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 & WatchesWatches –SiO 4

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. –KAl 2 (Si 3 Al)O 10 (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 Evaporation From 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. –NucleationNucleation –CrystallizationCrystallization © 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, 212

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 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 Evaporation From Cooling Magma & Lava From Cooling Supersaturated Solutions