Weekend Science Fun: More Rocks, Crystals, and Fossils for Kids

Our post today was inspired by the Let’s Rock series of books, as well as a visit to the Flagg Gem and Mineral Show that is being held in Mesa, Arizona this weekend (Jan. 6-8, 2012). The show is a great place to take kids, with a lot of child-friendly booths.

About the Let’s Rock series books (which just came out in paperback this month):

1. Crystals by Richard Spilsbury and Louise Spilsbury explains what crystals are and how they form. The text includes mini-biographies of scientists who made important discoveries about crystals, and also includes hands-on activities, such as panning for crystals and growing your own crystals. It is packed with fascinating information.

Crystals are minerals that form in such a way that they reach their optimal shape, often having clearly defined sides, corners and edges. Crystals either grow from magma as it cools, or form when water containing loads of dissolved minerals slowly evaporates. The types that come from water may form at the surface or in caves deep underground. The book has an amazing photograph of gypsum crystals that formed in a cave that are so big they dwarf the men climbing on them (or you can see the photograph at National Geographic).

This is a calcite crystal my son got at the show. Calcite is an abundant mineral, probably the most common. It comes in a variety of colors and shapes. Some forms, such as the pink calcite here, may flouresce under UV light and phosphoresce (continues to glow) after it has been in the sun.

Crystal Activities:

A. Test to see if a crystal contains calcite


  • Crystals to test
  • Acid, such as weak hydrochloric (strong vinegar may work)
  • Dropper

You can tell if a crystal contains calcite by applying a few drops of an acid to the surface. Calcite will release carbon dioxide gas when treated with an acid, causing bubbles to form.

You can see the results in this video:

B. Open a geode

A geode is hollow roundish-shaped rock that often contains crystals. Obtain a geode from a rock shop, show or online and then crack it open. Note:  It’s always a good idea to wear eye protection when using hammers on rocks. Once you know what a geode looks like, keep you eyes open for naturally occurring ones.

Edit: Or you can make a homemade geode.

Can you spot the garnet crystals in this rock?

More related activities:

Growing crystals here at Growing With Science

Grow Spikes of Crystals in the Sun at Exploratorium

2. Fossils by Richard Spilsbury and Louise Spilsbury discusses how fossils form, where they are found, and also gives instructions for making your own trace fossil using plaster. Budding geologists are going to love this fact-filled book.

As a biologist who studies living creatures, I find myself drawn to the fossils. I added a few to my collection yesterday, although I left behind a lovely trace fossil of spider footprints that was very cool!

Fossil Search Activity:

One of the booths at the Gem and Mineral show had a bin full of sand filled with small fossils, which is a fun searching activity for young children.


  • play sand
  • large bin (or sandbox)
  • small fossils (available online or at shows)
  • colander or other tools for sifting sand (optional)
  • hand lens or magnifying glass to examine the fossils closely

Place the sand in a bin or sandbox. Mix in sample fossils and let the children hunt for them. If your children are interested in dinosaurs, a few small plastic dinosaurs might be a fun addition, too.

Coral fossil

Shell fossil

Leaf fossil

Other posts with related activities:

Archelon and Other Fossils

Petrified Wood

3. Metamorphic Rocks by Chris Oxlade examines what metamorphic rocks are, how they form and some common types. The book contains instructions for making a model metamorphic rock out of clay and chocolate, as well as suggestions of books and websites where you can find out more.

Rocks are grouped into three types:  igneous, sedimentary and metamorphic. Metamorphic rocks are formed when the other two types, igneous or sedimentary, are exposed to extremes in temperature and/or pressure, or sometimes chemicals (especially in hydrothermal solutions). Typically this occurs deep within the earth.

Metamorphic rocks often have bands or layers of color where the mineral segregated during formation.

For example, see the bands in this sample of gneiss, a metamorphic rock:

One of our favorite demonstrations of how metamorphic rocks forms is a machine at Arizona State University that turns ordinary table salt and pepper into a hard rock. How? The secret is that the machine applies a good deal of pressure and the two substances meld together. It is very cool! We saw this at the Earth and Space Exploration Day.

Common metamorphic rocks include marble (from limestone), slate (from shale), quartzite (from sandstone), gneiss (often from granite) and schist. See page 17 in the book for hints for identifying each type.

Metamorphic Rock Activity:

Because metamorphic rock is often harder than other types of rocks, it is used for buildings and statues. Look for slate or marble floors, marble statues and headstones, slate tiles, quartzite blocks, counter tops etc. in public buildings near you.

Leave us a comment and let us know what you find.

Found out more about rocks and minerals

Books (Affiliate links go to Amazon):

Crystals (Let’s Rock) by Richard Spilsbury and Louise Spilsbury

Reading level: Ages 8 and up
Publisher: Heinemann Raintree (January 1, 2011)
ISBN-10: 1432946927
ISBN-13: 978-1432946920

Fossils (Let’s Rock) by Richard Spilsbury and Louise Spilsbury

Reading level: Ages 8 and up
Publisher: Heinemann Raintree (January 1, 2011)
ISBN-10: 1432946900
ISBN-13: 978-1432946906

Metamorphic Rocks (Let’s Rock) by Chris Oxlade

Reading level: Ages 8 and up
Publisher: Heinemann Raintree (January 1, 2011)
ISBN-10: 1432946889
ISBN-13: 978-1432946883

Books were provided by publisher for review purposes.


  1. Chad Gleaves

    I am glad to have read this post. Thank you so much for enriching my knowledge about fossils. A very similar site that I have once visited is http://fossilsforkids.net/. Maybe some of your readers can also check it out and try to compare some facts. Thanks!

  2. betty rodgers

    i am just learning, tho i am not a kid i am retired, and 75 years old, thanks so much. i guess this is the way to learn. i have found a lot of small river rocks, fosils, and minerials and i love it. betty rodgers

  3. Roberta


    Good for you!

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