Search Documents

By D. W. McGlashan

[Comideha;tion o 4 chyakd- chem and aLtuctund phopetttiu o auRdide nm&, The in~o/uncction gained h ;to be uned ;to iM;tmph& ( I! dnukey bho hen mind-aundacu , ( 2 ) modidicakio~n 06 ;the minmd n~tdacu, and (3) eac;tiom at ;the mind adac fnom ;thu e baic din oipfina, concep;tc, wLth hegattd ;to .the changen kha;t awtgacu undehgu, heac;tiom kha;t might take place, ,the geom&y 04 ;the inkmduce, ;the nkde 04 diddmenk &om and iom in ;the intmdace, and okhm phyaicd and chemicd pttopemXu od an intmdace mun;t be developed, weighed and appfied. The au/tho~ ded wah thue concep;tud connidmatiom @om which hypokhuu me n& ko denchibe khe envhomenkd-ivttadaciae hela;tiomhipa doh nevmd nddide minettah, The ch&enge and moltivation in khe hu eattch h in a henhe a deattch doh baic dad and helcctiomkipa needed doh accompfi he&.] INTRODUCTION Qualitative and quantitative explanation of particulate solid separations are unknown entities because of the lack of adequate models and mathematical relationships to explain the activity occur- ring between the solid and liquid phases. It is a transitional region in which it is difficult to ascertain the mechanisms of adsorption of ions, molecules, etc. on mineral surfaces, as well as other secondary reactions which occur in interfacial regions. Thus, in this paper the authors deal with conceptual considerations from which hypotheses are set forth to describe the environmental- interfacial relationships for sulfide minerals.

Jan 1, 1968

By Tom Dettweiler, Robina Sharpe, Wright. Michael

The International Seabed Authority and a number of countries have or are in the process of developing environmental impact assessment guidelines and legislation for seafloor mineral development. The formal decision to grant a project an environmental permit is based on an environmental and social impact assessment (ESIA), culminating in an environmental impact statement (EIS). The EIS needs to be supported by sufficient data upon which an assessment of impacts can be made and mitigation measures developed. Given the remote locations of many seafloor prospects, collection of sufficient environmental data to inform an EIS is often a difficult, expensive and lengthy process.

Sep 1, 2014

By Robert Vergie

Like most of you, I would rather work on a job than talk about it. But it is fruitful to spend some time taking stock of important developments in the heavy construction field. One of the strongest recent movements affecting the industry has been the push for safety. I regret that it is a recent development. Not that builders were against safety. Too often though, it was easier to continue with dangerous old work methods than to try something new. Too often, it was easier for equipment manufacturers to build production tools with little consideration for worker safety. And too often, accidents and gruesome disasters occurred. The ultimate result of on-the-job injuries in construction and other industries was the Federal Government's Occupational Safety and Health Act of 1970. Individual states were required either to accept OSHA or pass updated regulations at least as stringent as the Federal requirements. These new rules must be strictly obeyed -- not just because they carry civil and criminal sanctions -- but because they correct unsafe conditions and reduce hazardous acts. Though some OSHA measures have been criticized as superfluous, most of them do in fact save lives and limbs. Equally important, the tunneler who follows the new safety regulations can be fairly certain of an efficient, uninterrupted operation. Regulations do sometimes bring rewards.

Jan 1, 1974

By G. Lawrence, R. Pieters, A. Leung, T. Pedersen

The Main Zone and Waterline pit lakes at the Equity Silver Mine near Houston, BC (Canada) are the sites of a new 3-yr research program with three primary goals: 1) understanding controls on metal concentrations in the lakes; 2) using mesocosms to test a variety of remediation strategies; and 3) verifying and improving an existing coupled physical-geochemical model with the goal of improving predictions of pit lake water quality. Initial data from two summer surveys in the Main Zone pit lake reveal elevated dissolved metal concentrations (e.g. [Zn] as high as 800 µg/L) present in a two-meter-deep mixed layer, and elevated particulate metal concentrations towards the bottom of the water column. Hydroxide sludge, a byproduct of ARD treatment, is being discharged to the surface waters of the Main Zone pit lake. The sludge sinks rapidly to the lake bottom, leading to deep waters with elevated levels of dissolved O2 and total metals. By contrast, the deep waters of the proximal Waterline pit lake are mildly reducing, manifested by depletion of O2 and elevated levels of dissolved Fe. These reducing conditions have led to elevated levels of As (up to 1500 µg/L) in Waterline pit deep waters. The contrasting behavior of these two pit lakes, as well as the processes controlling metal concentrations in the lakes, will be discussed.

Jan 1, 2002

By W. L. Garrison

Improvements continue to be made in rapid excavation and tunneling technology. There are several ways to examine the impacts of such improvements. The most common procedure is to monitor current developments and to evaluate prospects for expansion of present types of uses. Other approaches are called for, however, if the technology might be used in ways not now imagined, if the search is for information for managers of technology development, and if the issue is that of the wise use of the technology by society. The first section of the paper will pose these matters as questions. These questions will be examined from the point of view of the processes of technology development and utilization, and then further examined against the backdrop of processes at work within the urban area. Such an examination will provide insight into the way technology developments should proceed. The final section will present some comments that may be useful to those guiding the development of the technology and to those who might provide leadership for its wise utilization. THE QUESTIONS Three questions are posed: 1. Are there uses for the technology beyond further penetrations of its present markets? 2. Can information be supplied to managers of technology development so that they may improve the assignment of priorities among development choices? 3. How can society make wiser use of the technology?

Jan 1, 1974

By M. W. Springett

During the 1970's geostatisticians were often accused of not paying sufficient attention to geologic features in the computerised generation of ore reserves. Unfortunately this charge was all -too-often justified and the results of such studies tended to be oversimplified and failed to reveal the full potential of computerised reserve estimation and geostatistical methods. There were some notable exceptions to this trend. Techniques were described that paid a great deal of respect to the geologic characteristics peculiar to certain deposits (Rendu J-M, 1984, Barnes T. E., 1982). At Gold Fields several techniques have been developed for handling the geologic characteristics of ore bodies for reserve estimation purposes. These have developed over time and the evolution of their adoption has been a reflection of our own learning experience from the practical application of computerised reserve estimation on many precious metal s deposits. Problems Typical problems that have been experienced by ourselves and which we have learned to guard against and watch for are: ? "smearing" at geologic contacts ? confusion caused by disparate "selective mining unit sizes" and block sizes ? conflicting estimates generated by field staff using various versions of the polygonal method ? problems in generating meaningful variograms

Jan 1, 1985

By W. Haupt, M. Thormé, H. J. Ertle, K. Reim

Though Germany has a very old mining history, her experience in uranium mining only started in the late sixties. Today in the Federal Republic of Germany (FRG) there are only 5 small mines in the exploration stage, namely Menzenschwand and Müllenbach in the Black Forest and Mähring, Popenreuth and GroBschloppen in northern Bavaria. In all these exploration mines much development is required to define shape and size of ore bodies. Mining engineers, government authorities and environmentalists alike are very much concerned about environmental safeguards and protection of mine workers against radon and its daughter products. Miners are affected by internal and external radioactive exposure. In general the external [f3]- and [µ] -exposures can be considered as small in comparison to the internal exposure and are therefore not discussed in this paper. The internal exposure is caused by the inhalation of radon and its daughter products and is relevant to the lung as the critical organ. The nobelgas radon is inert and does not from compounds with other elements easily. Contrary to the physical half-life of 3,8 days the biological half-life of radon is only 10 to 20 minutes. During the rentention time in the body only approximately 1 % of the long-lived decay products are retained in the system (SCHOGER, 1976). In this connection is it important that the radon resorption as well as the radon secretion varies individually and depends to a large extent on the age of the person (SCHOGER, 1960). RENOUX et al. (1978) have determined that the greatest part of the a(-activity in the air is attached to aerosoles with a diameter of 0,4/14. The radiation exposure of the lung by radon is negligible if compared with the exposure by short-lived decay products. For this reason one has introduced the concept of the potential [o](-energy (P) of the short-lived radon decay products, which means the total [ct]-energy, which is produced when an atom decays in the decay-series down to the long-lived lead-210. [ ] The unity of the potential [o]-energy concentration in the SI-system is 1 j/m3 air. In radiation protection however a specific unit is used namely the working level (WL): [ ] The WL-unit, though internationally recognised has not been introduced officially in Germany. Because of the large amount of tunneling still to be done in the FRG, the various mines departments responsible for safety and health in mining ask searching questions such as: - What are the laws governing radon emanation in tunneling? - Can workers be adeguately protected against radiation hazards? - How should one drive through high grade uranium ore? - What happens if the ventilation system breaks down?

Jan 1, 1981

By Abdelaziz Baçaoui, Imane Aarab, Mohammed Derqaoui, Abdelrani Yaacoubi, Khalid El Amari, Abdelmoughit Abidi, Abderahman Etahiri

Numerous researchers have addressed the complexity of the direct flotation separation of apatite from low-grade phosphate ore. The majority of these studies were limited to the micro-flotation scale. In fact, there is no warranty that a reagent scheme that showed a direct flotation of apatite at a micro-flotation scale on pure minerals would automatically replicate the same expected results on the natural ore in the mechanical flotation cell and so was the case for the phosphate ore studied. The overall trend was concentrating apatite in the non-float product. This study aspired to thoroughly assess the flotation performance of this never-exploited low-grade sedimentary phosphate using design of experiments (DOE). Unveiling new insights on such a strategy twist, various parameters and operating conditions, namely, desliming, type of collector and depressant, reagents dosages, conditioning times, flotation time, and pH, were addressed by multiple-factor screening using asymmetrical fractional factorial design followed by statistical interpretations. The collectors tested were the sodium oleate and a fatty acid mixture (FAM). The depressants tested were sodium alginate (NaAL), corn starch, carboxymethylcellulose (CMC), and sodium silicate. The results of the multivariable analysis revealed that desliming, pH, collector dosage, and flotation time significantly influenced the flotation process. Desliming was beneficial for the yield, P2O5 recovery, and SiO2 removal; however, there was still a compromise between grade and recovery. A strongly alkaline pH value of 12 stood out from the whole range. P2O5, CO2, and SiO2 grades of the products and flotation recoveries were improved, except for P2O5 recovery, which was negatively affected. A collector dosage between 2000 and 3000 g/t increased the P2O5 grade and reduced CO2 grade and recovery, enhancing the apatite/carbonates separation. A flotation time of 15 min was significant for P2O5 grade and CO2 recovery, nevertheless, at the expense of yield and P2O5 recovery. The products having initial concentrates of 28.08% P2O5 with a recovery of 88.96% and 29.41% P2O5 with a recovery of 62.71% were obtained using 25 g/t of NaAL and 2000 g/t of the collector FAM and sodium oleate, respectively, at pH 12.

Jun 5, 2022

By G. Myers, C. J. Wendt, W. H. Wilkinson, M. D. Dennis

Precious metal mineralization at Mt. Hamilton, NV is associated with a polymetallic, garnet-pyroxene skarn system developed in middle to upper Cambrian calcareous shale, limestone, and dolomite. The skarn is developed around the Cretaceous Seligman and Monte Cristo calc-alkaline stocks. Gold is associated with intense retrograde alteration. Later epithermal quartz veins contain gold, silver, base-metal sulfides, and sulfosalts cross-cut skarn alteration. Westmont Mining Inc. is currently developing two mineralized zones containing a geologic resource of about 7 Mt (7.7 million st) that averages 1.7 g/t (0.05 oz per st) gold and 17.2 g/t (0.5 oz per st) silver. The project will have an estimated mine life of seven years, with a planned annual production rate of I t (35,000 oz) of gold and 9.3 t (300,000 oz) of silver.

Jan 1, 1990

By H. Akbari

The ordinary Portland cement (OPC) is the key pozzalonic component of the concrete mix, widely used as the construction material world-wide. Billions of tons of OPC are used in the construction industry each year. However, calcinations of limestone and silica that produce OPC also produce almost an equal amount of CO2 during the cement manufacturing process. Thus, OPC production accounts for nearly 7% of all anthropogenic CO2 emission each year. The main objective of this study was to develop a geopolymer-based composite to be used as a substitute for OPC in concrete application to significantly lower the carbon foot print of the construction industry. A waste material produced during the coal combustion process was used as the main raw material for the geopolymer-based composite. It was mostly the non-metallic content of the F-type fly ash produced from the combustion of bituminous coal. The authors envisioned to extract some of the valuable metal oxides from fly ash prior to using the major non-metallic portion of the fly ash for geopolymer concrete application. The results obtained from this study exhibited that the compressive strength of the geopolymer concrete compares favorably with that of the conventional concrete prepared using the OPC.

Feb 27, 2013

By Rodrigo Jerez

Advances in inexpensive computer automation led to the development and use of a computerized ore control system at the Cyprus Copperstone Gold Mine near Parker, AZ. These new ore control practices improved accuracy, performance and productivity of the ore control effort. An automated system for data collection, including bar coding of blasthole samples, laboratory analysis, data management, grade estimation, cut delineation and ore zone stake out, plays a major role in ore control practices. This is of particular interest because of the large amount of blasthole information being processed, analyzed and reported daily. Copperstone Gold management has been progressive toward new, efficient methods regarding ore reserve estimation, long-term mine planning, short-term mine planning, ore control and surveying. Technological advances, including powerful personal computers, applicable mine planning software and surveying instrumentation, have become readily available and affordable. The computerized ore control procedures used at Copperstone include sample data collection, laboratory automation and computerized data management. These have reduced the time to complete ore control on a blast pattern by 50% to 75%. The final product - ore control - is generated in a more timely and accurate manner.

Jan 1, 1991

By F. -J. Wodopia

Sustainability of energy supplies has been an issue of general interest for a long time. Whilst in the past the continuous productive use of natural commodities was in the fore, its compatibility with the environment and climate and ultimately also social aspects have recently gained more and more attention. Today many discussions focus on the climate compatibility of individual options to act. Fossil fuels, in particular coal and lignite, are generally challenged because coal use makes a significant contribution to global man-made CO2 emissions. The drastic increase in the consumption of fossil fuels is not explained by the fact that coal utilisation technologies are not or cannot be sustainable but rather by the growing world population and the endeavours numerous national economies trying to catch up economically. Coal is the world’s No. 1 fuel and, in the view of many experts, will keep this position also in the foreseeable future. The access to its deposits plays a significant role for the economies of the emerging countries. Consequently the aspects of energy security and economic efficiency need to be considered at eye level with climate compatibility. In Germany, however, the public acceptance of fossil fuels and of large industrial projects is in the focus of attention.

Jan 1, 2011

In 1991, US mine production of barite decreased 3.4%. Barite consumption, sold or used by grinding plants, decreased by 11.7%. Imports also decreased by 15.4% over 1990. World mine production increased I%, according to the US Bureau of Mines. The value of domestically produced barite, f.o.b. mine, increased 3.3% according to the Bureau. The declared value c.i.f. US port of all imported crude barite during 1991 increased from $40.61/t ($36.84/st) in 1990 to $42.35/t ($38.42/st), the Bureau stated. Nevada was the leading producer of barite with 78% of the total, followed by Georgia and Missouri. It is estimated that 75% of the domestically mined barite was used as a weighting agent in drilling fluids. The remaining 25% was used in barium chemicals, glass or as a filler. Most of the production from Missouri, Georgia and Tennessee was used in the non-oilfield sector. Of the total barite used by grinding plants and chemical manufacturers, it is estimated that 93% was used in drilling fluids. The remaining 7% was in the non-oilfield sector, including barium chemicals and fillers in paper, plastics and glass. Tonnage consumed in the drilling fluids market decreased due to the lower average rig count during 1990. The average number of rotary rigs operating was 860. That was 14.9% less than the 1990 average of 1010 in the US. Crude barite imports were 138 kt (152,000 st) less than 1990 or 15.4%. Imports accounted for 70% of the (ap¬parent) barite consumed in the US. During 1991, China continued to be the leading exporter of crude barite ore to the US with 85.1 %. India followed with 14.8%. About 97.5% of the imported barite ore was used in the oilfield sector. Ground barite imports decreased from 56.7 to 46.2 kt (62,500 to 51,000 st) 1991. Mexico was a major exporter to the US, accounting for 75.3% of the total ground barite imports. Canada shipped 23.7%, while other countries accounted for less than 1 %, primarily for the nonoilfield market. During 1991, the number of grinding plants supplying the drilling fluids market along the Gulf Coast was reduced from 12 to 10. Baroid Drilling Fluids completed its mining program at the Rossi Mine near Dunphy, NV.

Jan 1, 1992

By Akihiro Higashide, Roy H. Patten

The DOT Tunneling method combines two conventional earth pressure balance shield machines in an overlapping cylindrical arrangement. The method allows two tunnels to be driven simultaneously with mini¬mum cross sectional area. Two full size trials, one configured horizontally and one vertically stacked, were successfully completed employing the DOT method. The method was then utilized for the new transportation system. The goggle-shaped DOT machine, 9.36 m high by 15.86 m wide, is the largest earth pressure balance shield machine in the world. This paper includes a general description of the DOT tunneling method as well as a history of its development.

Jan 1, 1995

By Johan K. Rodenburg

A major bauxite belt was discovered and evaluated from 1969 to 1974 by P. T. Alcoa Minerals of Indonesia in West Kalimantan, Indonesia. The proven reserves of beneficiated bauxite are 800 million tons averaging 38.6% AA1203 and 3.0% RSiO2. Inferred reserves of washed bauxite are in excess of 2 billion tons. The bauxite occurs as capping of low lying hills which were formed during the post Paleogene peneplaination stage. The overburden varies from 0.6 to 3.8 meters and the nodular bauxite horizon from 2.2 to 5.2 meters. The deposits were formed by the in situ weathering of predominantly acidic and basic intrusive rocks.

Jan 1, 1984

By Brendan Demich, Joseph McGuire, Emily J. Haas

Near misses recorded and reported by workers can provide awarenessto the potential causes of injury and prompt safety management initiatives. Although most companies require near-miss reporting, it is unclear what the value of these reports are, if any, and how they influence subsequent actions or controls to reduce on-the-job risks. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a case study with an aggregates company in which near-miss reports were analyzed at each of their locations over an entire quarter during the summer of 2018. Within that quarter, workers recorded 249 near misses. Of those, 167 were valid near misses that occurred at work. Researchers coded the reports using a qualitative 5 × 5 risk matrix. Of the 167 near misses, 19% were deemed low risk, 25% moderate risk, 30% high risk, and 26% critical risk. Several patterns in the near-miss incidents were documented, including classification of incidents and common corrective actions referenced (i.e., elimination/substitution, engineering control or redesign, work process/procedures, and personal protective equipment). The analysis provides insight into ways that risk communication and management programs can be improved to reengage workers and their situational awareness on the job.

The world's largest hydraulic excavator was recently introduced at Syncrude's North Mine at Fort McMurray, Alberta, in Canada. O&K's 826t (910-st) behemoth RH400, with a 42-m3 (55-cu yd) bucket, is capable of loading 72.5 t (80 st) in one pass. Syncrude's Alberta operation is the nation's largest single source of crude oil. It is also the world's largest producer of oil from oil sands. Syncrude produces 205,000 bbl/day, expects to increase production to 225,000 bbl/day by 1999 and to 320,000 bbl/day by 2005. That translates to 73.5 million bbl of Syncrude Sweet Blend (SSB) produced in 1996, 82 million bbl in 1999 and 114 million bbl in 2005. The North Mine is a new development that will replace the current East Mine, to be depleted of oil sand by the end of 1999. The North Mine will feature hydrotransport, a new and unique method of transporting oil sand from the pit to the process plant. Oil sand from the truck-and-shovel operation will be processed through a double-roll crusher and placed in a cyclofeeder where it mixes with hot water. The material is then screened and transported by pipeline to the extraction plant. Hydrotransport will replace conventional conveyor transport for moving raw product from the pit. Mine development will also use two 290-t (320-st) haul trucks to compliment the fleet of existing 218-t (240-st) trucks.

Jan 1, 1998

By K. J. Reid, I. Iwasaki, T. Sabelin

Introduction Occurrences of platinum group minerals (PGM) in mafic and ultramafic rocks in association with Cu-Ni mineralization are well known. Yet for the Duluth Complex, a large body of dominantly mafic igneous rocks in northeastern Minnesota with significant Cu-Ni mineralization (Bonnichsen, 1972; Boucher, 1975; Watowich, 1978; Weiblen and Morey, 1980), little has been published concerning its platinum group element (PGE) contents and mineralogy. In a previous study of massive sulfide rock, sperrylite (PtAs2) was found in nickel arsenide and recovery of arsenide minerals by flotation has been investigated (Iwasaki et al., 1986; Ryan and Weiblen, 1984). Recently, an announcement was made of the discovery of significant quantities of platinum and palladium [peak assay values of 9 g/t (0.27 oz per st)] in an interval of a drill core with disseminated sulfide mineralization 16 km (10 miles) southeast of Ely, MN (Anon, 1985; Sabelin, 1985). This paper describes PGM from the Pt-Pd-enriched zone and evaluates their potential for concentration. Geologic setting The Pt-Pd zone occurs in the South Kawishiwi in¬trusion near its basal contact at 734 to 737 m (2408 to 2418 ft) depth. The South Kawishiwi is one of several minor mafic intrusions that constitute the western margin of the Duluth Complex near Ely, MN (Fig. 1). It is com¬prised of a 70.1- to 350.5-m (230- to 1150-ft) thick sul¬fide-bearing basal unit of troctolite with minor amounts of anorthosite, norite, picrite, and oxide layers overlain by a troctolite unit with interlayered anorthosite (Bonnichsen et al., 1980; Foose, 1984; and Foose and Weiblen, 1986). The basal unit, in which the Pt-Pd zone is found, is markedly heterogeneous in rock type, lacking any coherent internal stratigraphy, and shows evidence of both pre- and post-consolidation faulting (Foose and Weiblen, 1986). Geochemistry Chemical analyses were made on 0.3-m (1-ft) intervals of crushed drill core material (1/4 core, BX size) at 731.5 to 740.7 m (2400 to 2430 ft) depth and the results are presented in Fig. 2. The analytical techniques used were atomic absorption spectrometry for silver, chromium, copper, and nickel; a coulometric titration method for sulfur; and a combined fire assay-DC plasma technique for gold, palladium, and platinum. Figure 2 shows the significant enrichment of platinum and palladium at 734 to 737 m (2408 to 2418 ft) depth; it corresponds to a stratigraphic interval rich in oxide minerals. Average values for platinum and palladium contents over the 3-m (10-ft) interval are 2520 and 2580 ppb, respectively, or 5.1 g/t (0.15 oz per st) platinum plus palladium. Platinum plus palladium contents from individual 0.3-m (1-ft) intervals are as high as 9120 ppb or 9.1 g/t (0.27 oz per st) and average 7.4 g/t (0.22 oz per st) in a 1.5-m (5-ft) interval in the richest part of the zone. The Pt-to-Pd ratio is nearly 1:1 over the entire 9.1-m (30-ft) interval and the platinum and palladium correlate closely with chromium, which ranges from 1.9% to 5.3%. Copper, nickel, and sulfur contents for the drill core interval are also given in Fig. 2. In¬terestingly, the Pt-Pd high corresponds to a depletion in copper, nickel, and sulfur. Mineralogy of the Pt-Pd zone The Pt-Pd zone occurs within an oxide-rich zone or layer that consists essentially of oxide minerals, plagioclase, and olivine. The oxides may constitute as

Jan 1, 1987

In 1992, United States mine production of barite decreased 8.5%. Barite consumption, sold or used by grinding plants, decreased by 36.9% and imports decreased by 61.6% vs. 1991. World mine production decreased 1.5%, according to the US Bureau of Mines. The value of domestically produced barite, f.o.b. mine, decreased 11.9% according to the Bureau. The declared value, c.i.f. United States port, of all imported crude barite during 1992 decreased from $42.35/t ($38.42/st) in 1991 to $40.09/t ($36.37/st). Nevada continued to be the leading producer of barite with 88% of the total, followed by Georgia and Missouri. It is estimated that 80% of the domestically mined barite was used as a weighting agent in drilling fluids. The remaining 20% was used in barium chemicals, glass or as a filler. Most of the production from Missouri, Georgia and Ten¬nessee was used in the non-oilfield sector. Of the total barite used by grinding plants and chemical manufacturers, it is estimated that 90% was used in drilling fluids and 10% in the non-oilfield sector. This included barium chemicals and fillers in paper, plastics and glass. The tonnage consumed in the drilling fluids market decreased due to the lower average rig count during 1992. The average number of rotary rigs operating (717) was 16.6% less than the 1991 average of 860 in the United States. Crude barite imports were 518 kt (571,000 st), 61.6% less than in 1991. Imports accounted for 44.7% of the barite consumed (apparent) in the United States. During the year, China continued to be the leading exporter of crude barite ore to the United States with 67.2% of total crude ore imports. India followed with 31 %, and others with 1.8%. About 90% of the imported barite ore was used in the oilfield sector. Ground barite imports decreased from 46.3 kt (51,000 st) to 30.9 kt (34,100

Jan 1, 1993

By T. O. Llewellyn

The Bureau of Mines, U.S. Department of the Interior, conducted studies to recover phosphate from four dolomitic southern Florida deposits not currently mined. The samples contained 5.8 to 10.2 percent P205 and 1.7 to 1.8 percent MgO. Chemical analyses of sized fractions indicated that no pebble concentrate (plus 1.2 mm) could be produced from these samples. A scheme was developed that consisted of desliming, grinding, scrubbing, and redesliming the ore to produce a flotation feed. Conventional one-step fatty acid-fuel oil batch flotation tests on the samples resulted in concentrates containing 29.0 to 31.3 percent P205 at flotation recoveries ranging from 72.4 to 96.1 percent of the flotation feed. The MgO content of the concentrates ranged from 0.47 to 1.36 percent. Continuous flotation of the Manatee No. 2 sample indicated that commercial-grade phosphate concentrates analyzing 31.3 percent P205 and 0.55 percent MgO could be produced with a flotation recovery of 89.9 percent. The MgO content of concentrates obtained from the Manatee No. I and Hardee samples was 1.20 to 1.36 percent, respectively. Leaching with aqueous SO2 reduced the MgO content of these phosphate concentrates to 0.5 and 0.8 percent, but with a concomitant loss in phosphate recovery.

Jan 1, 1983