Properties of rocks
Compare and group different kinds of rocks based on their appearance and simple physical properties such as hardness, texture, and colour
What a learner can do afterwards
- Describe at least three observable properties of rocks: hardness, texture, colour, grain size
- Sort a collection of rocks into groups based on chosen properties
- Compare two rocks and describe how their properties differ
1 · Read
Rock samples have properties you can compare. Grains are pieces or crystals that make up a rock. Grain size describes how large or small they are, not their colour. Some grains are too small to see without help.
Texture describes how a surface feels, such as rough or smooth. Colour describes what you see, such as grey or red. Hardness describes resistance to scratching. Breaking or crumbling is a different behaviour. Different grains in one rock can have different hardness.
Ask an adult to choose safe samples for a gentle fingernail test. A real scratch is a groove that remains after loose powder is wiped away. A scratched part is softer than your fingernail. If no groove forms, it resisted this test. Do not hit or taste rocks, or breathe rock dust. Wash your hands afterwards.
To sort rocks, choose one property and check every sample. For texture, use rough and smooth groups. For colour, use groups such as grey and red. Two grey rocks belong together in a grey group even if their textures differ.
Two white rock samples can react differently to a scratch test. One may show a groove while the other resists scratching. Their colour matches, but their scratch resistance differs. Those observations alone do not tell you what kinds of rocks they are.
Check hardness, texture, colour, and grain size, then sort your rocks into groups.
This lesson, its questions, and its flashcards were written for this dataset.
The reading was written for this dataset.
More to read
Compare rock samples
Ask an adult to choose clean, safe samples. Look at their colours and visible grains. Gently feel each surface. Choose one property for sorting and use the same rule for every sample. Two grey rocks can share a colour group even when one is rough and the other smooth.
Hardness describes resistance to scratching, not breaking. With adult help, try a gentle fingernail test. Wipe away loose powder and check for a groove. A real groove shows that the tested part is softer than the fingernail. A powder mark alone does not show this. Do not hit or taste rocks, or breathe rock dust. Wash your hands afterwards.
2 · Watch
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Where it sits
Learn first
Nothing; this is a starting point.
Optional connections
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.