ME551/GEO551 Geology of Industrial Minerals Spring 2011

1. ME551/GEO551 Geology of Industrial Minerals Spring 2011 Commodities, Part 2 Bauxite, Clays, Diamonds, Diatomite, Feldspar, Fluorite, Garnet, Graphite

2. Reminders • 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

3. Bauxite

4. 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))).

5. 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.

6. 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

7. 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

8. What makes a good deposit? • Proximity to processing plant or infrastructure to export. • – Low extraction costs • – Quality: • • High % extractible Al2O3 • • Low % reactive SiO2

9. Uses • Blast Furnaces • Iron/Steel Ladles • Electric Arc furnaces • Tundishes • Soaking Pits • Open Hearth • Cement • Aluminum Ghana Bauxite Company Ltd- Awaso

10. Mining • Eighty percent of world bauxite production is from surface mines • Southern Europe and Hungary, produce from underground excavations • Some surface deposits has no overburden, and on others, the bauxite may be covered by 70 meters or more of rock and clay • Deposits that are hardened may require blasting in order to release the ore • Once the bauxite is loosened into manageable pieces it is generally loaded into trucks or railroad cars and transported to crushing or washing plants or to stockpiles Ghana Bauxite Company Ltd- Awaso

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

12. Production

13. Production

14. 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

15. Geologic Description and Distribution Geological definition of bauxite Classification of bauxites, ferrites and transitional rocks. (Schellman 1983).

16. Minerals common to bauxite deposits

17. Geologic Description and Distribution Schematic Bauxite Profile

18. Geologic Description and Distribution Bauxite Distribution •Tropical regions: high T (avg 22°), rainfall (1.2 m); •SiO2 leached in dry season, Fe2O3, Al2O3 formed during wet season

19. 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

20. 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

21. 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

22. Bauxite—Substitutes • Anorthosite • alunite • coal wastes • oil shales • clay • silicon carbide • alumina-zirconia

23. Clays—Introduction

24. 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

25. Types • 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

26. Clays—definition • particle size of less than 2 micrometers • family of minerals • rock term

27. 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

28. Clays—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

29. 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.

30. 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.

31. 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

32. Ball 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

33. 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

34. End Use Statistics (USGS 2005)

35. 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)

36. 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)

37. 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)

38. Common clay—uses • 56% brick • 20% cement • 16% lightweight aggregate • 8% other uses (fillers and extenders)

39. Fire clay—uses • Resistant to heat (refractory) • 73% refractories • 27% other uses

40. 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 • Absorbants • Pesticides • 75% absorbent uses • 25% other uses

41. Kaolin—uses • Near white containing kaolinite • 55% paper • 7% refractories • 38% other uses

42. 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

43. Kaolin

44. Clays—substitutions • Limited substitutions possible • calcium carbonate • talc

45. Clays—production • ball clay • common clay: various • fire clay • fuller’s earth: U.S., Germany • kaolin: U.S., Uzbekistan, Czech Republic, United Kingdom, Brazil

46. 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)

47. Simplified Bentonite Mill Flow-Chart (WMA Minelife, 2007)

48. USGS Commodities Summary

49. USGS Commodities Summary

50. Clays—geology • soil horizons • continental and marine sediments • geothermal fields • volcanic deposits • weathering rock formations • coal beds