how minerals form section 3.2
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How Minerals Form
Section 3.2
Key Questions
How do minerals form from magma and lava?
How do minerals form from water solutions?
Key Terms
geode
crystallization
magma
lava
solution
vein
Key Concept:
Minerals form as hot magma cools inside the
crust, or as lava hardens on the surface.
When these liquids cool to a solid state, they form
crystals.
Star Fleet Academy
• Minerals form in a process called crystallization.
In crystallization, particles of a substance
form crystals.
Remember, crystals are solids that have their
particles lined up in repeating patterns.
Crystals have flat sides and sharp edges.
Many minerals form when magma or lava cools.
Magma is melted material inside Earth.
Lava is magma that reaches Earth’s surface.
• When magma cools deep under Earth’s
surface, it cools very slowly.
The crystals that form are very large.
• When magma cools closer to the surface, it
cools faster.
The crystals that form are smaller.
• When magma erupts to the surface and forms lava, it cools even faster.
The crystals that form from lava are very small.
Minerals From Solutions (pages 77–79)
Key Concept:
When elements and compounds that are dissolved in water leave a solution, crystallization occurs.
• Substances that form minerals may be
dissolved in water.
“Borax Lake”
The water and dissolved substances form a
solution.
A solution is a mixture in which one substance is dissolved in another.
Some dissolved substances form mineral crystals when
they leave a solution.
Dissolved substances can leave a solution in two
ways.
• Dissolved substances can leave a solution when
the solution evaporates, or turns into gases.
This happens on Earth’s surface.
For example, the mineral halite formed when ancient
seas evaporated.
• Dissolved substances can leave a solution when
the solution cools. This happens below Earth’s surface. Underground
water heated by magma dissolves many substances.
When the water cools, minerals come out of the
solution and form crystals.
• A vein is a narrow band of minerals that lies
between rock layers.
Veins look like streaks of fudge in vanilla fudge ice
cream.
Veins form when solutions of hot water
flow through cracks and then cool. Silver is a
mineral that may form in veins.
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