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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 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
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