Rocks in the Washing Machine: Exploring Rocks and Minerals

Explorations in Ecology for Children and Their Adults: Transforative Adventures for All of Us

Note: This blog is a serialization of a book titled Explorations in Ecology for Children and Their Adults: Transformative Adventures for All of Us: . Here is the preface. The first adventure is Taking Education Outside.

Introduction

As a child, I loved rocks! Coming home with a pocketful of them is as natural for children as jumping in puddles. That’s how they end up in our washing machines. Kids of all ages, including this old kid, love to skip stones, hold them in our hands, feel their coolness, throw them, collect them, use them as tools, break them open, and build things with them. Rocks also have wide-ranging uses in making artifacts because of their structural strength, thermal properties, and sculptability.

Ecologists distinguish between biotic (i.e., living) and abiotic (i.e., non-living) aspects of ecosystems. Some take this distinction further, imagining rocks and other non-living ecosystem contributors as less than living. Yet, both biotic and abiotic facets of ecosystems are critical participants in the dance of interdependence that is an ecosystem. Many Indigenous cultures recognize this and hold rivers, rocks, and wind as sacred, along with plants and animals (see the beautiful Haudenosaunee Thanksgiving Address for one example). Soil bridges between the abiotic and biotic worlds of European science. It includes biotic and abiotic ecosystem contributors and is where the biotic becomes mineralized and minerals come to life. So, while the distinction between biotic and abiotic ecosystem contributors has utility in some circumstances, rocks and minerals are certainly not less than any of us!  

Warning: Reading this post may increase the likelihood that you’ll find rocks in your washing machines. While most kids naturally enjoy collecting rocks, the activities we describe below are likely to increase their enjoyment of and knowledge about rocks, minerals, and the rock cycle. 

Activity

Collecting Rocks

Nicolette recommends the language of “working rocks” to help kids understand that some rocks have a job and need to stay, like maintaining a path or being a home for bugs. Taking pictures of the rocks can also be a great way to take them home without actually taking them home.

• As you wander the woods, encourage kids to collect rocks including ones they might use for some purpose like throwing, hammering, and breaking open nuts. 

• Ask them what is special about the rocks they choose to collect. 

• Maintain a rock collection at your site. Set up a spot where kids can build a collection of special rocks.

• Encourage sharing of where these rocks were found and what makes them special to the finder.

Sorting Rocks

Your kids can sort rocks based on hardness, texture, color, size, and whatever other criteria the kids come up with.

• Watch for kids sorting rocks or encourage them to, if they're looking for something to do. Suggest they make separate piles of rocks that are similar to each other or if they’re spontaneously sorting, ask them what kinds of rocks are in each pile

• You might offer a challenge to your kids. Ask them to order a collection of rocks from softest to hardest. 

  • Ask them how they might do that. 

  • One way is the scratch test. Rub two rocks together and the rock that loses material and leaves a mark on the other is the softer one.

You can also share some of the information you’ll find in the Nature Science section of this post with your kids and suggest they use that information to sort the rocks into piles based on whether they think each rock is sedimentary, metamorphic, or igneous.

Breaking Rocks

This activity requires protective eyewear. Breaking rocks can be great fun and a way to experience the relative hardness of different kinds of rocks and the texture of rocks that have smooth surfaces resulting from erosion. 

• Let your kids know that they can use one rock to try and break another or use a hammer if you have one. Give them safety suggestions so they avoid smashing their fingers.

• Ask kids about what they discovered banging rocks together or hitting one with a hammer.

  •  How hard is each rock? What’s their texture? Do they have big grains, small grains, or are they smooth? Did you see any holes in the rocks? Any fossils?

Exploring the Rock Cycle

Sedimentary, metamorphic, and igneous rocks are all related to each other and, over geological time, change from one to another depending on their circumstances.

• If you have kids who sorted their rocks into sedimentary, metamorphic, or igneous piles, ask them to arrange their three piles in a triangle on some bare soil.

• Add something to represent magma (melted rock beneath the Earth’s crust) between the metamorphic and igneous piles. Maybe a container with some water in it to signify that magma is a liquid.  

• Add a pile of sandy soil in between the igneous and sedimentary rock piles. Tell the kids that particles that have been deposited on a surface via natural processes are called sediment.

• Add something that represents high heat pressure in between sediment and metamorphic rocks. Perhaps a drawing of steam or a box being pressed together, like below.

• Draw in arrows like below and describe what each arrow represents. You can check the science section below if you need help with how the rock cycle works.

Sorting Soil

As we discuss more fully in the Nature Science section of the Playing in the Dirt activity, soil is composed of crushed rock (clay, silt, and sand), organic matter, water, air, and living beings.

• Ask your kids to gather about a tablespoon of unamended soil from your area. 

• Spill it out on a piece of bark or paper and sort it into at least three different piles. Younger children may pick out big pieces like little sticks or clumps of soil, while older children may sort individual sand grains by color and texture. There is no need to sort the whole tablespoon- the goal is to have three or more sorted piles with three or more particles in each. 

• As they are sorting, ask the children how they are deciding to sort things in each pile.; how are these pieces similar?; how are these piles different from each other? They may or may not be able to answer but asking can encourage them to be curious, too.

You can also ask children to try and guess why the different grains of sand are different colors and textures. Make sure they know that you don’t expect them to know the answer and that you’re just asking for their thoughts and ideas. Older kids may be able to come up with answers like: “Maybe they’re made of different stuff.” 

Identifying Minerals in Rocks

As we’ll discuss in the Nature Science section of this post, rocks generally are chunks of a solid material composed of one or more minerals. You can generally identify the minerals in a rock using their luster, hardness, color, streak, cleavage, and fracture. Luster is how reflective the mineral is. Geologists use the Mohs Hardness Scale to test mineral hardness in the field. This scale goes from one to ten, with one being the softest mineral and 10, the hardness of a diamond, being the hardest. You can use some common objects and a scratch test to get a rough idea of the hardness of the minerals you’ve collected.

• If you can scratch a mineral with your fingernail it has a hardness below 2.5.

• If you can’t scratch it with your fingernail but can scratch it with a copper coin (a penny in the USA), it has a hardness of 3. 

• If you can’t scratch it with a copper coin but can scratch it with a knife it has a hardness above 3 and below 5.5.

• If you can’t scratch it with a knife but can scratch it with a steel nail it has a hardness of 5 or 6.

• If you can’t scratch it with a steel nail it has a hardness of 7 or above.

The next step in mineral identification is to look up mineral identification on the internet or in a field guide to rocks and minerals and use the luster, hardness, color, streak, cleavage, and fracture of your mineral to identify each of them. Your community may have local rock hounds that would love to support you and your kids' findings!

Nature Science

Even before life arose on Earth, our planet was characterized by cycles including the water cycle and the rock cycle. The rock cycle illustrated below describes how the three main forms of rocks transform into each other. 

In addition to the three forms of rocks: igneous, metamorphic, and sedimentary, two other substances play a role in the rock cycle.  Sediments are small particles of mostly mineral matter that are deposited on the Earth’s surface by settling out of solution in the ocean or being deposited by flowing water or other natural means. Magma is liquid minerals at a very high temperature. It is not considered rock because of its liquid state. The above diagram also illustrates how each rock type is formed from the others. Igneous rocks are formed when magma cools and solidifies within (intrusive igneous rock) or above the Earth’s crust (extrusive igneous rock). Metamorphic rocks are formed when either igneous or sedimentary rocks are subjected to extremes of pressure and temperature. Sedimentary rocks are formed when sediments become cemented together.

Igneous rocks often contain large patches of different minerals and never contain fossils. Intrusive igneous rocks are often large-grained because they cool slowly within the Earth allowing time for larger crystals to form. Extrusive igneous rocks cool quickly and so are often shiny or fine-grained. They may have a bubbly texture from gas bubbles created when hot gasses are trapped in them as they cool. Metamorphic rocks are usually pretty hard and are often squished or folded from the pressure under which they form. Sedimentary rocks are soft and are often layered because sediment is often deposited in layers. Clastic sedimentary rocks are pieces of other rocks (pebbles, sand, silt, and clay) that are cemented together. The rock pieces are often visible. Biologic sedimentary rocks are pieces of the remains of living beings. The pieces of remains are often visible.

Even before life arose on Earth, the rock and water cycles played a role in moving materials around on Earth. Life now plays a major role in both of these cycles as well as the carbon and nitrogen cycles. The role of life in many important Earth cycles prompted one of my favorite geologists, Peter Westbroek, to write a book called Life as a Geological Force. The book is unfortunately out of print. I loved the book so much I called him at his home in the Netherlands and asked him why he hasn’t revised the book. He laughed and said that now, in his eighties, he’d rather play his piano.

Glossary

The following glossary includes some science terminology relating to rocks and minerals as well as the names of a few common rocks and minerals.

Elements – The basic building blocks of everything!

Compounds – Combinations of elements bonded together.

Crystal – A compound with a specific microscopic arrangement that often results in particular kinds of macro (i.e., visible) structure. For example, mica minerals cleave easily into sheets.

Minerals – Solid naturally occurring compound with a specific crystalline structure.

Rock – A chunk of one or more specific minerals. Rocks are categorized based on the minerals they contain and how they are formed.

Granite – The rock that many of us live on! It makes up a large proportion of our planet's crust at around 70 to 80%. It is a coarse-grained intrusive igneous rock primarily composed of the minerals quartz and feldspar and also includes mica and other minerals. The decomposed granite sand that makes up a large part of the soil where I live consists of grains of these minerals. 

Basalt - Basalt is the second most common rock in the Earth’s crust found mostly under past or current oceans. It is a fine-grained extrusive igneous rock primarily composed of the minerals feldspar, pyroxene, olivine, biotite, hornblende, and quartz. The vast majority of volcanic rock on Earth’s surface is basalt.

Feldspar - The pink grains in granite that you may find in your soil sorting are orthoclase feldspar. Orthoclase feldspar is a pink mineral in the feldspar group of minerals. It is composed of potassium (the K in NPK fertilizers), aluminum, silicon, oxygen, and hydrogen.

Quartz - Quartz is a very simple silicon dioxide mineral consisting mostly of silicon and oxygen. And more of its atoms are oxygen than silicon. Imagine that! A grain of sand that’s mostly oxygen. Quartz is often milky white or clear but can also take on many different tints. 

Muscovite - The muscovite minerals are a member of the mica family of minerals that are transparent to translucent with a golden tint. Like orthoclase feldspar, it contains potassium, aluminum, silicon, oxygen and hydrogen. Little muscovite flakes (along with the flakes of biotite, another mica mineral found in granite) create the almost glitter-like, sometimes golden, sparkles in decomposed granite soils).                          

Biotite - The biotite minerals are a group of black minerals also in the mica family that contain the elements potassium, magnesium, iron, aluminum, silicon, oxygen, hydrogen, and fluorine. You might mention to the kids that have some idea what oxygen is, that most of the atoms in quartz and the two mica minerals, muscovite and biotite, are oxygen. 

Hornblende - The hornblende minerals are a group of black textured minerals containing the elements calcium, sodium, magnesium, iron, aluminum, silicon, oxygen, hydrogen, and fluorine.

Education Ideas

Think about learning to walk, talk, and do most of the things you do in your daily life. Did you take classes where you sat and listened to other people tell you how to do those things? Probably not. We learn as we interact with and make sense of our environment, including others. When two people interact, symbolic language often plays a role. We do learn by talking with each other, though not so much by sitting still and listening to others talk about ideas we have no clear connection to. Talking with learners generally works best when our talk meets some felt need. Examples of this include using conversations to support learners in finding answers to their questions, offering ideas and techniques to aid someone in accomplishing a task that has meaning for them, and engaging learners in making sense of their own experiences.

What does all of this have to do with helping children learn about rocks? My tagline on my email is, “Walk along with the children and help them learn along the way.” This is what I do both literally and metaphorically. I do not lead. I do offer suggested activities, participate in those activities or whatever the kids come up with, and talk with them in the ways mentioned above. I might suggest looking for special rocks or exploring our rock collection as an activity. I might point out interesting rocks that I see. My favorite times when I’ve explored rocks with kids have come from their interests and self-initiated activities. Here’s an excerpt from one of my journal entries that gives a feel for this.

My favorite occurrence was the impact of all of the kids picking up on “F’s” fascination with mica. Not only did that get all of the kids looking for mica, but it got them all way more involved with looking at the ground and this led to finding all kinds of other rocks and other things. This was a great example of motivation moving through the group like nutrients moving through forests. One of the kids found a pretty piece of feldspar and asked me if it was rare. I answered that it was not and that things can be interesting without being rare!

Another favorite moment was when one of the parents expressed their appreciation of my approach which she described as “simply keeping the Jell-O from sliding off the table” and otherwise giving the kids a lot of freedom.

Their collective interest provided a meaningful context for a brief information-sharing conversation where we talked about the relationships between rocks, minerals, crystals, compounds, and elements. This talking was interspersed with their spontaneous searching for mica, noticing how it cleaves, and seeing how it sparkles.

Wrap Up

Kids love rocks and so should the rest of us! Rocks and minerals have lots of uses for humans and, though they are abiotic, they are important ecosystem contributors. Collecting, sorting, and breaking rocks are all good ways to get to know them better. Hardness, cleavage, texture, and luster can all be used to identify specific minerals in rocks. The three main types of rocks are igneous (cooled magma), metamorphic (change by pressure and heat), and sedimentary (cemented sediment). These types of rocks transform into each other over geological time. Not only do kids love rocks, they also love learning about them when that learning happens while they are engaged in finding answers to their own questions, accomplishing tasks that have meaning for them, and making sense of their own experiences.