Learning About Rocks

We’ve been studying geology and rocks in science lately.   The kids really enjoy learning about rocks.  It’s been a great exploration of many geologic processes and concepts.

We started by reading quite a few geology books from our personal library and our library in town.  We learned about the layers of the earth and the basic make-up of the planet. We studied volcanoes and the ring of fire.  We also grew crystals and learned about how those form and what they have to do with rocks.  And of course, we read about the three rock families – sedimentary, metamorphic, and igneous.

After the kids were versed in the basics, it was time for some hands-on experimentation.  I spread a bunch of rocks out on our table and provided them with hand lenses to observe the rocks.  We spent quite a long time just finding crystals, checking out the cleavage of various rocks (how they break), and pointing out any neat characteristics we noticed.  We also sorted them into rock families based on our reading.

I decided to teach them another simple concept we hadn’t come across in our books: mafic versus felsic.  Mafic rocks are primarily dark colored while felsic are primarily light.  I drew two circles on the butcher paper table covering and had them sort yet another way.  I had to correct a few of their placements, but overall they did well.  They put a few on the mafic side that had dark inclusions in otherwise light-colored rocks.  Those actually classify as felsic.  Can you spot their mistakes?

We also filled out a Rock Cycle Printable.

Click on the link or the picture to get the free printable.

Of course, we discussed how this cycle doesn’t necessarily keep to the perfect order shown on the printable.  The earth is always moving and rocks change based on their geologic surroundings.

After that, I pulled out a rock and mineral set I purchased from Home Science Tools and gave my kids several rock and mineral identification tables I got from online.  There were 15 specimens in the kit that were numbered, but not labeled.  I added 2 more rocks to it (pumice, which I bought in the cleaning section of our grocery store, and limestone which I had collected at a beach long ago) and then asked my kids to do their best to identify each specimen.  They were amazing!  They performed scratch tests with a nail, streak tests using ceramic tiles, and checked flotation in a basin of water.  They searched for crystals using magnifying glasses, identified some rocks by their smell, and checked the rocks’ cleavage to see how they broke.  Their favorite test was the acid test.  They identified the limestone by seeing that it reacted with the drops of hydrochloric acid they put on it.  They ran all kinds of tests to help determine what kinds of rocks and minerals we were dealing with.

Elizabeth is doing a scratch test on her sample.
Magnetite can easily be identified by seeing if a magnet is attracted to it.
Limestone fizzes when you drop a bit of hydrochloric acid on it.
Pumice floats! Some of the other air-filled igneous rocks also floated briefly before filling with water and sinking to the bottom.
Tyler determining whether or not this rock has crystals. That was always the first question we asked ourselves because the formation or absence of crystals tells you a lot about what kind of rock you’re dealing with.

In the end, we successfully identified all seventeen of our samples.  On occasion, I had to steer them in the right direction or give hints reminding them about a test they hadn’t performed yet, but they did all the tests on their own and did a stand-up job with the whole thing.  It was a terrific culmination to show all that they learned over the past month.  We’re all full-fledged rock hounds now.


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