science and Children, The Early Years column discusses exploring sedimentary rock material with young children with an activity on making pretend rocks. Search the journal archives for “rock” find 22 more articles on teaching about rocks. Young children can experience melting ice, deforming playdough or clay, packing snow or sand into a ball, and the softening of hardened clay in water. In your experience, at what age do they typically understand the Rock Cycle?

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