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By Gordon F. Revey, Dan Harrison

Hanging Lake Joint Venture recently excavated two conventional 12.8 m (42 foot) diameter highway tunnels in the difficult ground conditions of Glenwood Canyon, Colorado. This paper outlines the type and success of the various Controlled Blasting Techniques that were used to minimize overbreak in the portal and tunnel excavations. The different Smoothwall and Cushion Charge loads used in the different ground types are described in detail. Delay Timing and Drilling Pattern variations are also discussed.

Jan 1, 1991

By Daniel W. Kappes

In late 1995 at the Randol symposium in Squaw Valley, I gave a paper which described the Itos project flowsheet. At that time, project construction was nearly completed and stmtup was close. This paper describes the ltos operation since then. To summa­rize things, startup occurred partially in late 1995 with full start­up of all components in about mid 1996. From then until now, April 1998, the plant has been running at partial capacity and has yet to achieve full production rates.

Jan 1, 1998

By S. K. Singh, J. Shepherd

Feather-edging, a major source of injury and fatal accidents in Australia, South Africa and the United States, refers to a phenomenon in which the roof at the goaf edge falls, often suddenly, as a thin wafer of rock that overrides conventional timber breaker lines. The fall may adversely affect a working bord at a distance of 15 m (50ft) or more from the goaf edge. Feather-edging typically occurs in relatively massive, strong roof strata such as sandstone or conglomerate. This paper presents the results of a test in which a concentrated row of fully grouted bolts were used to prevent feather-edging in an Australian pillar- ("total-") extraction coal mine. The test demonstrated that the bolts could resist feather-edging.

Jan 1, 2000

By J. D. Pfarr

The Homestake Mine, located in Lead, SD, has been in business for 113 years. Until 10 years ago, conventional mining methods were used to extract ore. Due to complexities in the ore bodies and increasing costs, new technology was introduced to the mine. An integral part of this technology was mechanized cut-and-fill mining. This mining method currently produces about 50% of the annual production and has proven to he safe and economical. As a result, the Homestake Mine remains competitive in today's market.

Jan 1, 1992

By P. J. Brown, R. W. Nice

The Thalanga Copper-Lead-Zinc Concentrator in Northern Queensland was commissioned in early 1990. The design of a flotation process for the sequential production of separate copper, lead, and zinc concentrates has always been a most formidable mineral processing challenge. In 1988-1989 during the process design phase, sized fractions of various samples were subjected to quantitative and qualitative mineral analyses. These analytical techniques are collectively known as modal analysis. Modal analysis aided in the selection of key process treatment parameters for the initial laboratory testwork on the Thalanga ore. The work also guided the flowsheet development and quantified the mineralogically imposed limitations on the separation process. This paper describes in general terms how these modal techniques were used to guide the program of laboratory flotation testwork which constituted the flowsheet design phase of this project. During these design studies, the primary grind and regrind requirements were deduced and the basic flowsheet configuration selected. Recent operating plant performance data are to illustrate the value of modal methods in addressing complex metallurgical separation problems.

Jan 1, 1995

By Richard M. Crowell, John W. Shield

GeoBiotics has developed a biooxidation technology (patents pending) which involves coating refractory precious metal sulfide concentrates onto a support material and biooxidizing the sulfides in a heap configuration. The concentrates are produced from low or high grade sulfidic refractory ores or existing mine tailings. The process has been found to achieve high gold recoveries asso­ciated with stirred tank biooxidation, but at the low operating and capital costs associated with whole ore heap biooxidation. Improved gold recoveries of up to 98% after biooxidation are reported for 4 representative mines or deposits. The sulfide flotation concentrates were studied using 3 and 6 in. diameter columns or 3 in. drained vats. The refractory sulfide concen­trates biooxidize rapidly in 3 to 12 weeks with substantial increases in subsequent gold recovery.

Jan 1, 1996

By Krystyna Raszka, Jerzy Iskra

The paper presents results of spectrophotometric investigations concerning the adsorption of sodium oleate on silicon carbide in the presence of the cations of multivalent metals, applying the ATR IR technique with computer-aidedprocessing of the spectrum. The analysis of these spectra indicates the occurance of distinct OH and COOH bands in the pH range in which the hydroxy complexes of metals of the type MeOH+ and MeOH++ reach in the respective cases the highest concentration in the solution. The correlation of these results with those of flotation, measurements of the zeta potential confirms the proposed mechanism of activation of the flotation of silicon carbide, applying sodium oleate as a collector, the collection taking place over the adsorption of hydroxy complexes of the type MeOH+ and MeOH++

Jan 1, 1995

By J. L. Waldron

This paper presents a theoretical tool used to analyze gold recovery problems at Dee Gold Mining Co. The first step in addressing the problem was realizing that lower gold extraction was linked to high silver grades, and could not be correlated to either the carbonaceous or sulfidic content of the ore. Analyses of metallurgical testwork, blasthole, and mill recovery data demonstrated that decreases in gold extraction correlatP� well to increases in silver extraction. Figure 1 illustrates this for 1991 mill operations. This was the starting point for the work described in this paper.

Jan 1, 1992

By Ricardo Presnell, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Douglas N. Halbe

Large (> 100,000 oz.) sediment hosted disseminated gold (SHDG) deposits are often spatially associated with anticlines. Many SHDG deposits are within or closely associated with windows. Windows are erosional manifestations of fold culminations (4-way closed anticlines). Hydrocarbons are often trapped in fold culminations in the Canadian Rockies, and may account for degraded hydrocarbons in many SHDG deposits. In the Eastern Basin and Range Province, Mesozoic anticlines may have been large scale conduits fm gold bearing Mesozoic and Cenozoic hydrothermal fluids which became trapped and/or concentrated at the fold culminations.

Jan 1, 1990

By Johann Knecht

Due to lower specific investment and operating costs the tendency towards large scale equipment will remain. For the design engineers not only the stresses in the mill structure and manufacturing are of importance but also transportation to and erection on site. A scale up of the design of smaller sized units on the pantograph principle may not always give the best approach to the job in this respect. This paper covers recent developments in the design of large size equipment where the huge dimensions call for designs being different to the well known ball and SAG mill concept with cast conical endwalls. The first part describes the features of the biggest ball mill in the world, whereas the second part provides some details of the largest shell supported SAG mills being currently in the manufacturing process.

Jan 1, 1993

By Tim Haldane

Cyanide consumption at the Gold Fields Operating Company Mesquite Mine has shown a steady decline since the heap leach operation started up in 1986. A series of solution strength changes and equipment design improvements have resulted in a reduction of sodium cyanide consumption from peak levels above 1.0 pounds NaCN per ton of ore in 1986 to current levels at 0.15 - 0.20 pounds NaCN per ton of ore. Aside from the obvious cost benefits associated with this reagent consumption reduction, the property has also enjoyed environmental benefits which go hand-in-hand with these cost savings.

Jan 1, 1990

By Len H. Steele

To date VMD have designed, built and supplied nine autoclaves to various mining companies in Canada, the US, and Papua New Guinea. Initially, completely fabricated and lead lined units were shipped. The logistics of Placer Dome's Porgera PNG Project necessitated fabricating and lead lining each autoclave in five sections for transportation to site, each piece weighing approximately 30.5 tonnes. Support equipment such as turning rolls, automatic and manual welding machines had to be set up on site to facilitate assembly of these units which was a challenge in planning. This on site erection programme was completed in three months.

Jan 1, 1992

By James Y. Oldshue, Paul M. Kubera

Most coillillercial processing applications employing mixers in various types of slurry systems are continuous flow. These applications may also be multiple stage, with the stage number varying anywhere from two or three to ten or more. Two questions that usually come up at the beginning of any proposed pilot plant study are (1) can the pilot plant unit be operated batch-wise, and the results extrapolated both on the basis of scale and fluid motion to the full-scale tank which will be continuous-flow (and probably multi-stage), or (2) does the pilot plant need to be operated in a continuous-flow fashion, and if so, does the exact number of tanks/stages that are proposed for the plant need to be used in the pilot plant? We will consider these possibilities in sequence and present the principles involved in running some of the various pilot-plant arrangements.

Jan 1, 1992

By Charles A. Horne

Grinding mill circuits used for particle size reduction of mineral ores commonly use cyclones as primary classifiers. Typically, several individual cyclones are installed in a cluster (Fig. 1) where they can easily be added or valved-out of operation in order to balance classifier capacity with fluctuations in tonnage and recirculating loads as ore grades and hardness vary.

Jan 1, 1993

Political events during the past decade have caused businesses throughout the world to think globally. Countries once closed to free market enterprises are now open and seeking out foreign investment to help improve the well being of their populations. The mining industry has always been a global one. Today, though, the industry has become even more global. The driving forces behind this include the opening up of higher grade, lower cost mineral deposits in undeveloped and developing nations. In addition, permitting delays in the United States, coupled with stricter environmental guidelines and a general anti-mining attitude, have forced the mining industry to look outside US borders. The Mineral Economics and Management Society (MEMS) took as the theme of its seventh annual professional program "Economic Globalization of the Mining Industry." About 100 people attended the conference held in Arlington, VA in late March. Speakers included members of the investment community, academia, government and the mining industry.

Jan 1, 1998

By Cherie M. Tilley

Dynatec Mining Contractors (Dynatec) entered into a contract with Barrick Goldstrike Mines (Barrick) to develop the deep gold ore reserves at the Meikle Mine north of Carlin, Nevada. The Ventilation and Production Shafts were started in early 1994 and were completed in December, 1995. The mine development and mine construction programs were completed in November, 1996. This paper describes the Meikle Mine development program.

Jan 1, 1997

By William F. Riggs

The name of this symposium speaks for itself in the connotation normally assigned to the term 'political. "In this paper, various donors have contributed their stories of metallurgical bloopers, blunders, and scams. The paper covers areas from human error stories, through technical blunders, to outright scams. Included are some stories that involve geology as it relates to metallurgy, warehouses of precious metal concentrates, reagent selection, solutions that treat the symptoms instead of the problems, improper technological transfers, humorous design mistakes in the interest of being exacting, and many more. The stories are all true with the names and dates withheld and the cases presented in the true sense of the "John Doe Stories."

Jan 1, 2001

By S. S. Mauney

Natural and synthetic colors are used in almost every facet of daily life as a means of communication and expression. Natural ochres, umbers, hematites and magnetites were once used in their crude or semiprocessed state for their pigment value in construction products and low-end coatings applications. In recent years, though, they have yielded to synthetically produced iron oxides for more sophisticated products. Today, through innovative mining processing and marketing techniques, natural iron oxide pigments are once again gaining strong inroads into products and markets requiring precise chemical and physical characteristics. With the focus on environmental consciousness and resource conservation, value added natural iron oxides provide an economical and responsible alternative to color needs.

Jan 1, 1995

By M. S. Celik, G. Onal, S. Atak

The beneficiation of boron minerals flotation with well defined systems has been only slightly, investigated in the literature. The difficulty arises from fact that boron minerals cover a spectrum of solubilities. Colemanite (a calcium-containing, relatively insoluble, boron mineral) and borax (a highly soluble boron mine, have been used to exemplify the flotation of boron minerals. Using sodium dodecylsulfonate (SDS) and dodecylamine hydrochloride (DAH), the floatability responses of these boron minerals are considerably different. This has been ascribed to variations in the solubilities of boron minerals and the presence of cations in the lattice structure. In study, flotation tests and zeta potential measurements used to determine the flotation mechanisms of boron minerals.

Jan 1, 1994

By Tracy Braun, Dan Lampshire

Over the past decade, heap leaching at Cortez has evolved from a rather small operation producing around 30,000 ounces per year of gold to an operation scheduled to produce over 400,000 ounces in 2004. Evolution and expansions in the heap leach operations are discussed including plant design criteria and some of the design features in the various facilities. Operating parameters and production forecasting are also discussed.

Jan 1, 2005