ME551/GEO551 Geology of Industrial Minerals Spring 2011

ME551/GEO551 Geology of ME551/GEO551 Geology of Industrial Minerals Industrial Minerals

Spring 2011Spring 2011

Commodities, Part 2

Bauxite, Clays, Diamonds, Diatomite, Feldspar, Fluorite, Garnet, Graphite

RemindersReminders

• SME discussion• Research Projects? (25% grade)

– Soil/stream sediment survey in Lemitar carbonatites for REE using PXRF

– Lesson plans• Any questions on the midterm?

– Due March 22

Bauxite

Bauxite

• Al is 3rd most abundant mineral but never found in it’s native state

• Aluminum ore, most commonly formed in deeply weathered rocks—laterites.

• A common residual or transported constituent of clay deposits in tropical and subtropical regions.

• Composed of a mixture of various aluminium oxides and hydroxides (principally gibbsite (Al(OH)3), boehmite (AlO(OH)), and diaspore (AlO(OH))).

Bauxite

• Bauxite is a product of near-surface alteration of aluminous rocks, creating a zone depleted of Fe and Si and enriched in Al bearing minerals.

• Typical analysis of bauxite:– ~50% Al2O3– ~5% SiO2– 15% Fe2O3– 3% TiO2 (Anatase)

• It is THE raw material for ALL primary aluminum.

Introduction

First discovered by les Baux, France 1821

The first commercial extraction of alumina (Al2O3) from bauxite has been attributed to Henri Sainte-Claire Deville in about 1854

Bauxites: soft/friable, variable textures, colors, sizes

Types

• Not all bauxites are equal

• Can be divided “generally” into• three types:

• – Gibbsitic Al(OH)3 ; Low Temp

• – Boehmitic, >4% AlO(OH) ; Hi Temp

• – Diasporic, >5% AlO(OH) ; Very Hi Temp

What makes a good deposit?

• Proximity to processing plant or infrastructure to export.

• – Low extraction costs

• – Quality:– • High % extractible Al2O3 – • Low % reactive SiO2

Uses

• Blast Furnaces• Iron/Steel Ladles• Electric Arc

furnaces• Tundishes• Soaking Pits• Open Hearth• Cement• Aluminum

Ghana Bauxite Company Ltd- Awaso

Ghana Bauxite Company Ltd- Awaso

MiningMining

• Eighty percent of world bauxite production is from surface minesEighty percent of world bauxite production is from surface mines

• Southern Europe and Hungary, produce from underground Southern Europe and Hungary, produce from underground excavations excavations

• Some surface deposits has no overburden, and on others, the bauxite Some surface deposits has no overburden, and on others, the bauxite may be covered by 70 meters or more of rock and clay may be covered by 70 meters or more of rock and clay

• Deposits that are hardened may require blasting in order to release the Deposits that are hardened may require blasting in order to release the ore ore

• Once the bauxite is loosened into manageable pieces it is generally Once the bauxite is loosened into manageable pieces it is generally loaded into trucks or railroad cars and transported to crushing or loaded into trucks or railroad cars and transported to crushing or washing plants or to stockpiles washing plants or to stockpiles

CBG, GUINEA BAUXITE (ALUMINIUM ORE) MINING OPERATIONS, GUINEAhttp://www.mining-technology.com/projects/cbg/

Production

Production

Bauxite—Geology

• tropical weathering of underlying, aluminium-rich rock

• weathering that forms under conditions of high rainfall, high mean temperature, good drainage, but modest relief and no erosion

• grades in Guinea range 40-60% Al2O3

Geologic Description and Distribution

Geological definition of bauxite

Classification of bauxites, ferrites and transitional rocks. (Schellman 1983).

Minerals common to bauxite deposits


Schematic Bauxite Profile


Bauxite Distribution

•Tropical regions: high T (avg 22°), rainfall (1.2 m);

•SiO2 leached in dry season, Fe2O3, Al2O3 formedduring wet season

Bauxite—Processing

• The first commercial extraction of alumina (Al2O3) from bauxite has been attributed to Henri Sainte-Claire Deville in about 1854.

• Crushing, cleaning/washing and drying

The Bayer Process, which continues to be the most economical method of manufacturing alumina can be schematically summarised in a flow charthttp://chemsrv.uwimona.edu.jm:1104/lectures/bauxite.html

Bayer Process• mining • dissolution of the alumina at elevated

temperatures • addition of flocculants • precipitation of pure Gibbsite • regeneration of the solutions for recycling • heating the Gibbsite to 1100C (calcination)

to give alumina

Bauxite—Substitutes

• Anorthosite

• alunite

• coal wastes

• oil shales

• clay

• silicon carbide

• alumina-zirconia

ClaysClays—Introduction—Introduction

ClaysClays—Introduction—Introduction• Stone age• Types

– ball clay (primarily of kaolinite with illite, chlorite, smectite minerals, quartz)

– bentonite (smectite with feldspars, biotite, quartz)

– common clay (illite and chlorite, others)

– fire clay (kaolinite, halloysite, diaspore)

– fuller’s earth (attapulgite, montmorillonite)

– kaolin

TypesTypes

• layer silicates– layers of tetrahedral and octahedral sheets – Kaolinite, smectite, illite, chlorite, vermiculite– Rich in Al, Si, and water

• the metal oxides and hydroxides and oxy-oxides– gibsite

• amorphous and allophanes– structurally disordered aluminosilicates – Allophane, Imogolite

ClaysClays—definition—definition

• particle size of less than 2 micrometers

• family of minerals

• rock term

Clays—propertiesClays—properties

• chemical composition

• layered structure

• size

• great affinity for water (double in thickness when wet)

• soak up ions, release the ions later when conditions change

Clays—propertiesClays—properties

• When clays become wet, they become plastic• When clays are fired they become hard• Color• plasticity• mineral composition• absorption qualities• firing characteristics• clarification properties

Charge propertiesCharge properties

• Charge development of on silicate clays is mainly due to isomorphous substitution.

• This is the substitution of one element for another in ionic crystals with out change of the structure.

• It takes place during crystallization and is not subject to change afterwards.

• It takes places only between ions differing by less than about 10% to 15% in crystal radii.

• In tetrahedral coordination, Al3+ for Si4+ and in octahedral coordination Mg2+, Fe2+, Fe3+ for Al3+.

• Charges developed as a result of isomorphous substitution are permanent and not pH-dependent.

Charge propertiesCharge properties

• In allophanes, some silicate clays e.g. kaolinite, and the metal oxides the main source of charge are termed pH -dependent charges because these charges depend on the pH of the soil.

• pH depend charges are variable and may either be positive or negative depending on the pH of the soil.

Clay—usesClay—uses• Ceramics

• fillers and extenders

• construction (hydraulic cement, structural clay products, aggregates)

• drilling mud

• fiberglass

• Iron Ore Pelletizing

• paper

• carrier to mix paint and color pigment

Ball clay—usesBall clay—uses

• Burn to a light color and accepts glaze, plastic

• Added to other clays to improve their plasticity

• 35% floor and wall tile• 22% sanitary ware• 43% other uses

Bentonite—uses• Clay consisting of smectites• Formed from alteration of volcanic ash

• Made up mainly of montmorillinite, (Na,Ca)0.33(Al,Mg)2(Si4O10)

(OH)2·nH2O

• Named for Fort Benton, WY, where it was first described as part of a Cretaceous tuff sequence

• 26% pet waste absorbent• 25% foundry sand bond• 19% drilling mud• 15% iron ore pelletizing• 15% other uses

End Use Statistics(USGS 2005)

Properties & Applications

• Thixotropy– Can be semi-solid at rest, but

will be liquid when agitated– Used as a thickening and suspension agent in

paints, dyes, and varnishes

(KSGS 2002)

Properties & Applications

• Absorption / Adsorption– Can absorb several times it dry weight in water– Pet litter, impermeable clay liners, wastewater

treatment, detergent purification, paper pulp purification, de-inking

(IMA-NA 2007)

Bentonite as a Value-Added Commodity

• Bentonite is not often taken straight from the ground to market.

• Much purification is often undergone to specialize the product– Sieving (for granular bentonite)

– Milling (fine and superfine powdered bentonite)

– Removal of associated gangue minerals

– Treated with acids (“bleaching earths”)

– Treated with organics (“organoclays”)

(IMA-NA 2007)

Common clay—usesCommon clay—uses

• 56% brick

• 20% cement

• 16% lightweight aggregate

• 8% other uses (fillers and extenders)

Fire clay—usesFire clay—uses

• Resistant to heat (refractory)

• 73% refractories

• 27% other uses

Fuller’s earth—usesFuller’s earth—uses

• mineral substance characterized by the property of absorbing basic colors and removing them from oils

• fulling of wool to remove oil and grease• Absorbants • Pesticides

• 75% absorbent uses• 25% other uses

Kaolin—usesKaolin—uses

• Near white containing kaolinite

• 55% paper

• 7% refractories

• 38% other uses

Kaolin—usesKaolin—uses

• mildew-resistant latex paints• vinyl wire insulation• printing inks• Cosmetics• rubber tires• fiberglass and nylon• auto and truck body components • production of medicines• ceramics• catalysts for petroleum refining• extenders for fertilizers, pesticides, and herbicides

KaolinKaolin

Clays—substitutionsClays—substitutions

• Limited substitutions possible

• calcium carbonate

• talc

Clays—productionClays—production

– ball clay– common clay: various– fire clay– fuller’s earth: U.S., Germany– kaolin: U.S., Uzbekistan, Czech Republic,

United Kingdom, Brazil

Production Methods

• Drilling & Sampling• Soil Profiling (to aid in

speedy recovery after reclamation)

• Topsoil & Overburden removal (usual with scrapers)

• Quarrying with loader & truck

• Only economic to mine bentonite with no more than 50 feet of overburden

(WMA-Minelife 2007)

Simplified Bentonite Mill Flow-Chart

(WMA Minelife, 2007)

USGS Commodities SummaryUSGS Commodities Summary


Clays—geologyClays—geology

• soil horizons• continental and marine sediments

• geothermal fields

• volcanic deposits

• weathering rock formations

• coal beds

Bricks—processingBricks—processing

• Common clay used to make bricks

• formed or shaped either by extrusion– involves forming a column of clay by

pushing the material through a die at high pressure.

– then cut into bricks (known as 'wirecut')– drainage pipes and clay roof tiles made

similar process

Bricks—processingBricks—processing

• or the 'soft-mud' process– individual bricks are formed in a sand-lined

mould from a clay with a relatively high moisture content (known as 'stock' bricks)

– dried prior to firing– fired using natural gas in a linear kiln

known as a 'tunnel kiln’– 1050–1100°C

Environmental considerations—clayEnvironmental considerations—clay

• Open pits

• organic emissions (EPA developing standards, MACT)

• impoundment of slimes

• dust control

Colin C. Harvey, 1999

DiamondsDiamonds

DiamondsDiamonds

• Greek adamas meaning invincible

• Used in India 2,500 yrs ago

• Most popular gemstone

Diamonds—introductionDiamonds—introduction

• clarity, color, shape, size is used to determine industrial-grade diamond (nongem)

http://www.brysonburke.com/diamonds_find_the_source.html

Diamonds—propertiesDiamonds—properties

• Hardest substance known• highest thermal conductivity• chemical stability• optical properties• refract light

atomic connectivity of the carbon atoms gives thegem its hardness

Diamonds—productionDiamonds—production



Diamonds—usesDiamonds—uses• Middle Ages--healing

powers• Grinding• Drilling • Cutting • Polishing • Abrasives • Wear- and corrosion-

resistant coatings • Special lenses

• Heat sinks in electrical circuits

• Wire drawing• Diamond windows• Heat sinks• Low friction

microbearings• Wear-resistant parts

Diamonds—substitutionsDiamonds—substitutions

• cubic boron nitride

• silicon nitride

• but diamond is more than twice as hard

• synthetic diamonds (US)

Diamonds—geologyDiamonds—geology

• Kimberlites

• lamprorites

• alluvial (placer) deposits for these rocks

• molten rock from 75 to 120 miles below the earth's surface 40 kbar and 900° C

The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit

http://en.wikipedia.org/wiki/Diamond

Schematic diagram of a volcanic pipe http://en.wikipedia.org/wiki/Diamond

Indicator mineralsIndicator minerals

• ilmenite

• titanium and magnesium rich chromite

• chrome diopside

• magnesium rich olivine

• pyrope garnets

• eclogitic garnets

CaratCarat

• carat weight measures the mass of a diamond

• One carat is defined as a fifth of a gram

• 200 milligrams

• approximately 0.007 ounce

• point unit—equal to one one-hundredth of a carat (0.01 carat, or 2 mg)

PricePrice

Mining

• Artisanal mining

• Hard rock mining (underground)

• Marine mining

• Open pit or open-cast mining

• Placer mining

MiningMining

Alluvial or artisanal mining by traditional methods continues, as seen here in Sierra Leone.

MiningMining

Diamonds—processingDiamonds—processing

• Crush

• scrubbers and degritting and sanding sections remove fine waste material for disposal

• Heavy-medium separation or grease belts

• X-ray fluorescence sorters are used to extract the diamonds

Conflict minerals

• What are “Blood diamonds”

Conflict minerals

• “blood diamonds”– Profits from the sale

of diamonds fuels the oppression and in some cases slaughter of thousands of people

– Funds rebels and terrorists

DiatomiteDiatomite

Diatomite—introductionDiatomite—introduction

• made of plant fossils shaped like soda straws

• silica

• looks like chalk (CaCO3)

• diatomaceous earth

DiatomiteDiatomite

http://www.rockdetective.org/f...

DiatomiteDiatomite

http://www.maidenwell.com/

Chemical compositionChemical composition

• 86% silica

• 5% sodium

• 3% magnesium

• 2% iron

Diatomite—propertiesDiatomite—properties

• Light weight (hollow fossil shells)

• does not conduct heat

Diatomite—usesDiatomite—uses

• Once used in dynamite• insulate steam pipes• filtration aid (swimming pools)• mild abrasive• mechanical insecticide (physico-sorptive

properties)• absorbent for liquids• Cat litter• activator in blood clotting studies• thermal insulator • plants

Diatomite—substitutionsDiatomite—substitutions

• Expanded perlite• silica sand• talc• ground silica sand,• ground mica• clay• exfoliated

vermiculite

• Perlite• vermiculite• ground limestone• various clays• special brick• mineral wool• expanded perlite

Diatomite—productionDiatomite—production



Diatomite—geologyDiatomite—geology

• Saltwater – contains a high crystalline silica content

• Fresh water lake– dry lakebeds and is characteristically low in

crystalline silica content

Diatomaceous earthDiatomaceous earth

http://www.minerals.epcorp.com..

Dredging is one mining methodDredging is one mining method

http://www.hi.is/HI/Stofn/Myva...

SafetySafety

• drying of the hands, if handled without gloves

• highly crystalline form of silica, resulting in sharp edges

• dangerous to breathe and a dust mask is recommended when working with it

• silicosis

Feldspar and nepheline syenite—introduction


• More than 20 minerals– albite– oligoclase– andesine– labradorite– bytownite– anorthite– microcline– sanidine– orthoclase


• low symmetry, being only monoclinic

• twin easily

• dull to rarely vitreous luster

• blocky crystals

• two directions of cleavage at nearly right angles

• XAl(1-2) Si(3-2) O8 – X is Na, Ca, K

Feldspar—introduction

• Feld from field

• spar meaning easily cleaved material

• most common minerals in the Earth's crust

Identification

Nepheline syenite

• light-colored, silica-deficient feldspathic igneous rock

• sodium and potassium feldspars

• nepheline, no quartz

• not mined in US but in Canada

Feldspar and nepheline syenite—properties

• In glass, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion

• in ceramics, feldspar is used as a flux, melting at an early stage in the firing process and forming a glassy matrix that bonds together the other components of the system

Feldspar and nepheline syenite—uses

• Dimension stone

• Ceramics 55% of total world demand

• glass 35% of world demand– container– flat glass – insulation-grade fibreglass

Nepheline syenite

• alumina acts as a matrix of stabilizser, enhancing the workability of molten glass, and increasing the resistance for scratching, breaking and chemical protection

• alkali acts as a flux agent, lowering the melting temperature of the batch (no need for soda ash)

Feldspar and nepheline syenite—substitutions

• feldspar-silica mixtures

• clays

• talc

• pyrophyllite

• spodumene

• electric-furnace slag

• nepheline syenite

Feldspar—production



Feldspar and nepheline syenite—geology

• China• France• Italy• Thailand• Turkey • USA• Canada

65 % of the production

Feldspar and nepheline syenite—procssing

• Crush

• screen

• magnetic separation

• air classify

• refined ore

Specifications for glass

http://www.fineton.com/new_page_6.htm#The Nepheline Syenite for Glass Industry

Fluorite/fluorsparFluorite/fluorspar

FluoriteFluorite

• Latin fluo, meaning flow

FluoriteFluorite—introduction—introduction• CaF2, Calcium Fluoride• halide• variable color• Luster is vitreous.• transparent to translucent.• Cleavage is perfect in 4 directions forming octahedrons.• Hardness is 4 • Fracture is irregular and brittle. • Specific Gravity is 3.1+ (heavy)

FluoriteFluorite—properties—properties

• fluorospar

• ability as a flux

• ore of F

FluoriteFluorite—uses—uses

• flux in steel, ceramics and aluminum processing• in the preparation of glasses and enamels • manufacture of hydrofluoric acid (electroplating,

stainless steel, refrigerant, plastics)• for carved ornamental objects• fluorinated water• gemstone

FluoriteFluorite

http://mineral.galleries.com/minerals/halides/fluorite/fluorite.htm

FluoriteFluorite—substitutions—substitutions

• Olivine

• dolomitic limestone

• Byproduct fluorosilicic acid

FluoriteFluorite—production—production



FluoriteFluorite—geology—geology

• Rio Grande Rift (RGR) deposits

• Mississippi Valley type (MVT) deposits

• Sedimentary stratiform deposits

• volcanic massive sulfide deposits

• gangue in epithermal and mesothermal veins

GarnetGarnet

GarnetGarnet

• Latin granatus (“grain")

• possibly a reference to the Punica granatum ("pomegranate"), a plant with red seeds similar in shape, size, and color to some garnet crystals

Garnet—introductionGarnet—introduction

• group of complex silicate minerals with similar crystalline structures

• A3B2(SiO4)3, where A can be Ca, Mg, Fe, Mn; B can be Al, Cr, Fe, Ti

Garnet—introductionGarnet—introduction

• aluminum garnets– almandine or almandite– pyrope– grossularite– spessartite

• iron garnets– andradite

• chromium– uvarovite

Garnet—propertiesGarnet—properties

• Various colors

• isometric

• specific gravity 3-4

• Luster is vitreous

• Hardness is 6.5 - 7.5

http://en.wikipedia.org/wiki/GarnetAndradite

Almandine

Garnet—usesGarnet—uses

• waterjet cutting, 35%

• abrasive blasting media, 30%

• water filtration, 15%

• abrasive powders, 10%

• other end uses, 10%

Garnet—substitutionsGarnet—substitutions

• natural and manufactured abrasives

• Ilmenite

• magnetite

• plastics

Garnet—productionGarnet—production



Garnet—geologyGarnet—geology

• Gneisses and schists• contact-metamorphic deposits in crystalline

limestones• pegmatites• igneous rocks• serpentinites• vein deposits• alluvial garnet

GraphiteGraphite

GraphiteGraphite

• Greek (graphein): to draw/write

• for its use in pencils

Graphite—introductionGraphite—introduction

• C

• confused with molybdenite, which is denser and has a silver blue streak

• gray streak

• Luster is metallic to dull

• Cleavage is perfect in one direction

HistoryHistory

• First use of graphite: primitive man to make drawings, and by Egyptians to decorate pottery.

• Graphite processing: 1400 AD in the Haffnerzell District of Bavaria.

• Through the Middle Ages graphite was confused with galena and Molybdenite.

• First names: Plumbago (lead -silver) & black lead

• Discovered: 1565 by Gessner (recognized as a mineral), but its composition was determined in 1779 by Scheele.

Graphite—propertiesGraphite—properties• Milled, drilled and turned in a lathe to a desired shape • Making Brushes• conductive• chemically stable• high strength• hardness 1-2• specific gravity 2.2• good conductor of electricity• lubricant

Physical CharacteristicsPhysical Characteristics• Color is dark gray, black, or black silver. • Luster is metallic to dull. • Transparency crystals are opaque • Crystal System is hexagonal • Hardness is 1 - 2 • Specific Gravity 2.2 • Cleavage is perfect in one direction. • Fracture is flaky. • Streak is black gray to brownish gray. • Melting Point of 3,500ºC.• Graphite is an excellent conductor of heat and electricity. • Other Characteristics: thin flakes are flexible but inelastic, mineral

can leave black marks on hands and paper.• Best Field Indicators are softness, luster, density and streak.

MineralogyMineralogyGraphite is a native element composed only of carbon. It has the same composition as diamond, however it has very different structures.

•Diamond crystallizes in the Isometric system X graphite crystallizes in the hexagonal system.

Source- http://www.chem.ox.ac.uk/icl/heyes/structure_of_solids/Lecture1/Lec1.html

GraphiteGraphite

http://www.phy.mtu.edu/faculty/info/jaszczak/borrowdale.html

Graphite—usesGraphite—uses

• Refractory applications 45% (brick and linings)

• brake linings 20%

• lubricants, 5%

• dressings and molds in foundry operations, 5%

• other uses 25%

END-USESEND-USESMain uses are in refractors, lubricants, brake linings, foundry moulds, and electrodes. Non-traditional applications include expanded graphite and graphite foils (a thin graphite cloth).

Graphite Foils

Graphite Packing Expanded Graphite

Uses of natural graphite in 2004

13%

24%

8%9%

46%

refractory applications

brake linings

foundry operations

lubricants

steelmaking and other uses(pencils, battery...)

Graphite—substitutionsGraphite—substitutions

• graphite powder

• scrap from discarded machined shapes

• calcined petroleum coke

• Molybdenum disulfide

• Finely ground coke with olivine

Graphite—productionGraphite—production



Graphite—geologyGraphite—geology

Types of Natural Graphite :

Disseminated flake

Crystalline vein (lump or high crystalline graphite)

Amorphous

Graphite occurs in many types of igneous, sedimentary & metamorphic rocks. The more important are those found in metasomatic –hydrothermal deposits, & in sedimentary rocks that have been subjected to regional or thermal metamorphism.

Associated Minerals include quartz, calcite, micas, iron meteorites, and tourmalines.

GeologyGeologyFlake graphite:• is found in metamorphic rocks uniformly distributed through the ore

body or in concentrated lens shaped pockets. • Graphite flake occurs as a scaly or lamella form in certain metamorphic

rocks such as limestone, gneisses and schists. • Carbon concentrations vary between 5% and 40%. • Flake graphite occurs in most parts of the world. Notable deposits are

Canada, Brazil, Madagascar, Australia, USA(Texas-1980, Alabama &Pennsylvania-1960’s), Germany

• Flake: marble, gneiss, and schist (most common rock types)

Source -http://www.alibaba.com/catalog/10876290/Natural_Flake_Graphite.html

Crystalline vein graphite:• is believed to originate from crude oil deposits that through time,

temperature and pressure have converted to graphite. • Vein graphite is found along the intrusive contacts of pegmatites

with limestone. • The vein fissures are typically between 1cm and 1 m thick, and are

normally > 90% pure. • Although this form of graphite is found all over the world, it is only

commercially mined in Sri Lanka.

GeologyGeology

Source - http://www.asbury.com

Geology Geology Amorphous graphite: • Amorphous graphite is found as minute particles in beds of

mesomorphic rocks such as coal, slate or shale deposits. • The graphite content ranges from 25% to 85% dependent on the

geological conditions. • Most of the amorphous deposits with economic importance are

formed by metamorphism of coal or carbon rich sediments. • Notable occurrences are in Mexico, North Korea, South Korea and

Austria.

Source - http://kuroko.mus.akita-u.ac.jp/sampimag/11767e.htm

Artificial GraphiteArtificial Graphite

• Synthetic graphite can be produced from coke and pitch.

• Synthetic Graphite consists mainly of graphitic carbon that has been obtained by graphitisation, heat treatment of non-graphitic carbon, or by chemical vapour deposition from hydrocarbons at temperatures above 2100K .

• Synthetic Graphite tends to be of higher purity though not as crystalline as natural graphite.

• On the whole, synthetic graphite tends to be of a lower density, higher porosity and higher electrical resistance.

• Its increased porosity makes it unsuitable for refractory applications.

Source - http://www.intertrade.com.

Mining MethodMining MethodGraphite is commonly extracted through open-pit methods. In some cases, it has been extracted through underground mining (vein deposits in Sri Lanka).

Mining - Graphite ore is extracted with the use of shovels & bulldozers that load dump trucks with the crude ore.

Mechanical concentration - The ore is crushed by a primary crusher and then submitted to a series of roll crushers and classifiers to remove the oversizes and gangue. Flotation is used for the mechanical separation of the graphite from impurities present in the ore. The cycle mill-flotation is repeated until a grade between 87 -96% of carbon is reached.

Chemical concentration - Concentration with the use of chemical agents is used to remove impurities that remain in the graphite after the mechanical concentration process. Some firms make high purity graphite (98% - 99%carbon) by leaching concentrate with strong acids or alkalis.

Primary Crusher

Mill

Flotation Cells

Dryers

Read the following sections in the Read the following sections in the IM text.IM text.

• Chromite

• Gypsum

• Helium

• Iodine

• iron ore

• Kyanite

• lithium

Documents

ME551/GEO551 Geology of Industrial Minerals Spring 2011