Mineral & Crystal Formation

Mineral & Crystal Formation

© Beadle, 2009

Minerals• A Mineral is a substance that is:

– naturally occurring, (Not man made)– inorganic (Not living)– A solid crystal – definite chemical composition

• Minerals are the stuff (ingredients) that make up rocks.

• There are over 3800 Minerals Identified.

What is a mineral?

Common Minerals: Olivine

• Rich in Iron– Mantle is made

mostly of this mineral.

Common Minerals: Quartz

• Found in Igneous Rocks – i.e. Granite

• Used for Electronics, Glass & Watches– SiO4

Common Minerals: Biotite

• Found in Igneous Rocks.

• Thin Black Sheets

Common Minerals: Muscovite

• Separates in sheets

• Heat Resistor & Insulator– Used for circuit boards– Windows for heat furnaces.– KAl2(Si3Al)O10(OH,F)2

Common Minerals: Hornblend

• Found in Granite

• Used in decorative dimension stone

Common Minerals:

Plagioclase Feldspar

Formation of Minerals

• Three ways to form mineral crystals:– Evaporation– Cooling down a super saturated solution– Cooling down magma/lava

Crystallization

Mineral crystals can form in three ways:

From EvaporationFrom Cooling Magma & Lava

From Cooling Supersaturated Solutions

Size of Crystal

• Size of the crystal depends on the amount of time it takes to form it.– Long Time = Large Crystal– Short Time = Small Crystal– No Time = No Crystal

Crystallization: The process by which the atoms in the mineral

are arranged to form a crystal structure.– Nucleation – Crystallization

© Beadle, 2009

Mineral Crystals from a Hot Water Solution

Minerals formed from Hot water solutions.

Deep underground, magma can heat water to a high temperature. Sometimes, the elements and compounds that form a mineral dissolve in this hot water.

When the water solution begins to cool, the elements and compounds leave the solution and crystallize as minerals.

Solution Relationship

• Water = Solvent (Stuff that dissolves)

• + Sugar = Solute (Stuff that gets dissolved)

• Both = Solution

• Saturated Solution: When the liquid no longer can dissolve the other substance.

• Super Saturated Solution: As the saturated solution cools down, it has more stuff than it can hold and wants to come out of solution

Minerals from Cooling Solutions

• As the solution cools, the atoms have less and less room to move and when the solution has cooled sufficiently, the atoms link together precipitating the mineral.

Minerals Form from Water Solutions Animations 1, 2

Hot Water Solutions• Pure metals crystallize from hot water

solutions underground in veins – or cracks within rocks. – i.e. silver, gold etc.

Mineral Crystals from Evaporation

Minerals from Evaporative Solutions

Sometimes the elements and compounds that form minerals can be dissolved in water to form solutions.

Solution is a mixture in which one substance is dissolved in another.

When elements and compounds that are dissolved in water leave a solution, crystallization occurs.

Minerals formed by Evaporation

Some minerals form when solutions evaporate. When water evaporates, it leaves behind the

stuff that’s dissolved in it.

Longer it takes to evaporate, the larger the crystal. i.e. salt & water – ocean,

Halite, Gypsum, Calcite.

Demo: Salt & Epson Salt via Overhead

Salt crystals formed from solution because as the water evaporated, the solution left

behind could not hold the same amount of salt, so the salt

precipitates out in crystal form.

Mineral Crystals from Cooling Magma/Lava

Intrusive Cooling:Magma cools slowly

(Long Time = Large Crystals)

Extrusive Cooling:Lava cools Fast

(Short Time = Small Crystals)

Minerals & Crystals from

Magma & Lava

Minerals form from hot magma as it cools inside the crust, or as lava hardens on the surface.

When these liquids cool to a solid state, they form crystals.

Size of the crystal depends on time it takes to cool down.

Minerals from Magma

• If magma cools Slowly, it produces Large Crystals– Long Time = Large

Crystals *(L = L)

Volcanic Neck

Columnar Jointing – Large Crystals

Granite Batholiths

Granite

Granite contains large mineral crystals from cooling deep below the surface. Erosion has exposed the surface of these batholiths many millions of years later.

Lava: Minerals & Crystal Size

Lava: Minerals & Crystal Size

• When the mineral material cools fast, it has smaller crystal size.

• When the mineral material cools slow, it has large crystals.

Rhyolite Granite

V.

You can’t see many individual crystals in Rhyolite

=cooled very fast

You can see individual crystals

in Granite=cooled slowly

Minerals & Crystals from Lava

• If magma cools very rapidly, it produces Glass – NO CRYSTALS!– No Time = No Crystals *(N = N)

Obsidian

And That’s how we get Mineral Crystallization

From EvaporationFrom Cooling Magma & Lava

From Cooling Supersaturated Solutions