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The market for titanium feedstocks (ilmenite, rutile,synthetic rutile and slag) is driven primarily by offtake from the titanium dioxide (TiO2) pigment industry. The pigment sector depends on the performance of the global economy. Titanium sponge is the first stage of titanium metal manufacture. It constitutes a minor component (3 percent) of overall demand for titanium feed-stocks. Production and consumption TiO2 pigment consumption in 2004 was estimated to be 4.63 Mt (5.1 million st), up 7.6 percent from 2003. It was driven by strong demand in most regions. In the United States, apparent TiO2 pigment consumption rebounded by 5.4 percent (highest growth rate since 1997) to an estimated 1.12 Mt (1.23 million st), following the decrease in demand during 2003. Chinese TiO2 pigment consumption continued its strong upward trend, increasing by 10 percent to 598 kt (659,000 st) in 2004.

Jan 1, 2005

By E. Milosavljevic, C. H. Bucknam, K. L. Gabby, T. C. Eisele

"Since mercury is chemically similar to silver, it tends to dissolve along with the silver and gold during cyanide leaching. Ultimately, mercury is recovered along with the silver as mercury/silver/gold amalgam, which requires retorting to remove the mercury prior to refining the silver and gold. A possible approach to separating mercury from silver and gold in cyanide leach solutions is to take advantage of the replacement reaction between [Hg(CN)4]2- and Ag2S, which results in precipitation of mercury as HgS while dissolving silver as [Ag(CN)2]-. Results are presented demonstrating that mercury can be removed from cyanide solutions with high effectiveness while, at the same time, recovering additional silver in solution. Initial experiments with static flasks in the laboratory showed a high degree of mercury removal could be achieved. Results using actual metallurgical plant products in bottle roll tests indicate the process works on a larger scale, but also results in significant gold losses if the solution being treated has high gold levels, such as carbon stripping pregnant eluent solution. IntroductionThe dissolution of mercury along with precious metals during cyanide leaching is a long-standing problem, which can result in significant mercury toxicity issues (Washburn, 2003). Mercury is first dissolved by the cyanide solution, and then, since it has a great deal of chemical similarity to silver, it follows silver throughout the concentration and recovery processes, ultimately being recovered as a silver/ mercury amalgam when the metal is precipitated by either the Merrill-Crowe process or by electrowinning.While it would be desirable to either prevent mercury dissolution entirely while still allowing silver dissolution, or to selectively capture mercury before the precious-metals recovery step, there is not yet an effective and economically practical approach to doing this (Grosse, 2003; Ravichandran, 2004; Misra, 1998; Pai, 2000). There are a few processes that have been proposed, such as differential adsorption. While activated carbon, as used in the carbon-in-pulp process, is not highly selective between mercury and silver (Washburn, 2003), it may be possible to achieve some separation by selective elution of the carbon to produce high-mercury and low-mercury eluates (Bunney et al., 2010). Certain synthetic resins were shown to be selective for gold but are more expensive than carbon, requiring special equipment, and have not yet been shown to be selective for mercury (Grosse, 2003). There may be potential for differential dissolution approaches, as thiosulfate leaching does not dissolve mercury sulfides as readily as it dissolves gold (Oraby et al., 2010), and it is possible that it may be similarly more selective for dissolving silver relative to mercury. Some work has also been done with selective precipitants, such as sodium polythiocarbonates (Bucknam, 2007), and 1,3-benzenediamidoethanethiol (Matlock, 2002). Common problems with these approaches include introduction of a solid:liquid separation step, reagent costs, the need to measure the mercury concentration for process control for minimizing silver losses, and regulatory requirements to retort otherwise stable mercury concentrates."

Jan 1, 2015

By M. A. Rabah

This paper focuses on the separation and extraction of lead and zinc from Egyptian ore at the Eastern Desert close to Red Sea. The ore sample contains cerussite, galena, hemimorphite and other impurities. Experimental program includes flotationof galena using xanthate collector and cerussite using oleic acid as collector and sodium silicate to depress hemimorphite tailing. Galena, and hemi-morphite are converted to carbonate with sodium carbonate prior to metal extraction. Lead and zinc are extracted pyrometallurgically at 1050°C and750°C or electrochemically respectively. The overall performance of the applied method amounts to 99.2%. Extraction efficiency of lead and zinc amounts to 98% and 94.5 % respectively. A model assumed that galena and cerussite in the ore are partially oxidized and can be liberated by grinding. Oleic acid selectively reacts with cerussite in a multistep sequence. Preliminary cost estimate shows that the price of the products is competitive to their local market prices.

Jan 1, 2000

By Laura McNally

In 2006, McNally International Inc., in a joint venture partner-ship with Aecon Constructors, was the successful bidder on two York Region Tunnel Projects: the Bathurst Collector/Langstaff Trunk Sewers and the York Durham Sewer System (YDSS) Interceptor Sewer 19th Avenue, both in the Toronto area. These projects comprised a total of 13 km (8 miles) of 2.74 m (9 ft) finished diameter tunnels and are both part of the YDSS. Both contracts required the use of earth pressure balance (EPB) tunnel boring machines (TBM) with a precast concrete segmental liner.

Jan 1, 2008

By C. A. Young, J. D. Miller

Thermodynamic data has been obtained for oleate chemisorption at fluorite (CaF2) and calcite (CaCO3) surfaces using adsorption isotherms determined previously at room and elevated temperatures by in-situ Fourier transform infrared/internal reflection spectroscopy (FT-IR/IRS). Linear regression analysis was used to statistically derive free energy data as a function of temperature assuming oleate chemisorption followed Langmuir-type adsorption. Enthalpy and entropy changes were subsequently ascertained from the Clausius-Clapeyron equation and fundamental thermodynamic relationships. Essentially, no difference in the free energy of chemisorption at the two mineral surfaces was found; however, the differences in enthalpy and entropy values were significant. By comparison, the results showed that oleate chemisorption at fluorite surfaces was more extensive and more entropically driven due to more water being displaced. Results correlate well with values determined in the literature for other mineral collector systems. These findings help explain the greater hydrophobic character of fluorite than calcite in both the absence and presence of oleate.

Jan 1, 2002

By C. S. Kucukkaragoz

An ilmenite concentrate was reduced in the solid state with carbon under argon atmosphere at temperatures between 1000oC and 1400oC. The ilmenite concentrate and 50% excess carbon were reacted to achieve the highest attainable degree of reduction at each temperature and the reaction products were subjected to a series of analytical work by optical microscopy, X-ray diffraction analysis and SEM ( EDS) analysis. The ilmenite remained unaltered at 1000oC and had a slight change in its composition at 1050oC. A secondary oxide phase containing metallic nuclei was detectable at 12% reduction at 1100oC. The reduction of TixOy took place in a sequence changing the y/x ratio from 2.0 to a value less than 1.0 at 84% reduction at 1400oC. Metallic phase consisted of Fe and C initially and started to include Ti at the later stages. Complete reduction of TixOy to metallic Ti was not possible at these temperatures.

Jan 1, 2005

By G. Swartz, R. J. Brison, R. A. Wyman, J. P. Vandenhoeck, S. E. Khalafalla

Magnetic fluids are commonly composed of ultrafine submicron particles of magnetite (Fe3O4) dispersed in either a kerosene or a water carrier medium with oleic acid as a protective colloid. The unique property of these fluids is that when the magnetic particles are attracted to a magnet the carrier medium moves along with the particles so that the liquid also appears magnetic. The availability of a fluid whose gross behavior changes sharply in a magnetic field without affecting its rheologic characteristics is becoming critical for many technologic applications. About two gener¬ations ago suspensions of relatively large, micron-sized ferromagnetic particles in oil proved useful in clutches, brakes, and dashpots. These were called magnetic clutch materials, and their viscosities were highly dependent upon the applied magnetic field, in contrast to true mag¬netic fluids which retain their fluidic characteristics under all applied fields and field gradients. While the term "ferrofluid" was used by Rosensweig and Kaiser&apos; to designate a magnetic colloid composed of a dispersed magnetic ferrous material, the more general term, "mag¬netic fluid," is preferred. This is because these fluids may contain ferro- or ferrimagnetic substances, such as cobalt, nickel, gadolinium, dysprosium, or magnetic ferrites in carrier liquids, such as hydrocar¬bons (kerosene), silicones, water, fluorocarbons, etc. Preparation of Magnetic Fluids Magnetic fluids were first prepared by Papell and Faber, at the NASA Lewis Research Center, Cleveland, Ohio, by tumbling ferrite materials for several weeks in a carrier medium (such as kerosene) and a dispersing agent (such as oleic acid) with steel balls. Rosensweig et al.1 compared the stability of their ferrofluids obtained from both metallic iron and the magnetic oxides of iron, Fe3O4 and yFe2O3. They found that, although the saturation magnetization of iron is 3.5 times greater than that of magnetite, its colloidal solutions deterio¬rated much more rapidly. The iron particles were undoubtedly rapidly oxidized to a nonmagnetic state due to the enormous surface area of these colloidal particles. Because the properties of these fluids are highly dependent on particle size and may acquire opposite characteristics by small incre¬ments in that size, more controllable methods of preparation have been developed recently by Khalafalla and Reimers.6 In one method metastabilized pyrophoric wiistite is ground to colloidal size in a kerosene oleic acid mixture, and then it is disproportionated to colloi¬dal magnetite and iron at temperatures just below the eutectoidal temperature of wüstite stability (570°C); thus, t < 570°C 4 FeO t > 570°C Fe + Fe30, (1) Because of its antiferromagnetic characteristics, the precursor wüstite is much easier to grind than magnetite. Another method3 avoids grinding entirely and utilizes a peptiza¬tion technique from ferrous materials in the molecular state of aggrega¬tion. This latter procedure has resulted in preparation of strong fluids at considerable savings in cost.

Jan 1, 1985

Over the past seven years a large database of coal self-heating rates under adiabatic conditions has been developed at The University of Queensland. Coals have been tested from Australia (Queensland and New South Wales), New Zealand (North and South Island), Indonesia and more recently the United States. As a result of this work, definitive relationships and trends have been established for the effects of various intrinsic coal properties on self-heating rates and anomalous coals have also been identified. Previously held views on the effects of coal rank, type and inorganic constituents are examined in this paper. Many of the published relationships do not hold true in terms of coal self-heating rates. A propensity rating scheme has also been developed which is routinely used in Australia for assessing coals and identifying appropriate mining analogues for spontaneous combustion management planning. A selection of examples will be presented in the paper, which shows the significance of this assessment strategy.

Jan 1, 2009

By W. K. Hitchcock

Anecdotal evidence suggests that re-entering a sealed heating poses a significant hazard, whereby the original heating is rejuvenated at an accelerated rate forcing withdrawal and re-sealing of the area. Bulk-scale laboratory experiments using a two-metre column confirm these mine site observations. A high volatile bituminous coal from New South Wales, Australia was allowed to develop a significant hot spot before being inerted with nitrogen and allowed to cool. Air was then allowed back into the coal after the nitrogen was turned off and a hot spot developed almost immediately at the same location as the original hot spot before it quickly migrated towards the air source within a day. Two more re-entries were simulated. Each successive re-entry developed a broader hot spot and took longer to reach thermal runaway. These results clearly show the behaviour that can be expected when trying to recover a section of an underground coal mine that has been sealed due to a spontaneous combustion event.

Jan 1, 2009

Most statistical and geostatistical methods of re-source and reserve estimation work extremely well for Normal (Gaussian) well-behaved information. However, most interesting mineral deposits exhibit far from this idealistic distribution of values. It seems that the more valuable the mineral, the less likely the data are to have a Normal distribution. Values tend to be "positively skewed" with a long tail into the high values. Using averaging techniques, such as inverse distance or ordinary kriging may result in consider-able overestimation of grades and tonnages unless such values are cut or otherwise modified. This paper presents some real case studies where distributions are (a) highly skewed and (b) the product of multiple phases of mineralisation. Practical methods are presented for solving such problems including combinations of indicator and log normal kriging methods. The emphasis of the presentation is on developing operational methods which can be used on project evaluation or grade control in producing mines.

Jan 1, 2000

By F. F. Roberto

Many techniques that are used to characterize and monitor microbial populations associated with sulfide mineral bioleaching require the cultivation of the organisms on solid or liquid media. Chemolithotrophic species, such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, or thermophilic chemolithotrophs, such as Acidianus brierleyi and Sulfolobus solfataricus can grow quite slowly, requiring weeks to complete efforts to identify and quantify these microbes associated with bioleach samples. Real-time PCR (polymerase chain reaction) assays in which DNA targets are amplified in the presence of fluorescent oligonucleotide primers, allowing the monitoring and quantification of the amplification reactions as they progress, provide a means of rapidly detecting the presence of microbial species of interest, and their relative abundance in a sample. This presentation will describe the design and use of such assays to monitor acidophilic microbes in the environment and in bioleaching operations. These assays provide results within 2-3 hours, and can detect less than 100 individual microbial cells.

Jan 1, 2009

By J. P. Ferro, W. H. Stewart

Wet ground and dry muscovite mica continued to be the most commercially significant types of mica in the US. Canada&apos;s phlogopite mica and some US deposits of sericite mica have also contributed to the overall application of mica in a variety of industries. Mica&apos;s major end uses are paint, rubber, and construction material. Its value was about $30 million last year. The southern Appalachian Mountains weathered granitic bodies and pegmatites continued to be the primary US muscovite mica source. North Carolina production of mica as a coproduct of feldspar, kaolin, and lithium processing accounted for more than 60% of the total output. New Mexico, South Carolina, South Dakota, Georgia, and Connecticut accounted for the rest. Flake mica was also produced from mica schists in North Carolina and South Dakota. It is also being investigated in Ontario, Canada. Wet ground mica Wet ground mica was produced by four companies: KMG Minerals, Franklin Mineral Products, J.M. Huber Corp., and Concord Mica. KMG and Franklin Mineral Products accounted for more than 80% of the production. Wet ground mica is a highly delaminated platey powder used to reinforce solvent and aqueous system paints for increased weatherability, durability, and greater resistance to moisture and corrosive atmospheres. In plastics, it is an excellent filler and reinforcing agent, providing better dielectric properties, heat resistance, and added tensile and flexural strength. In the rubber industry, wet ground mica is used as a mold lubricant to manufacture molded rubber products, such as tires. It also acts as an inert filler that reduces gas permeability. Miscellaneous uses include additives to caulking compounds, foundry applications, lubricants, greases, silicone release agents, and dry powder fire extinguishers. Wet ground mica prices range from $353 to $496/t ($320 to $450 per st) fob plant. Specialty products may be higher, depending on customer requirements. Dry ground muscovite mica Dry ground mica was produced by nine companies: KMG Minerals, Unimin, US Gypsum, Mineral Industrial Commodities of America, Spartan Minerals Corp., Asheville Mica Corp., Deneen Mica Co., Pacer Corp., and J.M. Huber Corp. Dry ground mica&apos;s primary market is wallboard joint compound. Here, it is a functional extender that improves the physical properties and finishing characteristics of the mud. It is also used in various grades as a filler in asphalt products, enamels, mastics, cements, plastics, adhesives, texture paints, and plaster. Dry ground mica became popular as an additive in oil well drilling fluids, where the mica flakes platey nature helps seal the well bore, preventing circulating fluid loss. But oil&apos;s dramatic price drop and consequent curtailing of well drilling brought this once booming market to a virtual halt. Forecasters predict that this business will gradually pick up during the next few years and most current dry ground mica producers will again produce the oil well drilling material. Dry ground mica prices range from $110 to $420/t ($100 to $380 per st) fob plant. High quality sericite mica, sometimes referred to as an altered muscovite, was mainly produced by two US companies. Mineral Industrial Commodities of America and Mineral Mining Corp. have equivalent capacities of about 27 kt/a (30,000 stpy). The majority of the material produced was consumed by the joint compound industry. Minor uses are in paint and oil well drilling. The lack of ground sericite penetration into the traditional ground muscovite markets is attributed to high silica content, typically in excess of 20%, and a bulk density. Prices range from $88 to $187/t ($80 to $170 per st) fob plant. Phlogopite mica is a dark colored, magnesium bearing mica rarely found in the US. Suzorite Mica Corp., a division of Lacana Petroleum, mines a deposit in Quebec that is 80% to 90% phlogopite. The dark color has prevented the material&apos;s entry into the traditional paint markets. But the physical properties and high purity make it useful as a low-cost reinforcing filler in many plastics and several asphalt applications. Phlogopite mica is ground to several grades and may be treated with various surface coatings for use in plastics or coated with nickel for EMI/RFI shielding applications. Prices for phlogopite products range from $144 to $580/t ($104 to $580 per st) fob plant. As in recent years, production of domestic muscovite sheet - block, film, and splittings - remained insignificant. These resources are limited and uneconomic due to the high cost of hand labor required to process sheet mica in the US. Imports from India and Brazil were the primary sources of the estimated 1 kt (2.4 million lbs) valued at $2.5 million consumed by US electronic and electrical equipment manufacturers in 1986. Reserves As a feldspar, kaolin, and lithium industry coproduct, flake mica will continue to provide a large percentage of mica re- This summary of 1986 mica activity was received too late to be used in the June issue.

Jan 7, 1987

By Nelson R. Shaffer

Biotechnology has become a household word of the nineties, and it is expected to become as important in the next century as the computer is in the present. Numerous books and articles portray biotechnology developments as nothing less than a scientific revolution. Almost everywhere one looks new biotechnical breakthroughs are being reported that offer almost limitless opportunities to harness the force of living things to produce materials and manipulate their properties. Biotechnology has been broadly defined as any applications of biological organisms, systems, or processes to manufacturing and service industries. This seemingly new technology is, in fact, one of mankind&apos;s oldest scientific activities (Table l), which has been recently revolutionized by techniques of genetic engineering that arose out of basic research in biology, biochemistry, genetics, and information sciences. From fields as old as agriculture and medicine to those as new as monoclonal anti-bodies, transgenic plants, or biocomputers are encompassed by biotechnology. Like most human endeavors, industrial minerals play critical roles in biotechnology. In addition biotechnology holds real potential to improve extraction and beneficiation of certain industrial minerals themselves. BIOTECHNOLOGY OVERVIEW Companies using established biotechnical techniques make up large and diverse groups such as agriculture, chemicals, and pharmaceuticals. The massive US Pharmacopia (Anon., 1990a) provides detailed specifications for minerals used in medicines. Alumina, zirconia, apatite, and bioactive glass have seen service as implant materials (Williams, 1990) and new uses for minerals in health sciences are being actively researched. Agriculture produced $361 billion worth of food and drink during 1991 in the United States; organic chemicals, pharmaceuticals, and enzymes accounted for $68, $59, and $42 billion, respectively (Anon., 1992a). It is not possible to separate the contributions of industrial minerals to biotechnical products, but they represent a very large and rapidly growing new field of uses. The new biotechnology has nearly 300 small companies, plus 15 established companies with 742 biotechnology-related firms (Dibner, 1991b). Revenues exceeded $2 billion in 1990 and are expected to grow to $50 billion by 2000 (Anon., 1992c), with worldwide sales exceeding $100 billion (Burrill and Roberts, 1992). Federal research amounted to $3.4 billion in 1990 (Anon., 1992b). The United States is the world leader in biotechnology, but other countries have large, well-funded programs. Despite debate about safety, obstacles to new biotechnology products are declining (Embers, 1992, Gibbons, 1991). Fifteen biotechnology drugs valued at $1.2 billion (Thayer, 1991a) are on the market, and more than 100 are in various stages of testing (Edington, 1992). Many diagnostic tests are also in use or development (Demain, 1983, Anon., 1992). Large scale efforts to produce or transform important chemicals are also underway (Ng et al., 1983, Hinman, 1991), and research into geologic uses of biotechnology has begun. Much has been published about microbial mining, oil recovery, desulfurization, bioremediation, and other geologic aspects of biotechnology, but this chapter is the first attempt to explore interactions of biotechnology and industrial minerals. This chapter examines uses of minerals in biotechnology; how biotechnology can be used to discover, recover, and beneficiate industrial minerals; and speculates on some potential, but as yet untried uses. Definitions What exactly does the word biotechnology mean? Bud (1989) states that the first use of the term was by Karl Ereky in 1919 to cover the interaction of biology and technology, and in 1933 the term was used in Nature. After citing seven different definitions, Smith (1988) concludes that biotechnology is a series of enabling technologies involving practical applications of organisms or their subcellular components to manufacturing and service industries or to environmental management. Walker and Cox (1988) suggest a definition of "the practical applications of biological systems to the manufacturing and service industries and to the management of the environment." Primrose (1991) says that it is "the commercial exploitation of living organisms or their components." There is essentially an older broad use of the term and a new use. The US Office of Technology Assessment (Anon., 1984) uses a broad definition that includes any technique that uses living organisms (or parts of organisms) to make or modify products, to improve plants or animals, or to develop micro-organisms for specific uses. Definitions are different, but they all have several fundamental elements that include the control, management, or manipulation of living things for commercial, industrial, or useful ends. While such a definition encompasses all of agriculture in practice the "new" biotechnology is restricted to processes involving microorganisms-plant and animal cells, or enzymes. Many consider biotechnology to be recent, but it is one of our oldest technologies as evidenced by the prehistoric origin of brewing, cheese-making, and other techniques. [Table 1] gives some of the important developments in the history of biotechnology. Smith (1988) breaks down historical developments of biotechnology into four phases: 1) prehistoric with no understanding of underlying processes; 2) nonsterile processes; 3) sterile processes after 1940; and 4) genetic and recombinant DNA technology deliberate design of special organisms or processes.

Jan 1, 1994

By Gordon T. Austin

Garnet is the general name for a family of complex silicate minerals having similar physical properties and crystallizing in the isometric (cubic) system. All garnets have the same general chemical formula but vary greatly in chemical composition. The name garnet is derived from the Latin word granatus, meaning like a grain, which refers to the mode of occurrence wherein crystals resemble grains or seeds embedded in the matrix. GEOLOGY Mineralogy Chemical Properties: The general formula for garnet is A3B2(SiO4)3, whereas A can be calcium, magnesium, ferrous iron, or manganese, and B can be aluminum. ferric iron, or chromium, or rarely titanium. The formulas and names of common garnet species are: [ ] Almandite and almandite-pyrope solid solution garnets are the best abrasive types, but andradite, grossularite, and pyrope also are used. All species of garnet have been used as gemstones. The structure of garnet consists essentially of isolated SiO, tetrahedra connected by oxygen-cation-oxygen bonds through the distinct A and B group cation sites. Within this structure magnesium, ferrous iron, and manganese easily interchange and substitute for each other in the A cation position, and calcium does so less readily. Additionally, aluminum, femc iron, and chromium substitute for each other to a limited extent in the B cation position. This ability to substitute or exchange ions without changing the crystal structure is called isomorphism, and garnet is one of the finest examples of a isomorphous series. Because of this isomorphism there is complete solid solution between certain garnet species but not between others. Fig. 1 illustrates these solid solution relationships. Some rare species of garnet are known that illustrate the wide range of cation substitution that the garnet crystal structure can accommodate. They include: [ ] These rare species are not of interest for industrial applications, but can be of interest to mineralogists and the gem industry. Physical Properties: Garnet displays the greatest variety of color of any industrial mineral. Garnets have been found in all colors except blue. For example, grossularite can be colorless, white, gray, yellow, yellowish green, various shades of green, brown, pink, reddish, or black. Andradite garnet can be yellow- green, green, greenish brown, orangy yellow, brown, grayish black or black. Pyrope is commonly purplish red, pinkish red, orangy red, crimson, or dark red; and almandite is deep red, brownish red, brownish black or violet-red. Spessartite garnet can be red, reddish orange, orange, yellow-brown, reddish brown, or blackish brown. A few garnets exhibit a color-change phenomenon. They are one color when viewed in natural light and another color when viewed in incandescent light. Because of the great variation in color of garnet within each species and similarities in color between garnets of different species it is recommended that garnet identification not be based on color alone. The Mohs hardness of garnet varies from 6.5 to 9.0. Grossularite and uvarovite have a hardness of 6.5 to 7.5; andradite is 6.5 to 7.0; and pyrope, almandite, and spessartite are 7.0 to 7.5 in hardness. There are reports of almandite having a hardness of between 8.0 and 9.0. As with hardness, the specific gravity of garnet varies considerably. The specific gravity may be as low as 3.2 or as high as 4.3 depending on chemical composition. Garnet crystallizes in the isometric system with rhombic dodecahedra and trapezohedra the most common forms. Crystals also form in combinations of dodecahedra and trapezohedra or either of these in combination with hexoctahedra. Crystals can have cubic or octahedral faces, but these are rare. Under favorable conditions of formation garnet will crystalize in nearly perfect forms that rival study models. Garnet also forms as irregular blebs, grains, knots, or masses, with or without distinguishable crystal faces, and as coarse- or fine-grained granular masses that appear to be totally lacking in crystal form. The fracture of garnet also shows great variation. In some garnets, particularly those that are well crystallized and glassy in appearance, the fracture is subconchoidal to conchoidal. Other, more poorly crystallized garnets exhibit a fracture that can only be described as uneven. Garnet occasionally has an indistinct dodecahedral cleavage. Certain species of garnet from specific locations have a pronounced laminated structure consisting of planes of weakness along which parting takes place. This parting may resemble cleavage, but since it is mechanical and not related to crystal structure it is not true cleavage. The optical properties of garnet are sensitive to even small changes in chemical composition or strain in the crystal structure. For this reason each species does not have a single index of re- fraction (IR) but has a range of 1Rs. Uvarovite in its pure form should have an IR of 1.870, but in nature samples vary from 1.74

Jan 1, 1994

By R. Fedors, T. Ghezzehei, D. Or

The phenomena of dripping into cavities (e.g. tunnels and drifts) within an unsaturated fractured porous medium under ventilated conditions is studied to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect the integrity of high-level nuclear waste packages placed in drifts. The sensitivity of dripping rates and water chemistry to ventilation is analyzed at various flow rates using analytical expressions linking flow on fracture surfaces to drop formation and evaporation. The model was tested using laboratory experiments involving machined aluminum slabs designed to represent a simplified morphology of a fracture face intersecting a cavity and using natural fracture surfaces from a welded tuff. Comparison with ten years of data on dripping in natural caves showed good agreement with model predictions. In particular, for low dripping rates, evaporation due to ventilation leads to larger drop sizes and alters drop chemistry by increasing the concentration of solutes in the drop relative to that in the water flowing on the fracture face.

Jan 1, 2000

By Yuemin Zhao, Daniel Tao, Xinxi Zhang, Qingru Chen, Maoming Fan, Zhenfu Luo, Xiuxiang Tao, Guohua Yang

Coal is currently cleaned with the minimum of size reduction, fine particle processing, recovery, and tailings disposal are major problems. Adequate water resources are not always available. For example, two thirds of China&apos;s coal is located in arid areas. Hence, dry separation provides an alternative approach. Of the dry coal separation methods available, air dense-medium fluidized beds have been used to separate 50~6mm coal efficiently. However, excessive bubbling and back mixing of the separated solids in the air-dense media fluidized bed causes the high lower size limit of 6mm for the feed material, this affecting the preparation efficiency. Based on prior study on air-fluidized dense media for 6~50mm coal preparation, this paper presents methods and test results on the fine coal dry classification, static electricity beneficiation of 0~0.5mm coal, and magnetically stabilized fluidized beds for separating 0.5~6mm coal.

Jan 1, 2005

By J. Trow

Dowsing is really IESG which inductively locates electric gradients (dv/dx) on the flanks of SP anomalies. "Sensors" are in one?s head. The "meter" consists of one?s body, limbs, and two $.69 welding rods. The method was calibrated near Mamainse Point, Ontario, where IESG-negative chalcopyrite-bornite-chalcocite-native copper ores reveal mineral zoning related to the IESG-positive Keweenaw fault, down which oxidizing solutions moved. In Michigan, the IESG-positive Keweenaw fault suggests that oxygen-bearing solutions from the Jacobsville Sandstone moved downward to oxidize hydrothermal sulfur to produce native copper, and to supply sufficient water to satisfy Walter White.

Jan 1, 1992

By Irwan Halim, Seung Han Kim

This paper will describe design of precast segmental tunnel lining for the Pawtucket CSO Tunnel Project in Providence, Rhode Island. The tunnel is 11,700 LF long with 30-foot finished diameter to be constructed in complex sedimentary rocks. Special features of the segments include a large keystone and no connector used on radial joints. The typical segments will be steel fiber reinforced, and hybrid segments with additional steel rebars and shear bicones will be used around the adit openings without use of any structural framing. The important design considerations will be discussed, including special 3D segment to adit connection analyses performed.

Dec 1, 2022

By Basilio Giurgola, Jeremiah M. Jezerski, Filippo Azzara, Federico Bonaiuti, Russell H. Lutch

The Northeast Boundary Tunnel Project consists of a 23 ft diameter, 27,000 ft long, CSO tunnel, multiple underground connections, and significant surface works within an urban corridor. The NEBT alignment depths range from 60 to 140 ft and includes seven shafts ranging in depth from 77 to 155 ft with diameters varying from about 19.5 to 56 ft, some as in-line connections and others required adits for connection to the main tunnel. This paper focuses on the design and construction of two major underground connections which are the First Street Connector Tunnel and the Mount Olivet Road Diversion Sewer.

Jun 13, 2023

By Gamal Rashed, Tim Miller, Nicole Evanek

High horizontal stress has been identified as a critical factor affecting roof stability in underground mines, particularly when the immediate roof consists of weak or laminated rock. Numerical models were employed to better understand the influence of caprock thickness, cutting sequences, and the orientation of driving direction relative to maximum horizontal stress on roof stability in underground stone mines. These models were calibrated based on field observations of roof falls from the study mine. The findings of this study enhance our understanding of roof stability under high horizontal stress and contribute to reducing the risk of roof falls in underground stone mines.

Feb 1, 2025