Rocks And Minerals Powerpoint 1e2i5o

Rocks and Minerals

Minerals the 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 magmacooling magma causes minerals to crystallize

2. Precipitation • Minerals dissolve out of evaporated water; precipitated

3. Pressure and Temperature

Muscovite

Talc

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

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

Bornite

Mineral Composition Minerals 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)

Gypsum

4. Sulfates and Sulfides - Minerals containing

sulfur

Pyrite

5. Halides -minerals containing

halogen ions plus one or more other elements

Halite

6. Native Elements Minerals that exist in a relatively pure form i.e. Gold, silver, copper

Gold crystal structure

Mineral Properties Mineral PROPERTIES are used to identify minerals based on specific characteristics

Luster Streak Color Specific Gravity Cleavage & Fracture Hardness Magnetism Fluoresence

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 Density= Mass (g) Volume (mL or cm3)

Density of water is 1 g/cm3 Specific Gravity is a ratio, no units

Hardness- measure of resistance of a mineral being scratched

Magnetism

Fluorescence

Magnetite

Double Refraction Calcite 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 rhyolite

granite

• 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 RocksIgneous 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

• Granitic Composition- contain mainly quartz and feldspar, some with biotite mica and amphibole. Make up major rocks of continental crust • Basaltic Composition- contain mainly dark colored minerals and feldspar, along with Mg and Fe. Darker and denser than granitic composition

Classification of Major Igneous Rocks Texture 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- based on formation • Clastic Sedimentary • Chemical Rocks are formed Sedimentary Rocks from weathered bits of are formed when rocks and minerals dissolved minerals precipitate from water • Grouped according to solution size of the sediments Coquina in the rock limestone

• 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 • Metamorphismforms when magma intrudes into existing rock • Changes in rocks are minor

• Regional Metamorphismformed during mountain building process that occur over a large area • Major changes to rocks

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 Rocksform when minerals recrystallize at right angles to the direction of force • Causes a layered or banded appearance

• Nonfoliated Metamorphic Rocksno banded texture • Most contain only one mineral

Foliated

NonFoliated

The Rock Cycle