Rocks, Minerals, and the Rock Cycle
Use mineral tests and rock textures to infer identity and formation, then trace evidence-based transformations through the rock cycle.
Rocks, Minerals, and the Rock Cycle
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Properties identify minerals; textures reveal rock history
A mineral is a naturally occurring, inorganic crystalline solid with a definite chemical composition. A rock is an aggregate of one or more minerals or mineraloids.
Minerals are identified using several properties together: hardness, streak, luster, cleavage or fracture, density, and special reactions.
melt cools → igneoussediment lithifies → sedimentaryrock changes without melting → metamorphicCooling rate controls crystal size
Slow cooling generally produces larger crystals; rapid cooling produces smaller crystals or glass.
Sediments become rock by lithification
Compaction and cementation bind deposited material.
Metamorphism stays solid
If rock completely melts, its later product is igneous rather than metamorphic.
Foliation records directed stress
Platy minerals can align during metamorphism.
The rock cycle is a network
A rock can follow different pathways depending on processes and environment.
Use PROPERTY → PROCESS → HISTORY
PROPERTY: What hardness, streak, cleavage, grain size, layering, fossils, or vesicles are observed?
PROCESS: Which process creates that feature?
HISTORY: What formation environment is supported?
Use multiple observations before assigning an exact mineral or rock name.
Why it works
UPCAT-style questions often provide evidence and ask for the most defensible history rather than a memorized label.
Five forms you should recognize
Problem: A mineral scratches glass, lacks cleavage, and leaves a white streak.
Reasoning: High hardness plus fracture is consistent with quartz; several properties support the identification.
Problem: Two melts of the same composition form different crystal sizes.
Large crystals support slow cooling underground; tiny crystals support rapid cooling near the surface.
Problem: Granite weathers into grains that are transported, deposited, compacted, and cemented.
The product is a clastic sedimentary rock.
Problem: Limestone experiences heat and pressure without melting.
Its calcite recrystallizes and commonly forms marble.
Problem: A metamorphic rock melts and later solidifies.
Melting erases its previous rock classification; cooling produces igneous rock.
Check before you commit
- Identifying a mineral from color alone
- Confusing cleavage with fracture
- Calling every large-crystal rock metamorphic
- Saying metamorphism requires complete melting
- Treating the rock cycle as one fixed sequence
- Inferring an exact rock name from texture without composition evidence
Do you need the lesson-or just practice?
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Foundations
Build the core procedure with immediate explanations.
Core Practice
Use mixed forms with less scaffolding.
UPCAT-Style Transfer
Apply the competency in unfamiliar representations.
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Rocks, Minerals, and the Rock Cycle FAQ
Why is color often unreliable?
Impurities and weathering can produce different colors in the same mineral.
What is the difference between cleavage and fracture?
Cleavage follows repeated planes of weakness; fracture breaks along nonplanar surfaces.
Can an igneous rock become another igneous rock?
Yes. It can melt and later cool again, possibly under different conditions and with a different texture.
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