Inside the Restless Earth Ch. 1 Minerals of the Earth’s Crust

Inside the Restless Earth

Ch. 1

Minerals of

the Earth’s Crust

Section 1:What Is a Mineral?

Section 1: What is a Mineral?

Mineral: • Naturally formed• Inorganic• Solid • Crystalline structure

Mineral Structure

• element - a substance that cannot be separated or broken down into simpler substances by chemical means.

• Each element is made of only one kind of atom.

The element sodium.

Tom Lehrer's The Elements.mht

Mineral Structure

• compound - a substance made of two or more elements that have been chemically combined.

• Na + Cl = NaCl

The compound halite.

Mineral Structure

• crystal - a solid whose atoms, ions, or molecules are arranged in a definite repeating pattern.

• The arrangement of atoms

is determined by the kinds

of atoms.

Amethyst.

Two Groups of Minerals

Minerals are divided into two groups based on their chemical composition.


1. Silicate minerals - minerals that contain a combination of silicon, oxygen, and often one or more metals.

- Make up > 90% of Earth’s crust

Common Silicate Minerals

Feldspar

KAlSi3O8

Quartz

Silicon Dioxide

SiO2

Mica

Biotite

K(Mg, Fe)3AlSi3O10(F, OH)2


2. Nonsilicate minerals - minerals that do not contain compounds of silicon and oxygen.

Gypsum

Classes of Nonsilicate Minerals

Native Elements - composed of only one element.

GoldCopper


Oxides - form when an element (such as aluminum or iron) combines chemically w/ oxygen.

CorundumAl2O3

Aluminum oxide


Carbonates - contain combinations of carbon and oxygen in their chemical structure.

CalciteCaCO3


Sulfates - contain sulfur and oxygen, SO4.

Gypsum

Calcium Sulfate Dihydrate

CaSO4·2H2O


Halides - form when:

flourine, chlorine, iodine, or bromine

combine with

sodium, potassium, or calcium

FlouriteCalcium Fluoride

CaF2


Sulfides - contain one or more elements (such as lead, iron, or nickel) combined with sulfur.

GalenaLead Sulfide

PbS

Section 2:Identifying Minerals

Section 2: Identifying Minerals

Color

- the same mineral can come in a variety of colors

- usually not the best way to identify a mineral


Luster - the way a surface reflects light.


Luster - the way a surface reflects light.

1. Metallic - bright, reflective

Gold


2. Submetallic - dull, reflective

Euxenite


3. Nonmetallic

Vitreousglassy, brilliant

Pollucite


3. Nonmetallic

Silkyfibrous

Gypsum


3. Nonmetallic

Resinousplastic

Sphalerite


3. Nonmetallic

Waxygreasy, oily

Cancrinite


3. Nonmetallic

Pearlycreamy

Stellerite


3. Nonmetallic

Earthyrough, dull

Kaolinite


Streak - the color of a mineral in powdered form.

- the mineral is rubbed

against a streak plate

- streak is not affected

by air or water

- more reliable than

mineral color

Cleavage and Fracture

Cleavage - the tendency of some minerals to break along smooth, flat surfaces.

Cleavage and Fracture

Fracture - the tendency of some minerals to break unevenly along curved or irregular surfaces.

Conchoidal fracture

Hardness

Hardness - a mineral’s

resistance to being

scratched.

Density

Density - measure of how much matter is in a given amount of space. d = m / v

gold = 19 g/cm3

Specific gravity - the ratio of an object’s density to the density of water.

gold = 19

Special Properties

Fluorescence - glow under ultraviolet light.

Calcite (red) and willemite (green)

Special Properties

Chemical reaction - look for bubbling when combined with an acid.

CaCO3 + 2HCl = CO2 + H2O + CaCl2

calcite hydrochloric acid

Special Properties

Optical properties - such as double refraction.

Same sample of calcite, but it’s rotated.

Special Properties

Magnetism - attracts iron.

Magnetite

Special Properties

TasteNever taste a mineral without the

teacher’s permission.

Borax tastes sweet.

Halite tastes salty.

Special Properties

Radioactivity

Autunite contains uranium.

Section 3:The Formation, Mining,

and Use of Minerals

How Do Minerals Form?

LimestonesAs water runs along the surface of the Earth and

seeps through the ground, it dissolves minerals and

carries them to large

bodies of water, where

they crystallize on the

bottom.


Evaporating Salt WaterMinerals such as halite crystallize when salt water

evaporates.


Metamorphic RocksChanges in pressure, temperature, or chemical

makeup can form new minerals such as garnet.


Hot-Water SolutionsMagma heats groundwater, which now more easily

reacts with and dissolves minerals. The minerals

then crystallize out of

the solution. This

vein of gold was

formed this way.


PegmatitesMagma can move upward into these teardrop-shaped

bodies. Pictured here is a sample of tourmaline from

a pegmatite.


PlutonsAs magma moves

up it may cool and

solidify forming a

pluton.

Mining

Ore:A mineral deposit large enough and pure enough to

be mined for profit.

Mining

Surface MiningUsed to remove minerals located at or near the

surface of the Earth.

Mining

Subsurface MiningUsed to remove minerals

located too deep within the

Earth to be surface mined.

Responsible Mining

Potential mining problems:- Can disturb or destroy habitats

- Waste products may pollute surface water and

groundwater

Responsible Mining

Potential mining problems:- Can disturb or destroy habitats

- Waste products may pollute surface water and

groundwater

Solutions:- Reclamation: return mined land to its original state

- Reduce need for minerals by recycling

The Use of Minerals

Metallic Minerals- Have shiny surfaces

- Do not let light pass

through them

- Good conductors of heat

and electricity

The Use of Minerals

Nonmetallic Minerals- Have shiny or

dull surfaces

- May let light

pass through

them

- Good insulators

of electricity

The Use of Minerals

Gemstones- Highly valued for beauty and rarity

Documents

Inside the Restless Earth Ch. 1 Minerals of the Earth’s Crust