1. Section 2 – How Minerals Form
Chapter 4 – Minerals
Section 2 – How Minerals Form

2. How do minerals form from magma and lava?
Key Concepts
How do minerals form from magma and lava?
How do minerals form from water solutions?

3. Introduction
Geode – a rounded hollow rock that is often lined with mineral crystals.
Formed when water containing dissolved minerals seeps into a crack or hollow in a rock.
Slowly, crystallization occurs lining the inside with large crystals that often perfectly formed.

4. Introduction Minerals can form 2 ways
Crystallization – the process by which atoms are arranged to form a material with a crystal structure.
Minerals can form 2 ways
Crystallization of magma and lava
Crystallization of materials dissolved in water.

5. Minerals from Magma and Lava
Minerals form as hot magma cools inside the crust.
Minerals form as lava hardens on the surface
When these liquids cool to a solid state, crystals form.

6. Minerals from Magma and Lava
The size of the crystals depend on several factors:
Rate of cooling.
Amount of gas contained in magma.
Chemical composition of the magma.

7. Minerals from Magma and Lava
Magma deep below the Earths surface
Cools over thousands of years
Slow cooling leads to formation of large crystals
Ex. Amethyst crystals in geode
If undisturbed, growth continues in a regular pattern.

8. Minerals from Magma and Lava
Magma closer to the surface
Cools much faster than deep magma
Rapid cooling leads to small crystal formation
Magma erupting to surface, becoming lava – cools quickly forms minerals with small crystals.

9. STOP and THINK… What is the definition of a solution?
Give an example of a solution.

10. Minerals from Solutions
Quick review:
Solution: a mixture in which one substance is dissolved in another.
When elements or compounds that are dissolved in water leave a solution, crystallization occurs.
Minerals can form in this way underground and in bodies of water.

11. Minerals from Solutions

12. Minerals from Solutions
Minerals formed from evaporation
Dissolve salt into water = solution
Allow the water to evaporate = salt crystals left behind.
Deposits of halite in ancient seas that evaporated – left crystals behind.
Deposits found in Midwest, southwest, along the Gulf Coast.

13. Minerals from Solutions
Minerals from Hot Water solutions
Underground magma can heat water to high temps.
Elements and compounds that form a mineral dissolve in this hot water.
Water solution cools – crystals form
Pure metals that cool form veins
Vein – a narrow channel or slab of a mineral that is different from the surrounding rock
example - Streaks of fudge in vanilla ice cream

14. What did we learn? What is crystallization?
What affects the size of the crystals that form as magma cools?
What are two ways that minerals form from solutions?