Earth and Space Science / Unit 2: Minerals and Rocks
2.3 Mineral Formation and Resources
Notes
Minerals form when atoms join into crystals in a few main ways.
- Cooling magma or lava: slow cooling allows large crystals; fast cooling makes small crystals.
- Evaporation: water evaporates and leaves dissolved material behind (halite, gypsum).
- Precipitation from hot water solutions, and changes under heat and pressure.
- An ore is a rock or mineral that can be mined for a profit (for example, hematite for iron).
- A gemstone is a rare, hard, attractive mineral. Rubies are the mineral corundum.
Practice
Large crystals in a rock usually mean the magma:
Slow cooling gives atoms time to build big crystals.
Halite crystals forming in a dried-up salt lake formed by:
Dissolved salt is left behind as water evaporates.
An ore is best defined as:
Economic value is what makes a material an ore.
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