EarthSci Lesson 3 - Rocks and Minerals

Minerals

naturally occurring chemical compound usually in crystalline form and inorganic in origin and has a specific chemical composition

Physical properties of minerals

• Luster

• Diaphaneity

• Color

• Streak

• Crystal shape

• Tenacity

• Cleavage

• Hardness

• Specific gravity

Luster

ability of a mineral to reflect light from its surface

Diaphaneity

ability of mineral to transmit light (transparent)

Color

not a reliable property due to the impurities that could alter a mineral’s color

Streak

color of the material in powder form, obtained by rubbing it on a porcelain

Tenacity

toughness or resistance to breaking or deforming

Cleavage

breaking/splitting point of a material

Fracture

describes how a mineral break when broken, contrary to its natural cleavage planes

Conchoidal

circular glass shape

Hardness

resistance to abrasion or scratching

Specific gravity

ratio of its mass to the mass of an equal volume of water

Chemical properties of minerals

• Silicates

• Non-Silicates

Silicates

compounds that contain silicone and oxygen

Feldspar

50% of earth’s crust

Quartz

pure silicon and oxygen

Non-Silicates

less abundant, mining

oxides, carbonates, sulfates and halides

precious gems

Diamonds

made up of pure carbon

Rocks

naturally occurring solid aggregate of one or more minerals

Rocks

identified by the minerals they contain and texture, natural

Igneous, Sedimentary, Metamorphic

Three types of rocks

Sedimentary rocks

formed by sediments, grainy

undergoes deposition, found in bodies of water

Metamorphic rocks

originated from pre-existing igneous and sedimentary or even metamorphic rocks

Metamorphism

process that changes preexisting rocks into new forms because of temperature, pressure and chemically active fluids

Contact Metamorphism

happens whenever magma intrudes into rock layers

Regional Metamorphism

large pieces collides and create heat and pressure, subduction zone

Exogenic processes

surface of the crust, outside

Endogenic processes

within the surface, movement of plates, magma

Geologic processes

dynamic actions or events, constantly changes, result of interaction of earth to nature, collaborates with each other

Exogenic processes

includes geological phenomena and processes that originate externally to the Earth’s surface generally related to the atmosphere, hydrosphere, biosphere

Weathering

• mechanical disintegration and chemical decomposition due to weather

• effect of the elements and the action of weather and climate over earth materials

• can be classified or physical

Mechanical weathering

breaking down into smaller pieces, physical change due to weather

Causes of mechanical weathering

• temperature changes and exfoliation

• sand blasting and abrasion

• freeze-thaw cycle and ice wedging

• plant growth and animal burrowing

Chemical weathering

chemical change brought by the different chemicals found on earth, chemical composition

Mass wasting

movement of rock, soil, or other materials down a slope under the influence of gravity

Erosion

caused by natural agents such as water, wind, ice, or waves

Endogenic processes

processes that shape the surface using forces that originate from within the earth

Magmatism

defined as the process of formation and movement of magma

Magma

an extremely hot and viscous mixture of molten and semi-molten rocks beneath the surface of the earth

Reasons of magmatism

• Heat Transfer

• Decompression melting

• Flux melting

Heat transfer

one of the most primary reasons of magmatism

Decompression melting

ground loosens up and melts into magma

Flux melting

has crevices and has water, water meets magma

Flux

means space

Tectonic Plate Theory

all processes was formed in the boundaries, plates moves as a single entity over a plastic mantle

Faults

is a fracture, fissure, zone of fracture between two blocks of rock

Folds

occurs when the crust bends due to compression forces, crust bends away from earth’s surface

Anticline

upward

Syncline

downward

Dip slip fault

inclined fractures where the blocks have mostly shifted vertically

Footwall block

steady

Hanging wall block

moves

Normal Fault

hanging wall block goes downward

Reverse Fault

hanging wall block goes upward

Strike slip Fault

vertical or nearly vertical fractures where the blocks have mostly moved horizontally caused by the shearing forces