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Rock Cycle & Minerals Cheat Sheet
A printable reference covering the rock cycle, igneous, sedimentary, metamorphic rocks, mineral properties, Mohs hardness, and crystal structure for grades 6-9.
The rock cycle explains how Earth materials change from one rock type to another over time. This cheat sheet helps students identify igneous, sedimentary, and metamorphic rocks by how they form and by their visible features. It also connects rock changes to Earth processes such as melting, cooling, weathering, erosion, heat, and pressure. Students need these ideas to understand landforms, fossils, plate tectonics, and natural resources. Minerals are the building blocks of rocks, and each mineral has specific physical properties that can be tested. The most important properties include hardness, streak, luster, cleavage, fracture, color, density, and crystal shape. The Mohs hardness scale compares how easily minerals scratch each other, from talc at 1 to diamond at 10. A rock is classified by its origin, while a mineral is identified by its chemical makeup and crystal structure.
Key Facts
- The three main rock types are igneous, sedimentary, and metamorphic, and each forms through different Earth processes.
- Igneous rock forms when magma or lava cools and solidifies, with slow cooling usually making large crystals and fast cooling usually making small crystals.
- Sedimentary rock forms when sediments are compacted and cemented, or when minerals precipitate from water.
- Metamorphic rock forms when existing rock changes because of heat, pressure, or chemically active fluids without fully melting.
- The rock cycle has no single starting point because any rock type can change into another rock type if conditions are right.
- Weathering breaks rock into smaller pieces, erosion moves those pieces, deposition drops them, and compaction and cementation turn them into sedimentary rock.
- A mineral must be naturally occurring, inorganic, solid, have a definite chemical composition, and have an orderly crystal structure.
- Density can help identify a mineral and is calculated with density = mass ÷ volume.
Vocabulary
- Rock cycle
- The continuous process by which rocks form, break down, and change into other types of rock over geologic time.
- Igneous rock
- Rock that forms when molten material cools and solidifies either below Earth’s surface or at the surface.
- Sedimentary rock
- Rock that forms from compacted and cemented sediments or from minerals that crystallize out of water.
- Metamorphic rock
- Rock that forms when an existing rock is changed by heat, pressure, or fluids without completely melting.
- Mineral
- A naturally occurring, inorganic solid with a definite chemical composition and an orderly crystal structure.
- Mohs hardness scale
- A scale from 1 to 10 that ranks minerals by their ability to scratch or be scratched by other minerals.
Common Mistakes to Avoid
- Calling every shiny rock a mineral is wrong because a mineral must meet all five mineral requirements, including definite composition and crystal structure.
- Thinking the rock cycle moves in one fixed circle is wrong because rocks can follow many different paths depending on heat, pressure, melting, weathering, and erosion.
- Confusing magma and lava is wrong because magma is molten rock below Earth’s surface, while lava is molten rock at the surface.
- Identifying minerals by color only is wrong because many minerals can have different colors, and different minerals can share the same color.
- Saying metamorphic rock forms by melting is wrong because complete melting creates magma, which cools to form igneous rock.
Practice Questions
- 1 A mineral sample has a mass of 48 g and a volume of 16 cm3. What is its density?
- 2 A rock has visible layers and contains fossil fragments. Which rock type is it most likely to be, and what evidence supports your answer?
- 3 A mineral can scratch glass but cannot scratch quartz. If glass has hardness about 5.5 and quartz has hardness 7, what is the mineral’s likely hardness range?
- 4 Explain why the rock cycle is better shown as a network of arrows than as one simple circle.