Rocks And Minerals Lecture

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Information about Rocks And Minerals Lecture

Published on January 28, 2008

Author: tkelsey

Source: slideshare.net

Rocks and Minerals Chapters 4 - 6

Mineral Naturally Occurring Inorganic Solid Specific chemical composition Definite crystalline structure

Naturally Occurring

Inorganic

Solid

Specific chemical composition

Definite crystalline structure

Naturally Occurring & Inorganic Formed in nature Natural diamonds are minerals Synthetic diamonds are not Inorganic Are not alive, and never was alive

Formed in nature

Natural diamonds are minerals

Synthetic diamonds are not

Inorganic

Are not alive, and never was alive

Question: Is coal a mineral?

Composition Solid Definite Composition – Made up of specific compounds or elements Copper (Cu), Gold (Au), Silver (Ag) Salt (NaCl), Quartz(SiO 2 ) Sometimes composition varies slightly (ex : yellow diamonds)

Solid

Definite Composition – Made up of specific compounds or elements

Copper (Cu), Gold (Au), Silver (Ag)

Salt (NaCl), Quartz(SiO 2 )

Sometimes composition varies slightly (ex : yellow diamonds)

Crystalline structure Crystal – Solid in which atoms are arranged in repeating patterns. Atomic Viewer Minerals form in open spaces and crystals grow to fill the space

Crystal – Solid in which atoms are arranged in repeating patterns.

Atomic Viewer

Minerals form in open spaces and crystals grow to fill the space

Crystal systems

Mineral Formation Magma – As magma cools, the compounds can no longer move freely and chemically interact to form minerals. If magma cools too quickly, you will have no crystals. Solution – If supersaturated, minerals will precipitate. Evaporation – if water evaporates solutions become supersaturated

Magma – As magma cools, the compounds can no longer move freely and chemically interact to form minerals. If magma cools too quickly, you will have no crystals.

Solution – If supersaturated, minerals will precipitate.

Evaporation – if water evaporates solutions become supersaturated

Mineral Groups Silicates (SiO 4 ) Most abundant type of mineral (~96%) Ex : Feldspar, Quartz Tetrahedral Shape (pg 82)

Silicates (SiO 4 ) Most abundant type of mineral (~96%)

Ex : Feldspar, Quartz

Tetrahedral Shape (pg 82)

Carbonates Carbonates (CO 3 ) – Commonly contains metal bonded with CO 3 , combines easily with other minerals. Ex : Limestone, Marble and Malachite

Carbonates (CO 3 ) – Commonly contains metal bonded with CO 3 , combines easily with other minerals.

Ex : Limestone, Marble and Malachite

Oxides Oxide – Metal and oxygen. ex : Hematite and magnetite

Oxide – Metal and oxygen.

ex : Hematite and magnetite

Other mineral groups Sulfides (Element + S 2 ) Sulfate (Element + SO 4 ) Halides (Element + Halide) – NaCl Native element (just an element)

Sulfides (Element + S 2 )

Sulfate (Element + SO 4 )

Halides (Element + Halide) – NaCl

Native element (just an element)

Mineral Identification Color – Caused by trace elements or compounds within a mineral Least reliable clue to mineral identity Luster – The way a mineral reflects light Metallic minerals reflect light Non-metallic do not shine Dull, pearly, waxy or silky

Color – Caused by trace elements or compounds within a mineral

Least reliable clue to mineral identity

Luster – The way a mineral reflects light

Metallic minerals reflect light

Non-metallic do not shine

Dull, pearly, waxy or silky

Mineral Identification Cont’d Texture – How minerals feel to the touch. smooth, rough, ragged, greasy, soapy, glassy

Texture – How minerals feel to the touch.

smooth, rough, ragged, greasy, soapy, glassy

Mineral Identification cont’d Streak – The color of a mineral when it is broken up and powdered.

Streak – The color of a mineral when it is broken up and powdered.

Mineral Identification cont’d Hardness – Measure of how easily a mineral can be scratched. Moh’s Scale 1 – 10 uses basic items that can be carried anywhere (finger nail, iron nail, glass, streak plate)

Hardness – Measure of how easily a mineral can be scratched.

Moh’s Scale 1 – 10 uses basic items that can be carried anywhere (finger nail, iron nail, glass, streak plate)

Mineral Identification cont’d Minerals break along planes where atomic bonding is weak (mica) Cleavage – A mineral that splits evenly along planes Fracture – Minerals that break with rough or jagged edges

Minerals break along planes where atomic bonding is weak (mica)

Cleavage – A mineral that splits evenly along planes

Fracture – Minerals that break with rough or jagged edges

Mineral Identification cont’d Density – Reflects atomic weight and structure of mineral D = M / V Specific Gravity – Measure of density using water Special properties Ex : Double refraction - Calcite

Density – Reflects atomic weight and structure of mineral

D = M / V

Specific Gravity – Measure of density using water

Special properties

Ex : Double refraction - Calcite

Mineral Uses Ores – Mineral that can mined for a profit. Ex : Hematite  Iron Ex : Bauxite  Aluminum Gems – Valuable minerals prized for rarity and beauty. Ex : Rubies and Sapphires, both corundum with trace minerals Under Sea Deposits No owners  international law Not enough technology Destroy oceans

Ores – Mineral that can mined for a profit.

Ex : Hematite  Iron

Ex : Bauxite  Aluminum

Gems – Valuable minerals prized for rarity and beauty.

Ex : Rubies and Sapphires, both corundum with trace minerals

Under Sea Deposits

No owners  international law

Not enough technology

Destroy oceans

Rocks: Mixture of minerals

Igneous Rocks Formed from the cooling of magma Crystallization- formation of crystals Ignis- Latin-”fire” Types Intrusive- cool slowly under Earth’s surface, large crystals Extrusive- cool quickly above Earth’s surface, small/no crystals

Formed from the cooling of magma

Crystallization- formation of crystals

Ignis- Latin-”fire”

Types

Intrusive- cool slowly under Earth’s surface, large crystals

Extrusive- cool quickly above Earth’s surface, small/no crystals

Composition of Magma Slushy mixture of molten rock, gases, and mineral crystals Contain Elements: O, Si, Al, Fe, Mg, Ca, K, and Na Silica (SiO 2 ) is most abundant What factors affect magma???

Slushy mixture of molten rock, gases, and mineral crystals

Contain Elements:

O, Si, Al, Fe, Mg, Ca, K, and Na

Silica (SiO 2 ) is most abundant

What factors affect magma???

Origins of Magma Rocks melt between 800-1220 °C Found in upper mantle or lower crust Geothermal gradient (temperature increase with depth) p101

Rocks melt between 800-1220 °C

Found in upper mantle or lower crust

Geothermal gradient (temperature increase with depth) p101

Melting Temperatures Affected by water content, silica content, Type of mineral in magma Oceanic Crust melts at higher temp, than continental crust  b/c high magnesium and iron, low in water Partial Melting- Not all parts of a rock melt at the same time  different minerals are added to magma at different times, changing type of rock formed

Affected by water content, silica content, Type of mineral in magma

Oceanic Crust melts at higher temp, than continental crust  b/c high magnesium and iron, low in water

Partial Melting- Not all parts of a rock melt at the same time  different minerals are added to magma at different times, changing type of rock formed

Melting Temperatures Cont’d Fractional Crystallization- magma cools and crystallizes in reverse order form melting Removing minerals form the magma

Fractional Crystallization- magma cools and crystallizes in reverse order form melting

Removing minerals form the magma

Bowen’s Reaction Series Predictable pattern of magma cooling Feldspars (calcium rich) change composition to sodium rich rocks gradually Iron-Rich rocks change stepwise with fractional crystallization Rocks form in order of Bowen’s

Predictable pattern of magma cooling

Feldspars (calcium rich) change composition to sodium rich rocks gradually

Iron-Rich rocks change stepwise with fractional crystallization

Rocks form in order of Bowen’s

Crystal Separation Since Olivine changes to pyroxene during cooling, why is found in nature at all? Crystal Separate from magma, preserving olivine

Since Olivine changes to pyroxene during cooling, why is found in nature at all?

Crystal Separate from magma, preserving olivine

Layered Intrusions Sometimes magma cools in layers. These “layered intrusions” often have valuable sources of rare metals

Sometimes magma cools in layers.

These “layered intrusions” often have valuable sources of rare metals

Classifying Igneous Rocks Intrusive/Extrusive Mineral Composition Felsic- light colored, high silica, Contain Quartz and Feldspars Ex: Granite Mafic- dark in color, lower silica, rich in iron and magnesium Ex: Olivine, Amphibole Ultra-Mafic-Very low silica and very high iron, Magnesium

Intrusive/Extrusive

Mineral Composition

Felsic- light colored, high silica, Contain Quartz and Feldspars Ex: Granite

Mafic- dark in color, lower silica, rich in iron and magnesium Ex: Olivine, Amphibole

Ultra-Mafic-Very low silica and very high iron, Magnesium

Classifying Igneous Rock Cont’d Grain size- dependant on cooling rate (fast-smaller) Glassy- Cools very quickly, think air or water cooling lava off

Grain size- dependant on cooling rate (fast-smaller)

Glassy- Cools very quickly, think air or water cooling lava off

Grain Size Fine Grain- Fast cooling Course Grain- Slow cooling Porphyritic- Both fast and slow cooling

Fine Grain- Fast cooling

Course Grain- Slow cooling

Porphyritic- Both fast and slow cooling

Igneous Rocks as Resources Useful building materials  interlocking crystals give strength Resists weathering Ore Deposits  often found in igneous intrusions Veins- Left-overs from Bowen/s Reactions are often valuable gems (gold, silver, lead, copper) Pegmatites- Veins of very large grain minerals (ores and gemstones)

Useful building materials  interlocking crystals give strength

Resists weathering

Ore Deposits  often found in igneous intrusions

Veins- Left-overs from Bowen/s Reactions are often valuable gems (gold, silver, lead, copper)

Pegmatites- Veins of very large grain minerals (ores and gemstones)

 

Diamonds Kimberlites- ultra mafic rock that diamond is found in Found 150-300 Km depth (need VERY high pressure)

Kimberlites- ultra mafic rock that diamond is found in

Found 150-300 Km depth (need VERY high pressure)

Buying Diamonds Color- Range from D-Z (D being colorless and Z being bright yellow J and K are great bargains! Clarity Inclusions- Imperfections inside crystal VS 1-2 even SI 1 good deals

Color- Range from D-Z (D being colorless and Z being bright yellow

J and K are great bargains!

Clarity

Inclusions- Imperfections inside crystal

VS 1-2 even SI 1 good deals

Buying diamonds Cut- Many ways of cutting Beware of brand cuts Carat Weight- Size by weight of your gem ½ carat diamond about $1,500

Cut- Many ways of cutting

Beware of brand cuts

Carat Weight- Size by weight of your gem

½ carat diamond about $1,500

Sedimentary Rocks Sediments- pieces of solid material deposited by wind, water, ice, gravity or chemical precipitation Weathering- breaking down by physical and chemical processes Produces clastic pieces  “broken pieces” Erosion- transport of rock (rain, ice) Deposition- sediment laid down or sinks to bottom

Sediments- pieces of solid material deposited by wind, water, ice, gravity or chemical precipitation

Weathering- breaking down by physical and chemical processes

Produces clastic pieces  “broken pieces”

Erosion- transport of rock (rain, ice)

Deposition- sediment laid down or sinks to bottom

Erosion/Deposition

Formation of Sedimentary Rocks Lithification- process by which sediments turn to rocks Must have thick layers of sediment, increasing pressure and temperature Cementation- a chemical process which mineral growth solidifies sediments

Lithification- process by which sediments turn to rocks

Must have thick layers of sediment, increasing pressure and temperature

Cementation- a chemical process which mineral growth solidifies sediments

Features of Sedimentary Rocks Bedding- horizontal rock layers Graded- large particles fall to bottom Cross- inclined layers move across a horizontal surface (sand dune)

Bedding- horizontal rock layers

Graded- large particles fall to bottom

Cross- inclined layers move across a horizontal surface (sand dune)

Features of Sed. Rocks Cont’d Fossils Patterns-- waves

Fossils

Patterns-- waves

Types Clastic- Course Grain- Round- Conglomerate Angular- Breccia Medium Grain Sandstone-filters drinking water Porosity- % of open spaces Fine grain- Siltstone- traps water

Clastic-

Course Grain-

Round- Conglomerate

Angular- Breccia

Medium Grain

Sandstone-filters drinking water

Porosity- % of open spaces

Fine grain-

Siltstone- traps water

Types Cont’d Chemical- Evaporites- formed from evaporation Salts Organic- remains of once living organisms Limestone Coal

Chemical-

Evaporites- formed from evaporation

Salts

Organic- remains of once living organisms

Limestone

Coal

Metamorphic Rocks Rocks that are changed Meta-change Morphe-form Forces- Heat and Pressure

Rocks that are changed

Meta-change

Morphe-form

Forces- Heat and Pressure

Types of Metamorphism Regional- When Heat/pressure affect large regions or bands

Regional- When Heat/pressure affect large regions or bands

Types of Metamorphism Cont’d Contact (touch)- Edges of batholith touch an area changing the rocks

Contact (touch)- Edges of batholith touch an area changing the rocks

Types of Metamorphism Cont’d Hydrothermal- Hot water (near volcanoes change rock) ex: Brimstone

Hydrothermal- Hot water (near volcanoes change rock) ex: Brimstone

Metamorphic Textures Foliated- wavy bands of crystals Gneiss (formerly granite) Non-Foliated- no visible layers

Foliated- wavy bands of crystals Gneiss (formerly granite)

Non-Foliated- no visible layers

Rock Cycle

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