Rocks and

Minerals

Mineralsthe building blocks of rocks

Mineral Characteristics• natural • inorganic • solid• definite composition• crystal structure

Mineral Formation

4 major processes by which minerals form:1. Crystallization from magma- cooling magma causes minerals to crystallize

2. Precipitation

• Minerals dissolve out of evaporated water; precipitated

3. Pressure and Temperature

• Change in pressure and temperature cause an existing mineral to recrystallize while still solid

Muscovite

Talc

4. Hydrothermal Solutions

• A hot mixtures of water with substances dissolved in them. When they come in contact with existing minerals- a chemical reaction occurs forming a new mineral

Bornite

Mineral CompositionMinerals are grouped or classified based on

their composition. There are 6 groups

1. Carbonates - contain carbon, oxygen, and one ore more metallic element

2. Silicates- formed from silicon and

oxygen - elements combined to

form a silicon tetrahedron, 1 silicon atom and 4 oxygen atoms

- formed from cooling magma

- either near the surface (few crystals) or deep below surface (larger crystals)

3. Oxides

- Minerals that contain oxygen and one or more other element(s)

4. Sulfates and Sulfides

- Minerals containing sulfur

Gypsum

Pyrite

5. Halides

-minerals containing halogen ions plus one or more other elements

Halite

6. Native ElementsMinerals that exist in a

relatively pure form

gold, silver, copper

Gold crystal structure

Mineral Properties

Mineral PROPERTIES are used to identify minerals based on specific characteristics

LusterStreakColor

Specific GravityCleavage & FractureHardnessMagnetismFluoresence

Streak

color of a mineral in its powder form

Color

often not a good property for Iding

Luster

how light is reflected from the surface of a mineral

Cleavage- tendency to break along flat, even surfaces (mica)

Fracture- uneven breakage (quartz)

Specific Gravity- ratio of a mineral’s density to the density of water

Specific Gravity =

mass (g) of dry sample mass lost in water

Specific Gravity is a ratio…so Specific Gravity has no units

Hardness- measure of resistance of a mineral being scratched

MagnetismMagnetite

Fluorescence

Double RefractionCalcite

Smell Sulfur

Rocks and The Rock

Cycle

Rocks- any solid mass of mineral or mineral-like matter that occurs

naturally as part of our planet• There are 3 major type or families or rock:

– Igneous rocks– Sedimentary rocks– Metamorphic rocks

Igneous Rocks

• Magma- molten material underground

• Lava- magma that reaches the surface

• Igneous rocks are formed from magma that has cooled and hardened either beneath the surface or from a volcanic eruption

2 Ways to Form Igneous Rock• Intrusive Igneous

Rocks- form when magma hardens beneath Earth’s surface

• Magma intrudes into existing rocks

• Extrusive Igneous Rocks- form when lava hardens on the surface of the Earth

• Extruded onto the surface

granite

rhyolite

• Magma contains some gases, including water vapor- this make it less dense, so it rises

• As magma rises, it cools and forms crystals

• The longer the cooling time the larger the crystals

Classification of Igneous Rocks Igneous rocks are classified by texture

and composition• Texture refers to the appearance of an

igneous rock (size, shape, arrangement of crystals)

• Composition refers to the proportions of light and dark minerals in the rock

• Coarse- grained Texture- form as a result of slow cooling, ions can move = large crystal size

• Fine-grained Texture- form as a result of quick cooling time, ions lose motion= small crystal size

• Glassy Texture- form from lava that cools rapidly, ions don’t have time to arrange = glassy texture

• Porphyritic Texture- rocks with different size minerals that form from varying cooling rates

• Felsic Composition- contain mainly quartz and feldspar, some with biotite mica and amphibole. Make up major rocks of continental crust

• Mafic Composition- contain mainly dark colored minerals and feldspar, along with Mg and Fe. Darker and denser than granitic composition

Classification of Major Igneous RocksTexture is crossed with composition to classify igneous rocks. For example, granite has a coarse texture due to slow cooling and larger crystals, and a light color from the light colored quartz and feldspar minerals used to form it.

Sedimentary Rocks- formed from compacted and cemented sediments

• Weathering physically and chemically breaks rocks into small pieces called sediments

• Sediments are moved by wind, water, ice, and gravity• Eventually, they are dropped and form layers that are cemented together

Weathering, Erosion, and Deposition

• Weathering breaks rocks down

• Erosion involves weather and the removal of rock

• Deposition is the dropping of sediments • Sediments are

deposited according to size

Compaction and Cementation• Compaction is the

process that squeezes the water out of the sediments. It is caused by the weight of the sediments.

• Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.

• Cementing holds the sediments together.

Classification of Sedimentary Rocks• Clastic Sedimentary

Rocks are formed from weathered bits of rocks and minerals

• Organic Sedimentary Rocks are formed from living materials

• Chemical Sedimentary Rocks are formed when dissolved minerals precipitate from water solution

rock saltlimestone

• Sedimentary rocks hold many clues to the Earth’s history

• Layers of sediments are records of geologic events on Earth

• Fossils are unique to sedimentary rocks

Sedimentary rocks drop according to size; larger particles fall first followed by smaller particles

Metamorphic Rocks- form when existing rocks undergo change through

heat and pressure• Metamorphism means

to change• Most metamorphic

changes occur at high temperatures and pressure

• These occur deep below the Earth’s surface and extend into the mantle

Forms of Metamorphism

• Contact Metamorphism- forms when magma intrudes into existing rock

• Changes in rocks are minor

• Regional Metamorphism- formed during mountain building process that occur over a large area

• Major changes to rocks

Contact metamorphism Regional metamorphism

Agents of Metamorphism

• Heat- causes existing minerals to recrystallize or new minerals to form

• Pressure- causes the spaces between mineral grains to close= more compact rock= greater density

Classification of Metamorphic Rocks- based on texture and composition

• Foliated Metamorphic Rocks- form when minerals recrystallize at right angles to the direction of force

• Causes a layered or banded appearance

• Nonfoliated Metamorphic Rocks- no banded texture

• Most contain only one mineral

Foliated NonFoliated

slate

gneiss

schistmarble

The Rock Cycle

The Rock CycleThinking about relationships among

the major rock groups

Major Rock Groups• Igneous

– Formed from a melt (molten rock)– Plutonic (intrusive):slow cooling and crystallization– Volcanic (extrusion): quick cooling at the surface

•Sedimentary–Formed at the Earth’s surface

–Clastic (Mineral Fragments or grains, clays)

–Chemical (crystalline chemical/biochemical precipitates)

–Organic (made from living material: shells, plants)

•Metamorphic–Changed by pressure, heat and fluids.

Fig. 2.9

MAGMA

46

MAGMA

Crystallization

IGNEOUS

47

MAGMA

IGNEOUS

Intrusive/Plutonic

Crystallization

48

MAGMA

Extrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

Crystallization

49

MAGMAUplift

Crystallization

Weathering

Extrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

50

MAGMA

SEDIMENT

Uplift

Crystallization

Weathering SEDIMENT

Extrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

51

MAGMA

SEDIMENT

SEDIMENTARY

Uplift

Crystallization

WeatheringErosion

Transport

DepositionExtrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

52

MAGMA

SEDIMENT

SEDIMENTARY

Uplift

Crystallization

WeatheringErosion

Transport

DepositionExtrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

53

MAGMA

SEDIMENT

SEDIMENTARY

METAMORPHIC

UpliftBurial

Increased P&T

Crystallization

WeatheringErosion

Transport

DepositionExtrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

54

MAGMA

SEDIMENT

SEDIMENTARY

METAMORPHIC

UpliftBurial

Increased P&T

MeltingCrystallization

WeatheringErosion

Transport

DepositionAdd the

Shortcuts

Extrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

55

MAGMA

SEDIMENT

SEDIMENTARY

METAMORPHIC

UpliftBurial

Increased P&T

MeltingCrystallization

WeatheringErosion

Transport

DepositionExtrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

56

MAGMA

SEDIMENT

SEDIMENTARY

METAMORPHIC

UpliftBurial

Increased P&T

MeltingCrystallization

WeatheringErosion

Transport

DepositionExtrusive/Volcanic

IGNEOUS

Intrusive/Plutonic

• The rock cycle demonstrates the relationships among the three major rock groups

• It is powered by the interior heat of the Earth

• As well as earth’s momentum and…

• The energy from the sun

• It involves processes on the Earth’s surface as well as the Earth’s interior

• It connects the “hydrologic cycle” with the “tectonic cycle”.

In Conclusion…

ROCK CYCLEROCK CYCLE

• The surface of the The surface of the Earth is made of Earth is made of rockrock

• ROCK ROCK is a collection is a collection of one or more of one or more minerals, mixed minerals, mixed together into a solid together into a solid substancesubstance

Rock CycleRock Cycle

• The Series of processes in which rock forms The Series of processes in which rock forms and changes from one type to another by and changes from one type to another by geological processes.geological processes.

PROPERTIES OF ROCKSPROPERTIES OF ROCKS

• BOWEN’S BOWEN’S REACTION SERIESREACTION SERIES: : The pattern that shows The pattern that shows how minerals form how minerals form crystals when they crystals when they cool based on their cool based on their chemical make-up and chemical make-up and melting pointmelting point

The Rock The Rock CycleCycle

-Melting & Intrusion-Solidification of melt-Mountain Building-Uplift & Exposure-Weathering-Erosion & Transport-Deposition & Burial-Metamorphism-Melting & Intrusion

Fig 4.9

The Rock CycleThe Rock Cycle

Fig 4.9

Convergent Plate Boundary-Subducting

slab-Mantle melting-Bouyant rise

of melt

The Rock CycleThe Rock Cycle

Fig 4.9

Convergent Plate Boundary

- Solidification of melt

- Volcanic activity

Intrusive rocks

Extrusive

rocks