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By M. C. Rockwell, G. F. T. Lay

Promising placer gold exploration sites offshore Lunenburg County are drowned pre- and post-glacial river channels and auriferous glacial tills. Gold values up to 5.67 9/m3 have been encountered in the vicinity of the Ovens Peninsula offshore Lunenburg County. Moderate gold values associated with notable amounts of heavy minerals were reported from various other exploration sites in this area. This paper highlights the major geological and gemorphological features for placer gold depositions in southern Nova Scotia. The past to present gold exploration activities nearshore and offshore Lunenburg County are summarized and potential areas for placer gold identified.

Jan 1, 1988

By Ravi Shah, Augusto Lucarelli, Daniele Peila

"In mechanized tunneling the annular gap between the segmental lining and the surrounding soil caused by tunnel driving, must be backfilled almost instantaneously with an adequate grouting mortar. The objective of this research is to perform a fully three dimensional modeled parametric study using FLAC 3D and evaluate the effects of backfill grouting on the tunneling performance. The research focuses on comparisons between different injection materials and state-of-the-art Bi-Component grout and their effects on the settlements on the surface. The research consists of testing a regular situation of tunnel excavation using a shielded machine with face under pressure. The tunnel dimensions and the soil properties are selected as close as possible to the reality and based on Turin Metro case. 1 INTRODUCTION Excavation of tunnels in urban areas can induce ground movements, which have negative effects on existing structures. In such scenarios, shield tunneling has become a well-accepted construction method in various ground conditions. It is characterized by relatively complex interactions between the soil, the tunnel boring machine (TBM) itself, the tunnel lining and the tail void grout. The problem to control the settlement depends on the face pressure, ground properties and back filling procedure and material of the tail void. The face pressure acts against the front to guarantee the face stability. In case of EPB TBMs the stability of the tunnel face is ensured through the excavated soil itself, which is conditioned and is maintained in compressed state within the excavation chamber. When excavating with TBMs a tail void is created between ground and the lining (Fig.1) after the TBM excavation and ring assembly that must be backfilled instantaneously by injecting the backfill material through the TBM’s tail shield. The process is of primary importance as it reduces the surface settlements and creates an immediate link between the ground and lining, sealing against ground water and leakage, reducing the differential movements between segments and providing long-term stability. The most used backfilling materials are: Inert mixtures that do not contain cement instead sometimes they are replaced by fly ash or other substitutes. A typical design of an inert mortar consists of sand, fly ash, bentonite and water. Pea gravel, which is constituted of granular materials with grain size ranging from 8 to 12 mm. This mixture is highly recommended for tunnels being constructed in rock mass with little deformation rates.Cement mortar is composed of cement, water, aggregates and sometimes bentonite. Cement controls the principle mechanical property of the mix, which can reach high values of 15-20 MPa in 28 days. The aggregates contribute towards the shear strength and reduce the pumpablity of the mix (Thewes and Budach, 2009). The reduced active systems have a cement content of 50-100 kg/m3, whereas the active system the binder component derives full hydration with cement content of over 200 kg/m3 ."

Jan 1, 2016

By William H. Engelleitner

Agglomeration by balling in cylindrical or shallow pan devices dates back to the early part of this century. The first sintering tests conducted by Dwight-Lloyd on nonferrous ores included a mixing step for ore, flux and fuel carried out in a deep pan device similar to the balling pans, or discs, presently in use. Further work directed mainly toward sintering of ferrous and nonferrous ores always included a preparatory step, usually referred to as mixing, agglomerating or green-balling of the ingredients. In the late forties and early fifties two methods of particle preparation prior to firing were in general use. In Europe the balling pan was used predominantly, both as a mixer and as a pelletizer. In the United States many pilot plants and semi¬commercial plants used balling drums. When the first iron ore pelletizing plants were built in this country, the most frequently used device for green-balling was the cylindrical drum. At the same time, the pan device was used both in Europe and the United States for many other materials such as fertilizer, cement, flyash, alumina and copper concentrates, as well as to mix the feed for sinter machines. The difference between these two balling devices - -the drum and the disc - has been the subject of much discussion and is well covered by several papers included in the 1962 publication "Agglomeration' issued by AIMS, based on their 1961 International Symposium held in Philadelphia. (1)

Jan 1, 1965

By C. Y. Haas

Of all the industrial clay minerals, attapulgite probably enjoys the widest variety of applications. A review published over three years ago by Haden and Schwint (18) cited some 80 individual uses, a list which continues to grow. In its near half-century of commercial life, attapulgite has received a generous share of research study and patent development effort, both on the part of producers as well as consumers. This work has been divided between understanding the mineral's structure or properties and applying it to specific end-uses. Naturally, information gained from the former has pointed toward opportunities in the latter. References of particular significance are cited throughout the text. Attapulgite's variety of uses derives from the unique three-dimensional structure and needle-shaped particle form of this crystalline hydrated magnesium aluminum silicate. Its inherent colloidal and sorptive properties are well known, and distinguish it from its sister clay minerals. Attapulgite is characterized by its high surface area, porosity, sorptivity, and decolorizing power. Its slips or slurries are viscous and thixotropic, however, unlike bentonite are not flocculated by electrolytes. In Table I are compared the general properties of attapulgite, bentonite, and kaolin. The properties in Table I are documented in greater detail by the wealth of scientific literature which has been published on the composition (14)(15), structure (6)(16), surface (16)(4)(22)(24), adsorption (31)(4)(5)(25), rheology (10-11)(12)(13)(26)(27)(32), plasticity (30) (31), and chemistry (23)(3)(7) of attapulgite. Attapulgite is the principal mineral constituent (70 to 80%) of attapulgite clay as it is commercially produced in the Georgia-Florida area of the United States. As mined, this clay also contains 10 to 1S% montmorillonite, sepiolite, and other clays; 4 to 8% quartz, and 1 to 5% calcite or dolomite. (18) During processing, non-clay fractions are removed so that commercial products are enriched to 85 to 90% attapulgite. By wet processing (such as practiced in the

Jan 1, 1971

By Charles F. King

THE only investigations on record of the reactions occurring during the Bessemer blow are of charges containing a large percentage of manganese, with the exception of two partial analyses by Snelus and Barker of the. English method, where a low percentage of manganese was used. They do not give the analysis of the spiegel, nor do they report any graphitic carbon after the first stage of the process. Both report only traces of manganese after the first stage until the addition of spiegel. The slags corresponding to the samples of metal were not analyzed.

Jan 1, 1881

By I Ritchie, G Lane, C Morley, D Yataco

Marcobre SAC (Marcobre) is developing the Mina Justa project in Peru. The project has a lower grade oxide orebody overlaying the higher grade sulfide orebody. The oxide ore is treated by acid leaching; consumption of acid is high and is managed by vat leaching rather than the more conventional heap leaching process.The leaching process uses ore crushed to 100% passing 8 mm to optimise copper recovery. Acid consumption generally increases with a higher proportion of fines. Marcobre is investigating a three-stage crushing circuit with high pressure grinding rolls (HPGR) in the third stage, instead of the more conventional four-stage cone crushing circuit. The use of HPGR can result in higher fines production due to the higher compression forces in the crushing zone. This paper reports on the outcomes of the test work completed by Marcobre in 2016 and 2017 to manage fines production and compare the use of HPGR with conventional crushing on a high acid consuming ore.At moderate pressing forces, a HPGR crushing circuit appeared to produce similar size distributions to cone crushing. On average, both the copper recovery and the acid consumption in subsequent vat leaching were higher with HPGR crushing than with cone crushing.CITATION:Lane, G, Morley, C, Yataco, D and Ritchie, I, 2017. Are there differences in size distribution when comparing conventional crushing and HPGR?, in Proceedings MetPlant 2017, pp 60–72 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By Morgan M. Sears, Mark Van Dyke, Gamal Rashed, John Rusnak, Khaled Mohamed

"In 2016, room-and-pillar mining provided nearly 40% of underground coal production in the United States. Over the past decade, rib falls have resulted in 12 fatalities, representing 28% of the ground-fall fatalities in U.S. underground coal mines. Nine of these 12 fatalities (75%) have occurred in room-and-pillar mines. The objective of this research is to study the geomechanics of bench room-and-pillar mining and the associated response of high pillar ribs at overburden depths greater than 1,000 ft. This paper provides a definition of the bench technique, the pillar response due to loading, observational data for a case history, a calibrated numerical model of the observed rib response, and application of this calibrated model to a second site. INTRODUCTION Bench mining is a an underground mining technique typically applied to room-and-pillar mines where full seam extraction on development presents an unacceptably high risk of injury from high pillar ribs or where the mining equipment is not designed to extract the full seam thickness. To mitigate the increased risk associated with high ribs and slender pillars, a more modest thickness is extracted from the top of the seam on development. This is followed by grading the floor and recovering the bottom of the seam with or without extraction of the pillars during retreat mining. A mine located in Eastern Kentucky extracts two seams at depths ranging from outcrop to 2,000 ft. In some areas of the mine, Seam A and Seam B are close enough together to be mined simultaneously. Seam A (top) is mined on development 7 to 9 ft. high for the entire length of the panel. On retreat, as each pillar is extracted, the continuous miner is ramped down into the floor (Seam B), two pairs of Mobile Roof Support (MRS) units are set, and the pillars are extracted at the full mining height of 14+ ft. During the pillar recovery process, the floor is extracted in each entry, from a ramp initiated outby the retreat line, sequentially just prior to extracting the lifts from the pillars (see Figure 1)."

Jan 1, 2017

By P. Archer

The Blondeau Formation has been examined in a stratigraphic drill section at Barlow Lake. The formation contains pyroclastic flows and volcanogenic sediments throughout, but epiclastic sedimentary rocks dominate the upper parts of the section. Five distinct types of pyroclas tic flows are known in the section, as well as minor mafic lava flows. Volcanogenic sediments are commonly intercalated with the true volcanic rocks. Sedimentary rocks include fine-grained intraclastic sandstones, heterolithic sandstones and green and black shales. Interpretation of the origin and relative disposition of the volcanic and sedimentary rocks favours a model of near-emergent vulcanism in an upward shoaling environment.

Jan 1, 1984

By . Adolfo Farfán C

El presente trabajo describe los problemas ocasionados por los incendios en la mina de Cerro de Pasco. Si bien es raro que se origine un incendio en minas de características especiales como la de Cerro de Pasco, no se descarta la posibilidad de un corto circuito o algún otro infortunio. Por ello, es necesario conocer las causas, zonas de vulnerabilidad, los métodos de minado, ventilación, los antecedentes del incendio, origen, combate, las cuadrillas de rescate minero y la prevención de este desastre.

Nov 20, 1978

By Kenneth Etschlager

The ISEE Blast Vibration and Seismograph Section provides a forum for the discussion of issues related to vibration and noise from mine, quarry and construction blasting. The section began as a Technical committee in 1995 to promote the accuracy of blasting seismographs. Currently five subcommittees exist within the section: Seismograph Standards; Seismograph Testing and Calibration; Vibration Limits, Technical; Vibration Regulations; and Program and Communications. Foremost, the Seismograph Standards section wrote the first two technical standards adopted by the ISEE. The historical accomplishments, current activities and objectives of the section are discussed.

Jan 1, 2003

By Ammar Henchiri, Godfrey McDonald

"Breakwater Tunisia S.A.’s Bougrine mine is located in a semi-arid region of Tunisia characterized with Triassic salt domes. Due to extensive agricultural land-use in the mine area, a zero-discharge tailings facility design and high water recycling rates to the concentrator were chosen to minimize the environmental impact to the surrounding area. The process water supply has an accumulation of naturally occurring salts due to high evaporation rates and the need to recycle 70% of the process water. The elevated salt content of the process water had an adverse effect on the efficiency of the flotation reagents, which led to the production of lower quality zinc concentrate.The impact of the water salinity on the zinc concentrate quality was documented by extensive laboratory testing. A feasibility study was prepared and a decision was made to install a reverse osmosis plant for desalination of the process water. A plant was constructed during 2000 which currently supplies up to 85 m3/hr of de-mineralized water, equal to approximately 45% of the total process water requirement. The salinity of the process water decreased from about ten to twelve grams per litre before installation to less than three grams per litre. Together with minor modifications to the concentrator circuit, Breakwater Tunisia has increased the zinc concentrate grade from 50% zinc to 55% zinc without compromising the zinc recovery rate of approximately 84%.This paper discusses the successful installation of a reverse osmosis desalination plant that allowed Breakwater Tunisia to improve the grade of the Bougrine mine zinc concentrate and thus increase the net smelter return.INTRODUCTIONBreakwater Resources Ltd., through a wholly owned subsidiary, Breakwater Tunisia S.A., acquired the Bougrine underground mine and related assets in September 1997. During the winter of 1997/1998, the company rehabilitated the mining equipment, modified the concentrator circuit, developed a new mine ventilation system and prepared a new mining production program. The mine was reopened on May 2, 1998 and was in commercial production as of June 1, 1998."

Jan 1, 2003

By Benjamin W. Haynes

As part of the first-order assessment of potential manganese nodule processing reject waste materials, the Bureau of Mines estimated the physical and chemical characteristics of reject waste materials that would be generated from each of five potential process flowsheets. These processes were chosen because of their economic and technical feasibility for first-generation nodule processing. A brief description of the five processes is given to show process inputs and outputs, The physical characteristics are predicted based on land-based laterite processing where applicable, and where no land-based analog exists, on the basis of process chemistry. The probable chemical characteristics such as element content and compound form are tabulated for each process for 16 elements: As, Ba, Be, Cd, Go, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, TI, and Zn. These elements were chosen based on their presence on the toxic substance list of priority pollutants, EP toxicity criteria, and major and minor elements of economic importance (Co, Fe, Mn, and Mo). Physical and chemical analyses as well as results of the EP toxicity test of one industrially supplied pilot plant reject waste material are presented.

Jan 1, 1982

By S Brochot, M-V Durance

In many cases, current metallurgical accounting practice does not consider the errors associated with the measurements used in obtaining the metal balance. Considering all measurement errors, including errors associated at each step of the process - from sampling and analytical errors to measurement errors in circuit instrumentation, can improve the accuracy of the final metal balance - assisting in the improvement of process performance, optimisation and control.The consequences of the inclusion of measurement errors on metal balance for different circuit configurations and typical metallurgical accounting practice (two product and three product formulae) will be discussed in this paper.Examples of the tools, methodology of implementation, and periodical metal balance tasks are presented to illustrate the advantage of this approach in meeting the different requirements of each department.CITATION:Brochot, S and Durance, M-V, 2012. A new approach to metallurgical accounting, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 217-224 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By J Zhou

Gold in sulfide ores is associated predominantly with sulfide minerals and occurs as both microscopic and submicroscopic particles. In non-refractory sulfide ores, gold occurs mainly as coarse- and medium-grained particles. Minute inclusions and submicroscopic gold usually account for a minor portion. In contrast, gold in refractory sulfide ores occurs mainly as minute particles and submicroscopic gold, and microscopic gold usually accounts for an insignificant portion. In gold ores containing carbonaceous material, the preg-robbing nature of carbonaceous material may impose challenges on gold extraction and cause gold losses. To extract gold from refractory sulfide ores, the ore needs to be finely ground and preoxidation is often required. Sulfide host minerals must first be oxidised to create a porous structure through which the cyanide leach solution can penetrate to reach the colloidal gold particles. The oxidation is traditionally achieved by roasting, autoclaving or bacterial oxidation. In carbonaceous sulfide ores exhibiting a preg-robbing nature, the carbonaceous material needs to be treated by roasting, autoclaving or other means to minimise the preg-robbing effect. As a predictive and troubleshooting tool, the gold deportment study plays an important role in gold metallurgy. It determines the deportment of gold in an ore or mill product and identifies the mineralogical issues that may affect or may have affected gold extraction. The information acquired from a gold deportment study can be used to assist in process selection, flow sheet development, recovery improvement and reagent optimisation.CITATION:Zhou, J, 2013. Deportment of gold in sulfide ores and implications for gold extraction, in Proceedings World Gold 2013 , pp 433-442 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By F. Calizaya

This study summarizes the ventilation requirements for a highly mechanized P.T.Freeport Indonesia's underground mine operation in Irian Jaya, Indonesia. The Deep Ore Zone (DOZ) is a copper-gold deposit being developed underneath the current Intermediate Ore Zone (IOZ) mine. One of company's current plans is to prepare this mine for a steady oreflow of 25,000 tpd by year 2003. This study includes the estimation of airflow requirements for various mining activities, the design of major intakes and returns, the determination of airway resistances and specifications of fan duties. It also includes the results of air pressure/quantity measurements in existing airways and the standards stated by the current Indonesian mining law.

Jan 1, 1998

By M. R. Paterson, M. K. Suddaby

Operational and economic factors tend to favor the application of continuous processes in preference to batch processes in the majority of mineral processing applications. In this paper, the requirement for a continuous elution process is established and the development of a large-scale pilot plant is described. It is based on a continuous elution apparatus that has a number of special features. These are the subject of various patent applications. The apparatus is suitable for adaptation to the AARL, Zadra, and other methods of elution. The performance of the atmospheric continuous elution system (ACE) is concluded to have significant advantages over the batch process.

Jan 1, 1988

By John Reilly

Traditional methods of project procurement of have remained virtually unchanged in the U.S. infrastructure construction industry for more than 50 years. The traditional method, Design-Bid-Build (DBB), uses a two-step process that separates planning and design from construction. Design is generally done by the public agency and their consultants and the subsequent construction contract is procured from the private sector, almost always by a “low-bid” approach. This method has worked well for many projects, delivering quality work for the lowest bid price. This is particularly true for those projects where the work, and the public agency’s management procedures, are well understood by the contracting community and there is relatively low uncertainty in the work or conditions, particularly geotechnical conditions for underground construction. However, concerns exist with the DBB process. It is time consuming because all planning and design work must be completed prior to beginning any construction work and it is of concern for complex or large projects, plus those with significant risk, where the separation of design and construction, in conjunction with pressures resulting from the low-bid environment, often result in substantial cost and schedule increases. Frequently, these increases occur in a non-productive, inefficient, adversarial work environment leading to claims, disputes and costly litigation (Quick 2002).

Jan 1, 2007

By Ralph E. Weeks

Utilization of true in situ technologies for mining copper in Arizona will involve a complex environmental permitting process. This process is a key factor in determining the feasibility, costs, and implementing time frames required for development of this innovative mining method. The regulatory structure in Arizona is presently changing due to enactment of the Environmental Quality Act (EQA) of 1986 and development of new aquifer protection rules and regulations. The Bureau of Mines has reviewed the comprehensive hydrogeologic characterization, ground water monitoring, mechanical integrity testing, well construction, contingency planning, and other regulatory elements that will serve as mechanisms to assure protection of ground water resources. The purpose of this paper is to inform the domestic copper industry of the significance of the new Arizona regulatory structure and its implications for prospective in situ operators.

Jan 1, 1988

Jan 1, 1985

By S. A. Scott

Mintek developed the MinataurTM leach-solvent extraction-precipitation technology as a cost effective, easily operated alternative to conventional gold refining processes. The technology was first commercialized at the Harmony Gold Refinery in 1997 to produce 99.99 per cent gold product and has subsequently led to development of various value-addition steps including the casting of various investment bars, gold wire drawing and gold potassium cyanide powder production. In addition to refining gold to high purity, if an appreciable amount of silver is present in the feed material it is also refined to 99.99 per cent purity. The major advantage that the Minataur? technology has over other gold refining processes is the relatively low gold lock-up and reduced operating costs. The operating cost1as at April 2001 for the expanded Harmony refinery (24-ton per annum gold production) was approximately half that of conventional smelting and toll refining. The extractant employed for solvent extraction is relatively cheap and highly selective for gold, making the technology attractive in situations where significant quantities of platinum group metals or base metals are present.

Jan 1, 2004