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ME551/GEO551 Geology of Industrial Minerals Spring 2007 Commodities, Part 2 Clays, Diamonds, Diatomite, Fluorite, Garnet, Graphite Reminders • What is trap rock? • Field trip to potash mines next week – – – – Monday leave at 9 AM Tues tour and return to Socorro Hotel Buckets for collecting • Term Projects? • March 20 I will not be teaching—Jim Barker • Any questions on the midterm? – Due March 9 Clays • Bentonite—Jeremy Clays—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 Types • layer silicates – layers of tetrahedral and octahedral sheets – Kaolinite, smectite, illite, chlorite, vermiculite • the metal oxides and hydroxides and oxy-oxides – gibsite • amorphous and allophanes – structurally disordered aluminosilicates – Allophane, Imogolite Clays—definition • particle size of less than 2 micrometers • family of minerals • rock term Clays—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—properties • • • • • • Color plasticity mineral composition absorption qualities firing characteristics clarification properties d e p e n d e n t . Properties—charge sources I • Two main sources of charge in clay n minerals are isomorphous a substitution and pH-dependent charges. l l o p h a n e s , http://jan.ucc.nau.edu/doetqp/courses/env320/lec12/Lec12.html Charge 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 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. • In the metal oxides acid soils tend to develop positive charges because of the protonation of the oh ggoud on the oxide surfaces. Clay—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—uses • Burn to a light color and accepts glaze, plastic • 35% floor and wall tile • 22% sanitaryware • 43% other uses Bentonite—uses • Clay consisting of smectites Common clay—uses • • • • 56% brick 20% cement 16% lightweight aggregate 8% other uses (fillers and extenders) Fire clay—uses • 73% refractories • 27% other uses Fuller’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 • 75% absorbent uses • 25% other uses Kaolin—uses • Near white containing kaolinite • 55% paper • 7% refractories • 38% other uses Kaolin—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 Kaolin Clays—substitutions • Limited substitutions possible • calcium carbonate • talc Clays—production – ball clay – common clay: various – fire clay – fuller’s earth: U.S., Germany – kaolin: U.S., Uzbekistan, Czech Republic, United Kingdom, Brazil Clays—geology • soil horizons • continental and marine sediments • geothermal fields • volcanic deposits • weathering rock formations • coal beds Bricks—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—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—clay • Open pits • organic emissions (EPA developing standards, MACT) • impoundment of slimes • dust control Colin C. Harvey, 1999 Diamonds Diamonds • Greek adamas meaning invincible • Used in India 2,500 yrs ago Diamonds—introduction • clarity, color, shape, size is used as industrial-grade diamond (nongem) http://www.brysonburke.com/diamonds_find_the_source.html Diamonds—properties • Hardest substance known • highest thermal conductivity • chemical stability • optical properties • refract light atomic connectivity of the carbon atoms gives the gem its hardness Diamonds—production Diamonds—uses • • • • • • • • • • Middle Ages--healing powers Grinding drilling cutting polishing abrasive wear- and corrosion-resistant coatings, special lenses heat sinks in electrical circuits wire drawing Diamonds—substitutions • • • • cubic boron nitride silicon nitride but diamond is more than twice as hard synthetic diamonds (US) Diamonds—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 minerals • • • • • • ilmenite titanium and magnesium rich chromite chrome diopside magnesium rich olivine pyrope garnets eclogitic garnets Carat • 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) Price Mining Alluvial mining by traditional methods continues, as seen here in Sierra Leone. Mining Diamonds—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 Diatomite Diatomite—introduction • made of plant fossils shaped like soda straws • silica • looks like chalk (CaCO3) • diatomaceous earth Diatomite http://www.rockdetective.org/f... Diatomite http://www.maidenwell.com/ Chemical composition • • • • 86% silica 5% sodium 3% magnesium 2% iron Diatomite—properties • Light weight (hollow fossil shells) • does not conduct heat Diatomite—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—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—production Diatomite—geology • Saltwater – contains a high crystalline silica content • Fresh water lake – dry lakebeds and is characteristically low in crystalline silica content Diatomaceous earth http://www.minerals.epcorp.com.. Dredging is one mining method http://www.hi.is/HI/Stofn/Myva... Safety • 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 Fluorite Fluorite • Latin fluo, meaning flow Fluorite—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) Fluorite—properties • fluorospar • ability as a flux • ore of F Fluorite—uses • • • • • • flux in steel and aluminum processing in the preparation of glasses and enamels manufacture of hydrofluoric acid for carved ornamental objects fluorinated water gemstone Fluorite http://mineral.galleries.com/minerals/halides/fluorite/fluorite.htm Fluorite—substitutions • Olivine • dolomitic limestone • Byproduct fluorosilicic acid Fluorite—production Fluorite—geology • • • • • Rio Grande Rift (RGR) deposits Mississippi Valley type (MVT) deposits Sedimentary stratiform deposits volcanic massive sulfide deposits gangue in epithermal and mesothermal veins Garnet Garnet • 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—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—introduction • aluminum garnets – almandine or almandite – pyrope – grossularite – spessartite • iron garnets – andradite • chromium – uvarovite Garnet—properties • • • • • Various colors isometric specific gravity 3-4 Luster is vitreous Hardness is 6.5 - 7.5 Almandine Andradite http://en.wikipedia.org/wiki/Garnet Garnet—uses • • • • • waterjet cutting, 35% abrasive blasting media, 30% water filtration, 15% abrasive powders, 10% other end uses, 10% Garnet—substitutions • • • • natural and manufactured abrasives Ilmenite magnetite plastics Garnet—production Garnet—geology • Gneisses and schists • contact-metamorphic deposits in crystalline limestones • pegmatites • igneous rocks • serpentinites • vein deposits • alluvial garnet Graphite Graphite • Greek (graphein): to draw/write • for its use in pencils Graphite—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 History • 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—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 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. Mineralogy Graphite 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 Graphite http://www.phy.mtu.edu/faculty/info/jaszczak/borrowdale.html Graphite—uses • Refractory applications 45% (brick and linings) • brake linings 20% • lubricants, 5% • dressings and molds in foundry operations, 5% • other uses 25% END-USES Main uses are in refractors, lubricants, brake linings, foundry moulds, and electrodes. Nontraditional applications include expanded graphite and graphite foils (a thin graphite cloth). Uses of natural graphite in 2004 refractory applications 24% Graphite Foils brake linings 46% foundry operations 13% 8% 9% lubricants steelmaking and other uses (pencils, battery...) Graphite Packing Expanded Graphite Graphite—substitutions • • • • • graphite powder scrap from discarded machined shapes calcined petroleum coke Molybdenum disulfide Finely ground coke with olivine Graphite—production Graphite—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. Geology Flake 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 Geology 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. Source - http://www.asbury.com 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 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 nongraphitic 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 Method Graphite 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. Primary Crusher Mill Flotation Cells Dryers 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.