mining and its environmental impact. what determines the type of mining? underground v.s. surface...

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