Muhammad Ridha Adhari, S.T., M.Sc

Dept. of Geological EngineeringFaculty of EngineeringSyiah Kuala University

Darussalam, Banda Aceh2014

OUTLINE

INTRODUCTION

EXPLORING FOR METAL

METAL PROCESSING

ENVIRONMENTAL CONCERN

SUMMARY

REFERENCES

INTRODUCTION

Copper

Gold Aluminium

Iron

Batteries - cadmium, lithium, nickel and cobalt

Circuitry - gold, copper, aluminum, steel, silver, lead andzinc

Computer and television screens - silicon, boron, lead,phosphorus and indium

Cosmetics and jewellery - gold, diamonds, iron oxide,zinc and titanium dioxide

Electricity - coal and uranium

Fertilizer - phosphate, nitrogen, sulphur and potash

Musical instruments - copper, silver, steel, nickel, brass,cobalt, copper, iron and aluminum

Surgical instruments - stainless steel

Vehicles and tires - steel, copper, zinc, barium,graphite, sulphur and iodine

Housing construction - gypsum, clay, limestone, sandand gravel

It is difficult to imagine life without iron, aluminum,copper, zinc, lead, gold, or silver. These and othermetallic resources mined from the Earth are vitalbuilding blocks of our civilization — and society’sneed for them is increasing.

Why does society need metals? Metals are a class of chemical elements with very useful

properties, such as strength, malleability, andconductivity of heat and electricity.

Most metals can be pressed into shapes or drawn intothin wire without breaking, and they can be melted orfused.

Some metals have magnetic properties, while others arevery good conductors of electricity.

For example, gold is used in electronic equipmentbecause it is an exceptional conductor of electricity andheat and it does not tarnish or corrode.

Metals and other minerals are essential components insuch everyday necessities as our homes, cars,appliances, and tools.

Indeed, we find ourselves becoming increasinglydependent on a vast array of new technologies —computer information systems and global communicationsnetworks — all of which need metals.

Metals are also integral to the basic infrastructure of oursociety: transportation systems (highways, bridges,railroads, airports, and vehicles), electrical utilities forconsumer power, and food production and distribution.

As the Americanpopulation increases andour standard of livingadvances, so does ourneed for metals. We nowuse three times as muchcopper and four times asmuch lead and zinc as wedid 75 years ago.

The increasing need formetals in the UnitedStates is a need sharedthroughout the world.

US consumption of Copper,Lead, and zinc

What are the principal sources ofmetals? Metals come from rocks and minerals in the Earth’s crust.

Minerals are naturally-formed chemical elements orcombinations of elements that have specific chemicalcompositions and physical properties.

Metallic and nonmetallic minerals occur in ordinary rocksthroughout the Earth’s crust, but only a few mineralscontain high enough concentrations of metals to be minedprofitably.

Certain metals, such as copper, lead, and zinc have astrong natural affinity for the element sulfur, and theycombine with it to form minerals called sulfides.

Special geologic processes lead to the development ofmineral deposits having high concentrations of metal-bearing minerals. These types of mineral deposits arerare, and they occur in very diverse locations.

Large mineral deposits are being mined today fromvarious environmental and geographic settings, suchas high mountainous rain forests located in Indonesia,arid deserts in Arizona, and the treeless Arctic tundra ofAlaska.

The Grasberg Mine, Papua , is thelargest gold mine, the third largestcopper mine and highest open pitmine in the world. The mine hasproduced 610,800 tones of copperand 58 tones of gold in 2006.

At 3.5 km long, 1.5 km wideand 360 m deep, theKalgoorlie Super Pit isAustralia’s largest open cutgold mine.

Located in the North SlaveRegion of the NorthwestTerritories, Canada,, the DiavikDiamond Mine produces 8million carats or 1600 kg ofdiamonds annually. The mine isgouged into a 20 square kmisland.

Underground Mining

Mining cycle

The geologic evolution of the Earth controls the quantityand the very uneven distribution of metal resources in theEarth’s crust.

Discovering metal-rich deposits commonly requiresextensive searching, and exploration is the the first step inthe mining cycle.

Once exploration geologists find an area with metals, theydetermine whether it is of sufficient size and richness to bemined profitably. If the deposit is rich enough, activities toextract the metals from the Earth begin.

Extraction, the next part of the cycle, involves mining toremove the metal-bearing minerals from the Earth, mineralprocessing (beneficiation) to concentrate the metal bearingminerals, and smelting to liberate metals from the mineralsthat contain them.

Mine closure is the final step in the mining cycle. Miningeventually depletes the metal-rich material that could beeconomically removed at a specific mine.

When mining can no longer be profitably conducted, themine and related facilities used in beneficiation or smeltingwill be closed.

Closure involves many activities specifically conducted toprevent or mitigate undesired environmental and socialimpacts. These activities involve reclaiming disturbedareas, removing facilities, mitigating safety hazards, cross-training employees, etc.

http://www.mineralsed.ca/s/MinDevCycle.asp

EXPLORING FOR METAL

Exploring for metal

Recovery of metals from the Earth starts withexploration. Mining companies expend tremendousamounts of time, effort, and money in the search formetallic resources.

Exploration geologists must understand how metalsnaturally occur, the special geologic processes thatcontrol orebody development, and how orebodies arephysically and chemically expressed in the Earth.

Identifying deposits where geologic processes haveconcentrated sulfide minerals is a continuing challengefor exploration geologists.

They search for mineral deposits that contain richenough concentrations of metal-bearing minerals toeconomically justify mining.

Although many metallic mineral deposits have beenidentified through exploration, only a few deposits arelarge enough and have a metal content great enoughto support commercial operations. The economicallyimportant part of a mineral deposit is known as the“ore” or “orebody”.

Once an orebody is identified within a mineral deposit,geologists determine its form.

The form of the orebody is important for two reasons:the shape of an orebody helps determine the best wayto mine it, and the orebody form influences thepotential environmental impacts associated withmining.

Exploration geologists need exceptional perseverance,for they may examine dozens and dozens of mineraldeposits without finding one ore body that is rich enoughto support mining.

The exploration process begins with a geologistexamining satellite images, geologic maps, and reportsto identify areas favorable for mineral deposits.

Once these areas are defined, the geologist conductsfield examinations to create more detailed maps androck descriptions.

Geologists commonly augment their field examinationswith geochemical and geophysical explorationtechniques that help them identify specific mineraldeposits.

Traditional diamondmining inMartapura,SouthKalimantan,BorneoIsland,Indonesia.

Traditional miners panfor gold at a mine inHampalit, CentralKalimantan

How are metals recovered from the Earth?

Mineral deposits containing metals are mined from thesurface in open pit mines, or from underground.

Mining process, from the surface in open pit mines orfrom underground, separates the ores from thesurrounding rocks.

Large massive orebodies occurring at depths greaterthan about 1000 feet (350 meters) also must beextracted by expensive underground miningtechniques.

Mineral exploration is a challenging enterprise thattakes geologists to remote regions throughout theworld and requires a variety of scientific and technicalskills.

Open Pit Mining

Underground Mining

The open pit mining process includes blasting the oreloose, hauling it to a crusher, and breaking it intopieces small enough for milling.

After blasting loosens the ore and breaks it into largefragments, it is hauled to a crusher. The crusherbreaks the ore into smaller pieces, which arecommonly moved by conveyor to a mill for furtherprocessing.

Waste rock, the name for rocks and minerals thatenclose the ore and need to be removed in order torecover it, contains too few valuable minerals toprocess.

Open Pit Mining

Underground Mining

the size of the operation is much smaller than in open pit mining

very little waste rock is generated and the waste rock can be usedto fill underground areas where access is no longer needed.

Geologist at work

METAL PROCESSING

Metal Processing

Because ore is a mixture of minerals, it is necessary toseparate the minerals that contain metals from theothers.

Beneficiation is the step in the mining process thatcrushes the ore, separates, and concentrates thevaluable minerals.

Beneficiation includes milling or leaching, flotation,and the creation of a waste product called tailings.

Milling and Leaching

Large rotating mills use metal balls or rods to grind theore into tiny particles to the consistency of silt, sand,and clay.

The actual particle size can vary, but the objective is tobreak the ore into individual mineral grains.

Instead of milling, some metals mostly from certainkinds of copper and gold ores are concentrated throughthe process of leaching.

After the ore has been placed in large piles or heaps onspecially designed pads, water containing solutions ofsulfuric acid or dilute sodium cyanide is dispersedthroughout the ore leach pile.

SMELTING

The processing step called “metallurgy” furtherconcentrates the metals by separating them from theirparent minerals. The most common technique for doingthis has involved heating the minerals to a melting point.

The heating process is generally called smelting.Historically, smelting facilities, called “smelters”.

In the smelting process, the ore concentrate is mixedwith other materials known as “fluxes” and then heatedin furnaces until it melts.

As the molten metals or the metal-bearing mineralsseparate from the other materials, they accumulate inthe bottom of the furnaces and are removed.

The other constituents, primarily iron and silica, float tothe top of the furnaces. After they are removed, theycool to a solidnglassy substance called “slag”

The other significant by-products from smelting aregases, which contain suspended particles. The gasesare collected as they rise off the top of the smelterfurnaces, and they are treated to remove certainconstituents.

Sulfur dioxide gas is typically captured and convertedto sulfuric acid, which is sold as a by-product of thesmelting process.

If this much ore is mined and processed to produce onenickel and copper coin, imagine the Mineral Resourcesneeded to build a skyscraper.

ENVIRONMENTAL CONCERN

What are the major environmental concerns relatedto producing metals?

Some historic mining activities that occurred whenenvironmental consequences were poorly understoodhave left an unfortunate environmental legacy.

Mining in the early days took place at a time whenenvironmental impacts were not as well understood andmost importantly, not a matter of significant concern.

During these times, primarily before the 1970s, the miningcycle did not necessarily include closure activitiesspecifically designed to mitigate environmental or socialimpacts. As a result, historical mine sites may still haveunreclaimed areas, remnants of facilities, and untreatedwater.

Open pit mining disturbs larger areas than underground mining, andthus has larger visual and physical impacts. (Source : www.nzdl.org)

Effects on land/soil

Mining operations necessitate the removal of greenvegetation and the dumping of waste soil.

Mountains will lose their natural barriers against heavyrains with cascading flood waters eroding the top soil,making the surrounding lands ill-suited for crops andtrees, rendering them unproductive and lowlands will bevulnerable to flash floods.

Large areas may be destroyed to massive excavationsand removal of large volume of rocks and soil materials.Huge pits will be formed, destroying the aesthetic valueof the landscape.

Occurrences of landslides and mudflows due to theweakening of rocks, accumulation of sand and otherdebris in mine dams or in natural depressions maylead to great loss of life and property.

Another safety consideration at some mine sites isground sinking or “subsidence.” The ground may sinkgradually where underground workings have comeclose to the surface.

Effects on water resources

Intensive drainage or use of surface and groundwatermay cause the drying of streams or the groundwaterdischarge in springs or outlets of underground rivers.

Many mineral deposits commonly contain pyrites andother sulphuric-bearing minerals which decompose inwater and produce acid water.

Small-scale gold mining operations have beenresponsible for mercury pollution in rivers, lakes andseas.

Heat pollution results when hot waters are drawn to thesurface and are then discharged into surrounding waterbodies without initial cooling.

Effects on the communities

Dumping of tailings has affected lowland populationsliving downstream. Mine tailings fill streams or riversystems and riverbanks are periodically eroded andinundated.

Settlements in relatively lower elevations are subject tofrequent flooding, large tracts of farm lands areinundated by mine tailings during typhoons or heavyrains.

Mine tailings contain toxic substances directly inimicalto sea life and indirectly to humans.

Mine tailings caused the filling of certain bays andhave been responsible for the siltation andconsequent death of some coral reefs.

The accumulation of waste rocks and tailingoccupies large areas formerly used for agricultureand forestry purposes.

Mining expansion and pollution have dislocatedmany people from their farms, forcing them tomigrate to other areas.

Effects on air

Pollution of the air occurs during mining, smelting andrefining.

Pollution takes the form of dust , carbon monoxide(CO), sulfur dioxide (SO2), nitrogen oxides (NOx) andhydrocarbons (HC). Toxic emissions cover large areasaffecting the health of people.

Acid rain results from the interaction between sulphurdioxide emissions from smelters fed with sulphides ofcopper, lead, zinc and other metals and rainwater.

This type of pollution is responsible for the destructionof some crops and forests, the pollution of lakes andnegative effect on the health of people.

Operations and waste products associated with metalextraction and processing are the principal causes ofenvironmental concerns about metal mining.

It may Physically disturb landscapes as a result of mineworkings, waste rock and tailings disposal areas, andfacility development.

Increase the acidity of soils; such soils can be toxic tovegetation and a source of metals released to theenvironment.

Degrade surface and groundwater quality as a resultof the oxidation and dissolution of metal-bearingminerals.

Increase air-borne dust and other emissions, such assulfur dioxide and nitrogen oxides from smelters, thatcould contaminate the atmosphere and surroundingareas.

Modern mining operations actively strive to mitigatethese potential environmental consequences ofextracting metals.

Today, mining companies must plan for and deal withenvironmental impacts before, during, and aftermining

The potential environmental impacts of mining thesame type of mineral deposit can be very different indifferent locations and settings.

For example, mining in arid parts of Arizona hasdifferent potential impacts on surface water andgroundwater quality than if the same mining hadoccurred in areas of temperate climates, such as theRocky Mountains or the midwest.

How can these environmental concerns be managedand mitigated?

The key to effective mitigation lies in implementing scientificand technological advances that prevent or control undesiredenvironmental impacts.

As scientific and technological advances increase theunderstanding of the physical and chemical processes thatcause undesired environmental consequences, metal minesand related beneficiation or smelting facilities apply thisunderstanding to prevent and resolve environmentalproblems.

Ongoing mining operations and mine closure activitiesemploy several different mitigation approaches including

Reclamation of disturbed lands,

Treatments and stabilization of metal-bearing soils,

Prevention and treatment of contaminated water,

Controls on the amount and character of emissions to theatmosphere,

Minimizing waste and recycling raw materials andbyproducts.

Better, more cost-effective approaches are needed fordealing with the environmental impacts of mining,beneficiation, and smelting, especially measures thatprevent undesired environmental impacts.

Reclamation

Reclamation entails the re-establishing of viable soilsand vegetation at a mine site

It depends on adding lime or other materials that willneutralize acidity plus a cover of top soil or suitablegrowth medium to promote vegetation growth.

Modifying slopes and other surfaces and plantingvegetation as part of the process stabilizes the soilmaterial and prevents erosion and surface waterinfiltration.

Soil Treatment

High levels of metals in soils, not just acidity, can beharmful to plants, animals, and, in some cases, people.

A common approach used in dealing with contaminatedsoil is to move it to specially designed repositories.

With this approach, the volume and toxicity of the soil isnot reduced, the soil is just relocated.

Future approaches may include

Using chemical methods to stabilize metals in soils,making themless mobile and biologically available.

Using bacteriacides that stop the bacterial growththat promotes the oxidation of pyrite and theaccompanying formation of sulfuric acid.

Using bioliners, such as low permeability andcompacted manure, as barriers at the base of wastepiles.

Permanently flooding waste materials containingpyrite to cut off the source of oxygen, stop thedevelopment of acidic conditions, and preventmobilization of metals.

Water Treatment

The most common treatment for acidic and metal-bearingwaters is the addition of a neutralizing material, such aslime, to reduce the acidity.

This “active” treatment process, which causes thedissolved metals to precipitate from the water, usuallyrequires the construction of a treatment facility.

Recycling

Recycling can be an alternative source of metals thatreduces the need for new metal mines.

However, recycling facilities themselves are industrialdevelopments having their own set of environmentalimpacts.

Even though extensive and efficient recycling is animportant commitment, metal mining and production willstill be Necessary to meet society’s Demand for metals.

What is the future need and environmentaloutlook for metal mining?

The challenge for future metal production is to developenvironmentally sound mining and processing techniquesthat can also contribute to more widespread mitigation ofhistorical environmental problems.

The desire to raise global living standards, coupled with agrowing world population, will increase worldwide demandfor metals in the future.

This demand means that metal mining the industryresponsible for extracting metals from the Earth for use inour daily lives will continue to be vital and necessary.

A better scientific understanding of the environmentalimpacts of mining, coupled with great advances in miningand environmental technologies, have enabled modernminers to better predict, plan for, and prevent or minimizepotential adverse environmental impacts.

The demands for both minerals and metals, and forenvironmental protection, are expected to increase in thedecades ahead.

World population growth and rising standards of living indeveloping countries will require more minerals andmetals.

At the same time, our improved understanding of theharm that environmental degradation can cause to wildlifeand human health, is leading to higher and higherstandards of environmental protection.

SUMMARY

SUMMARY

metallic resources mined from the Earth are vital buildingblocks of our civilization and society’s need for them isincreasing.

Metallic and nonmetallic minerals occur in ordinary rocksthroughout the Earth’s crust, but only a few mineralscontain high enough concentrations of metals to be minedprofitably.

Mining cycle : exploration, extraction, mine closure.

There are two types of mining processes : Open Pitmining and Underground mining.

Beneficiation is the step in the mining process that crushesthe ore, separates, and concentrates the valuableminerals. Beneficiation includes milling or leaching,flotation, and the creation of a waste product calledtailings.

Operations and waste products associated with metalextraction and processing are the principal causes ofenvironmental concerns about metal mining.

Today, mining companies must plan for and deal withenvironmental impacts before, during, and after mining

The desire to raise global living standards, coupled with agrowing world population, will increase worldwide demandfor metals in the future.

REFERENCES

Hudson, T.L. Et al. 1999. Metal mining and theenvironment. American Geological Institute : Virginia,USA.

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