Transcript Minerals
Mineral & Crystal Formation © Beadle, 2009 Minerals What is a mineral? • 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. 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 Evaporation From Cooling Supersaturated Solutions From Cooling Magma & Lava 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 • + Sugar = Solute • Both = Solution (Stuff that dissolves) (Stuff that gets dissolved) • 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 Minerals & Crystals from Magma & Lava Extrusive Cooling: Lava cools Fast (Short Time = Small Crystals) 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. Intrusive Cooling: Magma cools slowly (Long Time = Large Crystals) 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 You can see individual crystals in Granite =cooled slowly V. You can’t see many individual crystals in Rhyolite =cooled very fast Granite 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 Supersaturated Solutions From Cooling Magma & Lava