mining and its environmental impact. what determines the type of mining? underground v.s. surface...
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Mining Mining
And its environmental impactAnd its environmental impact
What determines the type of What determines the type of mining?mining?
Underground v.s. Surface Mining v.s. Underground v.s. Surface Mining v.s. SolutionSolution– Depth of below surfaceDepth of below surface– Size of the ore bodySize of the ore body– Shape of the ore bodyShape of the ore body– GradeGrade– Type of OreType of Ore
Depth and SizeDepth and Size
Shape of Ore Body
versusversus
Type of OreType of Ore
Is the ore mineral soluble in water?Is the ore mineral soluble in water? Can the ore be melted?Can the ore be melted?
What are the types of What are the types of mining?mining?
SurfaceSurface– StripStrip– Open PitOpen Pit– Placers--DredgingPlacers--Dredging
UndergroundUnderground SolutionSolution
When do you use Surface When do you use Surface Mining?Mining?
Large tonnageLarge tonnage High rates of productionHigh rates of production Overburden (including rock) Overburden (including rock)
is thinis thin
Strip Mining of CoalStrip Mining of Coal
Kansas Geological Survey
Open Pit MiningOpen Pit Mining
Some photos and Some photos and machinery used in open-machinery used in open-
pit miningpit mining
?Dinky Toy??Dinky Toy?
Drilling in pitDrilling in pit
Crushing in pitCrushing in pit
Loading ore in pitLoading ore in pit
Underground Mining
When do we mine When do we mine underground?underground?
The ore deposit is deepThe ore deposit is deep Ore body is steepOre body is steep Grade is high enough to cover costsGrade is high enough to cover costs
Some types of underground Some types of underground miningmining
Room and PillarRoom and Pillar Cut and FillCut and Fill Long wall (coal)Long wall (coal) Shrinkage StopingShrinkage Stoping Block CavingBlock Caving
Room and PillarRoom and Pillar
Cut and FillCut and Fill
Long WallLong Wall
Shrinkage StopingShrinkage Stoping
Block CavingBlock Caving
www.ivanhoe-mines.com/s/Mongolia_ImageGallery
Solution MiningSolution Mining
BeneficiationBeneficiation
Means of separation of ore mineral Means of separation of ore mineral from waste material (or gangue from waste material (or gangue minerals)minerals)
Also known as LiberationAlso known as Liberation
What does it entail?What does it entail?
Crushing and GrindingCrushing and Grinding– Ball mill or rod millBall mill or rod mill
SeparationSeparation– Density (e.g. diamonds with a jig)Density (e.g. diamonds with a jig)– Magnetic propertiesMagnetic properties– Electric propertiesElectric properties– Surface propertiesSurface properties
Refining the OreRefining the Ore
SmeltingSmeltingremoves the metal from the ore mineral removes the metal from the ore mineral by a variety of waysby a variety of ways
Heap LeachingHeap Leaching
removes metal from the ore by removes metal from the ore by solutionsolution
Iron in reviewIron in review
Blast FurnaceBlast Furnace 3CO + Fe3CO + Fe22OO33 2 Fe + 3CO 2 Fe + 3CO2 (gas)2 (gas)
4CO4CO ++ FeFe33OO44 3Fe + 4CO3Fe + 4CO2 (gas)2 (gas)
Sulphide MineralsSulphide Minerals
Are sometimes roastedAre sometimes roasted– Heated in air without melting to Heated in air without melting to
transform sulphides to oxidestransform sulphides to oxides
– Gives off HGives off H22S and SOS and SO22
– Then oxides processed like Fe Then oxides processed like Fe
Sulphides cont’dSulphides cont’d
Process of roasting and smelting Process of roasting and smelting together creates a mattetogether creates a matte– Sulfides are melted into a matte and air Sulfides are melted into a matte and air
is blown through. S is converted to is blown through. S is converted to sulfur dioxide and Fe to iron oxide, and sulfur dioxide and Fe to iron oxide, and Cu and Ni stay in meltCu and Ni stay in melt
SmeltingSmelting
Result at Kidd CreekResult at Kidd Creek
Sulphides cont’dSulphides cont’d
Solvent extraction/electroplatingSolvent extraction/electroplating– Used where rock contains Cu but in too Used where rock contains Cu but in too
little amounts to be recovered by little amounts to be recovered by classical methodsclassical methods
Heap LeachingHeap Leaching
In this process, typically done for Au, In this process, typically done for Au, the ore is not ground, but rather, the ore is not ground, but rather, crushed and piled on the surface. crushed and piled on the surface.
Weak solutions of NaCN (0.05%) Weak solutions of NaCN (0.05%) percolate through the material percolate through the material leaching out the desired metals.leaching out the desired metals.
The solutions are collected and the The solutions are collected and the metals are precipitatedmetals are precipitated
Potential Environmental Potential Environmental ProblemsProblems
A. Mining operation itselfA. Mining operation itself– Disposal of a large amount of rock and Disposal of a large amount of rock and
wastewaste– NoiseNoise– DustDust
BeneficiationBeneficiation Smelting and refiningSmelting and refining
From Underground MiningFrom Underground Mining
SubsidenceSubsidence– Block/cavingBlock/caving– Room and pillarRoom and pillar– Salt mining (Droitwich)Salt mining (Droitwich)
Subsidence in rancher’s Subsidence in rancher’s fieldfield
Subsidence from Pb-Zn Subsidence from Pb-Zn miningmining
From UndergroundFrom Underground
Acid Mine DrainageAcid Mine Drainage– FeS minerals in coalFeS minerals in coal– Sulphide depositsSulphide deposits– Acidic streams can pick up heavy Acidic streams can pick up heavy
elements and transport themelements and transport them
Rock that has acid forming Rock that has acid forming materialmaterial
DrainageDrainage
Acid and open pitsAcid and open pits
Berkley Pit
Other problems with open Other problems with open pitspits
Very large holesVery large holes Pit slopes steep and not stable. Pit slopes steep and not stable.
Cannot be maintainedCannot be maintained May fill with water May fill with water Strip coal mines –loss of top soil in Strip coal mines –loss of top soil in
pastpast– Now smoothed out and top soil addedNow smoothed out and top soil added
Disposal of Waste RockDisposal of Waste Rock
More problematic for open pit than More problematic for open pit than undergroundunderground
Waste rock piles have steep angle of Waste rock piles have steep angle of repose and thus may not be stablerepose and thus may not be stable
Bingham in its hay day produced Bingham in its hay day produced 400,000 tons of waste rock per DAY!400,000 tons of waste rock per DAY!
Tailings pondsTailings ponds
From concentrating usually have From concentrating usually have high pHhigh pH– At Bingham acid waters mixed with At Bingham acid waters mixed with
tailings water to neutralizetailings water to neutralize Different metals have different Different metals have different
problemsproblems
Problems with Problems with Smelting/RoastingSmelting/Roasting
Air: SOAir: SO22 and CO and CO22 and particulate and particulate mattermatter
Noranda Quebec used to have the Noranda Quebec used to have the highest single point source of SOhighest single point source of SO22 in in the world. It may have been the world. It may have been surpassed.surpassed.
CN (Au); NaOH and F (Al); solvents CN (Au); NaOH and F (Al); solvents (electrotwinning); heavy metals; oil (electrotwinning); heavy metals; oil and greaseand grease