Minerals and Rocks

Environmental Learning Community

CORC 1332

Sept 21, 2010

Outline

• Quiz

• More on minerals

• Twinkies

• Rocks

How can you identify one mineral from another?

04.03.a

Distinguishing One Mineral from Another

Crystal formCleavage

No cleavage

Color

Luster

04.03.b

Tests to Help Identify Minerals

Hardness

Effervescence

Streak

Magnetism

Density

04.04.a

What Controls a Crystal’s Shape?

Halite (NaCl)

Sizes and packing of atoms

Internal structure of halite

04.04.b

Crystal Lattice

Repeating pattern

Orderly arrangement of atoms

04.04.c1-3

How Are Atoms Arranged in a Mineral?

Cubic Tetrahedron Octahedron

Observe some ways atoms are arranged in a mineral

04.05.a

Atomic Scale of Mineral Cleavage

Sheets joined by long bonds between sheets (break along weakest bonds)

Brown atoms bonded with blue atoms into flat sheets (strong bonds)

Cleave into sheets

04.05.b

Bonds with Same Strength

Mineral breaks through the lattice in nearly any direction so it will fracture

Mineral can break along three sets of planes without passing through an atom

04.05.c

Observe the number of cleavage planes in this mineral

04.05.c

Observe the number and relative orientation of cleavage planes in this mineral

04.05.c

Observe the number and relative orientation of cleavage planes in this mineral

04.06.a1

# is atomic number (number of protons)

Letters are abbreviation for element

Color represents type of element

Periodic Table

Mineral families – Geologist have identified approximately 4000 mineral species.

Out of every kg of material in Earth’s continental crust, only 12 elements are present in quantities greater than one gram: oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, potassium, titanium, hydrogen, manganese, and phosphorus.

04.06.b4

Major Classes of Rock-Forming Minerals

Carbonates

Silicates

Oxides Halides

SulfatesSulfidesNative minerals

Important Minerals• Sulfides: contain sulfur

• Oxides: contain oxygen

• Metals

– Malleable, lustrous, conductors

– Iron, aluminum, copper

• Nonmetallic minerals

• Ore

– Rock with valuable mineral

Silicates

04.09.a

Nonsilicate Minerals: Carbonates

Calcite

Dolomite

04.09.a

Nonsilicate Minerals: Halides and Sulfates

Halite (halide)

Gypsum (sulfate)

04.09.a

Nonsilicate Minerals: Oxides

Hematite

Magnetite

04.09.a

Nonsilicate Minerals: Sulfides

Pyrite

Copper sulfide

Galena

Some important minerals in soils

Primary Minerals – formed by cooling of molten rock

Name Properties

QuartzSilicate

SiO2; hard; weathers very slowly; major component of sands

Feldspar (orthoclase and plagioclase)Silicate

Hard; weathers slowly or moderately to form clay; provides plant nutrients; minor component of sands

Mica (muscovite and biotite)Silicate

Appears to glitter in rocks and sands; provides potassium; weathers to form clays

Dark minerals (e.g., hornblende)Silicate

Easily weather to form clay

Source: Gardiner and Miller, 2008. Soils in Our Environment, 11th ed., p. 6

Some important minerals in soilsSecondary Minerals – formed by precipitated or recrystallized

from solutions that contained elements from the dissolution of other minerals.

Name Properties

Carbonates (calcite and dolomite) CaCO3 and (Ca-Mg)CO3; slowly soluble sources of plant nutrients; common in soils in arid regions

GypsumSulfate

CaSO4-2H2O; soft; soluble materials common in soils of arid regions

Oxide clays (e.g., goethite and gibbsite) Hydrated (containing structural water) microscopic particles formed from iron and aluminum; common in tropical soils

Silicate clays (montmorillonite, illite, vermiculite, kaolinite)

Microscopic particles formed mostly from silica and aluminum; common in soils of temperate climates

Source: Gardiner and Miller, 2008. Soils in Our Environment, 11th ed., p. 6

Minerals & Their Uses

Extracting Minerals

• Locate deposit

• Analyze mineral composition

• Mine for minerals: many different ways

• Process mineral

• Make product

Surface Mining

Near the surface

Less expensive

Overburden removed

Open-pit

Dig quarry

Iron, copper, gravel

Strip mining

Dig trench to extract mineral

Dig parallel trench

Cover old trench with new overburden

Spoil bank

Surface Mining

Subsurface Mining

Minerals deep in ground

Less land disturbance

More expensive

More hazardous

Shaft mine

Direct

vertical shaft

Coal

Slope mine

Slanting passage

Ore hauled in cars

Subsurface Mining

Processing Minerals

Smelting

Melt ore to separate impurities from desired mineral

Blast furnace

Slag disposed of

Mining & The Environment

• Disturbs land

• Land prone to erosion further damage

• Uses a lot of water

• Contaminated streams

• Acid-mine drainage

Impacts of Refining

About 80% of mined ore made of impurities

Tailings

Waste left

behind

Left in piles

Toxic

Impacts of Refining

• Smelting emits pollutants

• Acid precipitation

• Hazardous solid and liquid wastes

• A lot of energy required

Restoration of Mining Lands• When mine no longer profitable

• Prevents further degradation

• Filling in and grading the area

• Planting vegetation

• Surface Mining Control

& Reclamation Act of

1977

• Lands mined for coal

Outline

• Quiz

• More on minerals

• Twinkies

• Rocks

What makes twinkies rise?

What do you think will happen with…?

• Baking powder and water

• Baking soda and water

• Baking soda with vinegar

• Baking soda with vinegar

Leavenings

• Make baked goods like twinkies light and fluffy

• Rocks and minerals with phosphate, sodium and calcium

• Baking soda: sodium bicarbonate

• Baking powder: made from baking soda and phosphate acids

Trona: sodium rich mineralChemistry: Na3(HCO3)(CO3) - 2H2O , Hydrated Sodium

Bicarbonate Carbonate

http://www.galleries.com/minerals/carbonat/trona/trona.jpg

http://www.wma-minelife.com/Brochures/Trona_08.pdf

Lake Gosiute

• Trona deposits

• Formed during Eocene (over 50 million years ago)

• Mountain building period with lots of volcanic ash, organic matter, lake sediments, water, and heat– Conditions right for the

precipitation of trona over 6 million years

Trona

Trona Sodium Carbonate (Soda Ash)

Sodium Bicarbonate(Baking Soda)

Other uses of trona: glass, detergents, making paper

Western phosphate field

• Marine sedimentary rocks

• Deposited about 265 million years ago over a period of about 10 million years

• Rocks consist primarily of organic carbon- and phosphate-rich mudstone, siltstone, phosphorite, carbonate, shale, and chert

Phosphate rock

Phosphate Refineries

• Create monocalcium phosphate and sodium acid pyrophosphate

• Mixed with sodium bicarbonate to make baking powder

Limestonecalcium rich

http://krisdedecker.typepad.com/photos/uncategorized/2008/06/28/limestone_mine.gif

http://images.icnetwork.co.uk/upl/birmmail/may2009/2/5/image-5-for-bid-to-revive-dudley-s-limestone-mines-gallery-24284093.jpg

Outline

• Quiz

• More on minerals

• Twinkies

• Rocks

Key points for rock cycle

Rocks are transformed into different types over time

Igneous: cooling and solidification of molten, material magmaIntrusive

Extrusive

Sedimentary: transportation and deposition of particlesMany different sedimentary environments

Organic and inorganic particles

Metamorphic: formed from igneous and sedimentary rocks through pressure and heat

Igneous rock examples

*BASALTEnvironment of formation = extrusive (volcanic)Texture = fineGrain size = less than 1 mmColor = darkDensity = highComposition = mafic

*GRANITEEnvironment of formation = intrusive (plutonic)Texture = coarseGrain size = 1 mm to 10mmColor = lightDensity = lowComposition = felsic

Metamorphic rock examples

*SCHISTTexture = foliated (mineral alignment) Grain size = fine to medium Type of metamorphism = Regional (platy mica crystals visible from metamorphism of clay or feldspar)Composition = mica, quartz, feldspar, amphibole, garnet

*GNEISSTexture = foliated (banding) Grain size = medium to coarse Type of metamorphism = Regional (high-grade metamorphism, some mica changed to feldspar, segregated by mineral type into bands)Composition = mica, quartz, feldspar, amphibole, garnet, pyroxene

Sedimentary rock examples

*SANDSTONETexture = clastic (fragmental) Grain size = sand (0.2 to 0.006 cm) Comments = fine to coarseComposition = mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks

*LIMESTONETexture = bioclastic Grain size = microscopic to coarse Comments = cemented shell fragments or precipitates of biologic originComposition = calcite

Minerals Rocks

Naturally occurring

Inorganic

Definite chemical composition

Crystalline structure

Physical characteristics

Form in different pressure and heat environments

• Aggregates of minerals

• Differ in mineral composition and texture– Texture: size, shape and

distribution of particles in rocks

Rocks and minerals