Kids collect rocks everywhere, then come the questions. Why is this one sparkly? Why does that one crumble? And what actually is dirt? Here are rocks and soil for kids in plain words: what rocks are made of, the three kinds of rock with Australian examples, how Uluṟu formed, how we use rocks, what soil is made of, and an easy soil test for the garden.
What are rocks made of?
Rocks are made of minerals. The Australian Museum explains that a rock is “a combination of one (such as quartzite) or more (such as granite) mineral particles.” The mix of minerals gives each rock its own properties: its colour, how hard it is, and how big its grains or crystals are.
What are the three kinds of rock?
Geologists sort rocks by how they formed. The Australian Museum describes three ways: “crystallisation of molten magma (igneous rocks), settling of particles (sedimentary rocks), or reheating and pressure applied to pre-existing rocks (metamorphic rocks).” In kid-friendly words:
| Kind of rock | How it forms | Examples | Find it in Australia |
|---|---|---|---|
| Igneous | Super-hot melted rock cools and goes hard | Granite, basalt | Melbourne’s bluestone (basalt), granite from the Bathurst region in NSW |
| Sedimentary | Sand, mud and pebbles settle in layers and harden | Sandstone, conglomerate, shale | Uluṟu, Kata Tjuṯa, Sydney’s Hawkesbury sandstone |
| Metamorphic | Old rock is heated and squeezed until it changes | Marble, slate, quartzite | Marble from Angaston in SA, Castlemaine slate in Victoria |
A few facts children love, all from the Australian Museum:
- Melted rock is called magma when it’s inside the earth and lava when it comes out of a volcano.
- “Fossils are only found in sedimentary rocks.”
- “Some rocks like pumice can float on water.” (Try it in a sink or float experiment.)
- The oldest minerals in the world are found at Jack Hills in Western Australia. They are zircon, and the museum says they are 4.374 billion years old.
How did Uluṟu form?
Parks Australia tells Uluṟu’s story like this. About 550 million years ago, rain washed sand and rock down from tall mountains and dropped them in big fan shapes. One fan was mostly sand, the other mostly rounded rocks. Around 500 million years ago the area was covered by sea, and the weight of the new seabed turned the fans into rock: “The sandy fan became sandstone (Uluṟu) while the rocky fan became conglomerate rock (Kata Tjuṯa).”
About 400 million years ago, as the earth’s plates moved, the rock tilted, and Uluṟu tipped right up by 90 degrees. Over the last 300 million years, the softer rock around it slowly wore away. Uluṟu is a kind of sandstone called arkose, and its red colour is “the rusting of iron found naturally in arkose”. Inside its caves you can still see the rock’s original grey. And like an iceberg, most of it is hidden: Parks Australia says Uluṟu and Kata Tjuṯa continue underground for up to 6 km.
Uluṟu is also Aṉangu land. Aṉangu ask visitors to learn about Tjukurpa, which the park’s culture pages describe as “our traditional law, stories and spirituality”. The Uluṟu-Kata Tjuṯa National Park culture pages, listed in the sources below, are the place to learn more.
How do we use rocks?
Each rock’s properties suit different jobs. A history published by Public Record Office Victoria puts it well: “Sandstone is easier to work but less durable, especially under wet conditions, while granite is durable but harder to work.” Bluestone, a basalt, sat in the middle, “being durable in the wet and easier to work than granite.”
- Bluestone in Melbourne. This dark, hard basalt formed from lava from old volcanoes near Melbourne. It paves the city’s famous cobbled laneways and turns up in kerbs, gutters, steps and building foundations.
- Sandstone in Sydney. The Australian Museum says Hawkesbury sandstone “was used by the early settlers” and is now Sydney’s most valuable building stone.
- Clay in bricks. Bricks are made from fine crushed rock with clay, which “acts as the binding material”.
- Minerals at home. The Victorian Curriculum points to “graphite in pencils and table salt in food”.
What is soil made of?
Soil isn’t just dirt. The Queensland Government describes it as a thin layer covering the earth’s surface, “formed from the weathering of rocks”, and “made up mainly of mineral particles, organic materials, air, water and living organisms”. In other words: bits of broken rock, rotting leaves, air, water and lots of living things. The top layer, the topsoil, is where most roots, earthworms, insects and micro-organisms are busy.
Soil forms very slowly as rocks break down. The Queensland Government says the processes “can be very slow, taking many tens of thousands of years.” Living things help: plant roots grow into cracks and split rock, and “bacteria, fungi, worms and other burrowers” break down dead plants and animals. That’s where soil links to food chains, because decomposers turn dead leaves back into soil.
The rock underneath shapes the soil too. Soils formed from granite “are often sandy and infertile”, while basalt in moist places breaks down into “fertile, clay soils”.
How can you test soil at home?
The Queensland Government’s backyard soil test uses a “sausage-like ribbon”. Here’s a child-sized version.
- Collect. With gloves on, take a spoonful of soil from two or three places, such as a garden bed, under a tree and a sandpit. Put each in a cup.
- Feel. Rub a little between your fingers. Is it gritty or sticky?
- Guess. Which ones will roll into a sausage?
- Wet and roll. Add water a few drops at a time and work it until it holds together, then roll it between your hands or squeeze it out between thumb and finger.
- Check. The Queensland Government says if it “bends like plasticine, it is a clay soil”. If you can see and feel sand and it crumbles, “it is sandy soil”. In between is loam.
Sandy soil lets water drain through fast but holds little water and few nutrients, while clay soils “generally hold more water, and are better at supplying nutrients”. Adding compost or other organic matter helps either kind.
Better Health Channel advises gloves (and a mask) when handling soil, compost or potting mix, and washing hands with soap and water afterwards. Use garden soil, not potting mix: cases of Legionnaires’ disease “have been linked to the use of potting mix.”
What children learn about rocks and soil at school
In Victoria, children in Levels 3 and 4 learn that “rocks, minerals and soils are important Earth resources and have observable properties that enable them to be used in a variety of ways” (VC2S4U06). Examples include looking at local soils with magnifying glasses to spot pebbles, sand, plant matter, earthworms and insects. In the Australian Curriculum (AC9), Year 3 students “compare the observable properties of soils, rocks and minerals and investigate why they are important Earth resources” (AC9S3U02).
KidStudy’s Year 3 Science lesson Rocks and Soil covers rock properties (hard, speckled granite, sandstone made of sand grains, and chalk soft enough to draw with), how we use rocks and clay, from Melbourne’s bluestone laneways to bricks, what soil is made of, and why water drains faster through sandy soil than clay. Its home activity is the soil sausage test. For more hands-on ideas, try our kitchen science experiments.
Questions parents ask
What are the 3 types of rocks for kids?
Igneous rock forms when melted rock cools and hardens, like granite and basalt. Sedimentary rock forms when sand, mud and pebbles settle in layers and harden, like sandstone. Metamorphic rock forms when old rock is heated and squeezed until it changes, like marble and slate.
What kind of rock is Uluṟu?
Parks Australia says Uluṟu is a type of sandstone called arkose. Nearby Kata Tjuṯa is conglomerate, made of pebbles and boulders cemented by sand and mud.
What is bluestone?
Bluestone is a dark basalt, a rock that formed from lava, and an iconic Victorian building stone. It paves many of Melbourne’s old laneways and is used for kerbs, gutters, steps and foundations.
What is soil made of?
Soil is made mainly of tiny bits of broken rock, rotting plant and animal matter, air, water and living things such as worms, insects and micro-organisms.
How long does soil take to form?
A very long time. The Queensland Government says the processes that form soil can take many tens of thousands of years, which is why soil is worth looking after.
Sources
- Learn how to classify rocks, Australian Museum
- Magma, Classification of sedimentary rocks and Metamorphic rocks, Australian Museum
- Building materials, Australian Museum
- Geology and Aṉangu Culture, Uluṟu-Kata Tjuṯa National Park, Parks Australia
- Bluestone sawing in Victoria (Provenance, 2025), Public Record Office Victoria
- From molten lava to cobbled laneways: how bluestone shaped Melbourne’s identity, The Conversation
- What is soil?, What is my soil type? and Soil texture, Queensland Government
- Legionnaires’ disease, Better Health Channel
- Victorian Curriculum F–10 Version 2.0: Science, VCAA
- Australian Curriculum v9.0: Science, Year 3, ACARA