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By Chee Theng

"What do you think are the most important topics in mineral processing today? It is a question that begs to be asked when more than 100 of some of the best and brightest in Colorado mineral processing and their invited guests are gathered in one room. They are there for the 66th Annual Colorado MPD Meeting held at The Broadmoor in Colorado Springs: three days of finely curated talks and social events where participation was strong, and information was exchanged and connections forged in a relaxed, informal atmosphere.Water, tailings and social licenseNot surprisingly, water management, with the associated issues of tailings and social license, was high on the minds of those present. The Mount Polley and Samarco tailings dam failures have had repercussions across the industry. “There are big challenges with respect to tailings, and social and environmental pressures to find better ways to treat them,” said Steve Hearn of Huntsman Corp., a view echoed by Bob Kilborn of Kilborn Group LLC. Metso Minerals director Keith Butler said, “Water conservation is a key issue today. Many mining activities are now located in remote areas, so it has social and economic impacts on mining operations.” For Brian Olson of Samuel Engineering, wastewater and reclaimed-water treatment is interesting.Fittingly, the first talk of the meeting was on dry stack tailings by Michael Blois of Takraf USA, who went over both the advantages and disadvantages. “The average now is over one tailings dam failure a year,” Blois said, “and that is one too many.” But the technology may not be the right fit for all projects. In his talk on the KSM project, Jay Layman, president and COO of Seabridge Gold, showed how it isn’t practical for KSM and how Seabridge reached the decision on a cyclone sand tailings managementfacility as the preferred management strategy.The luncheon keynote also dealt with a tailings pond spill, but of a different kind. Bob Schafer, chief executive of Eagle Mines Management, spoke on the federal missteps that led to the spill into the Animas River from the Gold King Mine, a mine that had been a dry mine throughout its life and up to the 1990s."

Jun 1, 2016

By Robert E. Mclvor

Classification system efficiency (CSE) is a simple metric that can be used to measure and increase ball milling circuit efficiency. It is defined as the percentage of the ball mill energy being used to grind target (oversize) particles. This paper describes CSE analysis conducted for a variety of operations with related improvements in circuit efficiency ranging from 3 to 30 percent. The achievable CSE for any given ball milling circuit is described, providing the means to determine the extent to which every plant can benefit from increasing grinding circuit CSE.

By Rambabu Pothina, Rajive Ganguli

The economics of a mineral-processing circuit is dependent on the numerous sensors that are critical to optimization and control systems. When a sensor goes off calibration, it results in errors that can have a severe impact on plant economics. Classical statistical approaches fail to detect when errors are “subtle,” unless they grow and become large enough to be “gross,” whereas methods based on signal processing and artificial intelligence fail in dealing with the complexity of process fluctuations. Due to the sheer volume of sensors, undetected errors are not remedied until the next calibration, which on average are a year apart across all industries [1]. This research aims to detect such subtle errors (2 percent bias) in shorter time spans of about a month — rather than wait for errors to grow — using innovative data-mining techniques and algorithms.

By Jerry C. Tien

The rare earth elements (REEs) are a group of 17 chemical (metallic) elements which appear in the periodic table. The group consists of 15 lanthanide elements along with yttrium and scandium (Table 1). They share many similar properties, which is why they occur together in geological deposits. Although commonly referred to as rare, they are really quite common; the reason they are perceived as rare is because it is not common to find them in commercially viable concentrations. These metals are critical to advanced technology, ranging from smart phones to global positions system (GPS) receivers, medical devices and jet engines. They are critical in green, high-tech and defense industries (Fig.1 and 2). Although there have been increasing efforts to find alternative supplies, these efforts have been complicated by the pollution that rare earth mining and processing creates. To extract rare earths minerals from mined ore is a complicated and costly process. The ore is first mined through normal mining process, the bastnaesite, which generally contains a number of minerals of little value, is first removed through a floatation process. The bastnaesite containing the REEs is further separated into their respective pure forms in a separation plant using acid and various solvent extraction separation steps. Each element has its own unique extraction steps and chemical processes. At times, these elements, in the form of oxides, will require reprocessing to achieve ideal purity. The last steps would be to further process into metals first, then alloys for various applications. The entire process takes approximately 10 days. The mining and processing of REEs, if not carefully controlled, can create environmental hazards. This is one of the reasons the Mountain Pass Mine in California was closed down in the 1980s.

Dec 1, 2013

By David Morrison

"The history of the mining industry is littered with in-pit crushing and conveying (IPCC), which should not be confused with the International Protocol for Carbon Capture, projects that failed. The failure is not the technical one of “did it achieve the desired tonnage rate for a longish test period” but, rather, the far more important one of “did it provide return on the investment in the manner that was promised?” While quite a few can claim the former, very few system installations can claim the latter.The reasons for the many failures are numerous, but they are all characterized by a combination of an element of engineering optimism in any, or all of the production rates, the productivity, or the operating and maintenance costs and in predicting the continuity of operating conditions. In these days of big data, propagating such a situation is rapidly becoming unforgivable.In this article, the three most common scenarios put to the corporate board for approval, and the logic as to why they were selected, are examined (with the irony included intentionally).• Fully mobile crusher, fed by a shovel and conveyed out of the pit to a waste dump / process plant.• Semimobile crusher (much more expensive than a fixed crushing station but which apparently allows trucks to short haul inside the pit and improve productivity), which moves when the face moves.• Relocatable crusher (more expensive than a fixed crushing station but which gets relocated at great expense after all the fixed infrastructure impeding relocation is demolished) fed by trucks that don’t leave the pit mostly.This paper will also consider the truth about their operational performance and associate costs."

Dec 1, 2016

By J. M. Barker

New Mexico is the leading domestic producer of perlite, a hydrated volcanic glass that can be expanded thermally to form a white, very porous, lightweight material. The United States is the leading consumer and producer of perlite in the world (Pettifer 1981). New Mexico produced, at five mines (Fig. 1), about 86% of all domestic crude ore mined in 1984 (Meisinger, 1985). Perlite is mined in 6 other western states, ore is expanded in 33 states, and the expanded ore is consumed in all states (Meisinger, 1985). Gross value of domestic ore mined in 1984 was about $16,500,000 (FOB mine; Meisinger, 1985) with much value added by expansion and processing prior to sale to end users. In contrast to the ubiquitous nature of perlite products in the U.S. economy, facilities for testing perlite ore, expanded perlite, and perlite products are notably lacking on a commercial, cost-effective, or readily accessible basis. The New Mexico Bureau of Mines and Min¬eral Resources (NMBM&MR) established a perlite¬testing facility in 1984 to mitigate this lack and to further the mining of perlite in the state.

Jan 1, 1985

By William C. McBee

A sulfur concrete technology has been developed by the U.S. Department of the Interior, Bureau of Mines, in which chemically modified sulfur is utilized with suitable mineral aggregates to produce construction materials which are resistant to corrosion by acids and salts. This report presents a summary of the basic technology and results of testing the materials under actual operating conditions in 50 corrosive environments in 40 commercial plants. After 4 years of testing, there was essentially no evidence of material degradation or loss of strength. Regular concrete materials were attacked and in some cases completely destroyed under the same conditions. Testing is continuing to establish ultimate longevity and durability of the sulfur concretes. The materials are finding widespread applications in metallurgical, chemical, and fertilizer processing plants.

Jan 1, 1983

By Michael Cruickshank

All life on Earth relies on the ocean and yet the ocean is 95 percent unexplored, unknown and unseen by human eyes,? said Paula Keener, director of education programs for National Oceanic and Atmospheric Administration?s (NOAA) Office of Ocean Exploration and Research. ?To better understand, manage and protect the ocean and its resources, NOAA believes it is critical to use the best technology to explore, discover, inform, educate and motivate? (MTS, newsletter, January 2011). In the last few decades, our understanding of the global mineral resource base has been drastically changed by some surprising new developments. The potential for commercial minerals per unit area in the oceans and seabed appears to be similar to that of the terrestrial lands. Thus, almost three-fourths of the global mineral resources are in, or under, the sea and are virtually undeveloped. The area of the Pacific seabeds alone is greater than the total area of the global lands. Half of the global seabed minerals are now controlled by nation states within their Exclusive Economic Zones (EEZ). The other half is controlled by the United Nations (UN) through the International Seabed Authority (ISA) within the ?areas beyond national jurisdiction? known as The Area. Thus, the Law of the Sea, ratified in 1994, has resulted in the largest transfer of control of natural resources in the history of mankind. This paper was prepared by the Society for Mining, Metallurgy and Exploration (SME) Committee on the Offshore Technology Conference for the SME Board of Directors and other interested parties. As the premier professional society for the mining and mineral community in the United States, with a history dating back to the 19th century, SME?s mission is to encourage and support young men and women engineers in the minerals industry, provide the services they need, improve the image of the industry, strengthen the networking among global industry professionals and engage in proactive collaboration among industry, government, academia and nongovernmental organizations (NGOs). The accomplishment of this mission can be strongly advanced by highlighting what is probably now the most significant development in the history of the modern minerals industry - the exploration of the marine environment and the understanding of the potential for the development of the minerals therein.

Jan 1, 2011

By D. Arku

The increased use of sensors to facilitate automation has led to an explosion of data. As data sets grow in size, their use becomes more complex. Therefore, there is an incentive for reducing the size of the datasets, as long as this does not compromise information gleaning. With this in mind, this project explored basic aggregation as a viable alternative to amassing large amounts of data. The goal of the project was to determine if one would arrive at different conclusions had they analyzed aggregated data instead of raw data. In a mine, operational data is typically used for tracking process statistics, correlation between factors, autocorrelation and multivariate models (for a factor of choice). Therefore, this project compared results from such analyses when it was conducted with aggregated data (AD) with the results of analyses conducted with raw data (RD). The data consisted of one-minute-apart readings from a semiautogenous grinding (SAG) mill on the horsepower, feed rate (tons per hour), rotations per minute (rpm), noise, recycle (tons per hour), density (% solids) and bearing pressure (psig). This data was aggregated by averaging five and 10 continuous (one-minute) observations. Changes in statistical measures between the two approaches were typically within 5% of each other. Differences in correlation coefficients between RD and AD(s) were also within this range. Autocorrelations present within RD were preserved in AD, as long as the time lags were scaled for the amount of aggregation. Regression and neural network models were also developed for power consumption. The prediction performance of developed models was similar whether one used raw data or aggregated data. Overall, it appeared that aggregating the data based on 5- or 10-minute time spans would not have resulted in conclusions (from simple or complex analyses) being different from using raw data. In other words, whether one had used raw data or aggregated data, the conclusions would have been the same, suggesting that time domain aggregation, a common industry practice, is a good alternative to storing high-density data in this case.

The 32nd annual American Hall of Fame Awards Banquet and Fundraiser, sponsored by the Mining Foundation of the Southwest (MFSW), will be held at the JW Marriott Tucson Starr Pass Resort & Spa on Saturday, Dec. 6, 2014. Each year, one living Hall of Fame inductee, up to three Medal of Merit recipients, honorees from mining?s past, and recipients of an Industry Partnership Award and a Special Citation are recognized for their respective contributions to the mining industry. Armine Frederick Ban?eld Jr., past chairman and founder of Mintec, Inc. located in Tucson, AZ, will be honored as the 2014 Hall of Fame Inductee at the awards banquet. Banfield founded Mintec from his Tucson apartment in 1970 and expanded it to a global operation. Under his guidance, Mintec won the 2013 President?s E-Award for Exports ? the highest recognition any United States company may receive for making a significant contribution to the expansion of U.S. exports. Medals of Merit will be awarded to Corale L. and James A. Brierley, founder and principal of Brierley Consultancy LLC; David Nicholas of Call and Nicholas Inc. and Scott M. Shields of Joy Global. The Brierleys are being recognized for their true scientific partnership with parallel achievements in academia and in business development. Nicholas is being recognized as the co-founder of Call & Nicholas and for his noted expertise in mining geotechnical engineering. Shields is being recognized for his innovative work with GPS integration and for playing a key role in laying the foundation for autonomous mines of the future. As representatives of mining heritage, the Hall of Fame will induct Patrick E. Connor, ?Father of Utah Mining,? for pioneering mineral exploration efforts in Utah; Earl Tappan Stannard, president of Kennecott Copper Co., for transforming Kennecott in to one of the largest U.S. copper producers; Arthur Barrette Parsons, mining editor and author, for his book ?The Porphyry Coppers in 1933,? a seminal work detailing the history and technical information regarding major porphyry copper deposits and Ernest R. Dickie, general manager of Bagdad Copper Co., for his foresight in converting the mine from block caving to open pit. The Industry Partnership Award will be presented to Empire Southwest, a third generation family owned dealership for Caterpillar which consistently ranks among the top Caterpillar dealers worldwide. A Special Citation will be presented to employees of Rio-Tinto-Kennecott Bingham Canyon Mine for their speedy recovery from the massive Manefay slope failure in 2013.Early sponsors include Ames Construction, Asarco LLC; Brierley Consultancy LLC; Caterpillar Inc.; Click Automotive Team; Deconcini McDonald Yetwin & Lacy, P.C.; Empire Southwest; Florence Copper Inc.; Freeport-McMoRan Copper & Gold Inc; Independent Mining Consultants Inc.; Joy Global Inc.; Komatsu America Corp.; Liebherr Mining Equipment; Lowell Copper Ltd.; M3 Engineering & Technology; Modular Mining Systems Inc.; MWH Global; Newmont Mining Corp.; Ram Enterprise; Rio Tinto/Kennecott, Sonoran Process Equipment Co.; Southwest Energy LLC and SRK Consulting. MFSW is a nonprofit organization and its mission to promote the value of the industry to our community and profession to ensure its future success. Funds raised from its annual banquet are principally designated to support the foundation?s education program, a partnership with the Lowell Institute for Mineral Research at the University of Arizona.

By Richard Giffen, Michael Trabold, Pablo Lemus

"As part of the new 2nd Ave Subway Project, an existing tunnel constructed in the 1970’s will be connected to the new subway and used as new running tunnels. The existing tunnel had to be modified to comply with newer structural and fire life safety codes and to be connected to the new cut and cover station at 96th St. This paper will discuss the complexities of tying an existing tunnel constructed over 40 years ago into the new station and allowing for movements due to the unloading of the existing tunnel and the differential settlement of the two structures during both the construction and permanent condition. Topics that will be discussed include structural analysis, ground improvement techniques, selection of support of excavation walls, working in contaminated soil and instrumentation and monitoring of the structures. It will also cover retrofitting the tunnel to comply with updated Fire/Life/Safety requirements. PROJECT OVERVIEW The Second Avenue Subway (SAS) will be the first major expansion of New York’s subway system in over 50 years. To be constructed in four phases, it will run from 125th St. in Harlem to Hanover Square in the Financial District (see Figure 1). For most of its length, the alignment is directly under the Second Avenue roadway."

Jan 1, 2016

By Rui Xiang Yang, Cong Li, Jia Zeng, Rong Liang Zhang, Wei Zhang, Chao Fan Tang

This research took the roasted products obtained by leaching copper (Cu) refining slag using waste acids and roasting leaching residues with calcium oxide (CaO) as raw materials and used oxidative leaching to extract Cu from roasted products using waste acids. Influences of the leaching temperature, liquid–solid ratio, and sulfuric acid ( H2SO4) concentration in waste acids on the leaching rate of Cu in the oxidative leaching process of roasted products using waste acids were investigated. The unreacted-core shrinking model of heterogeneous reactions was adopted to reveal the leaching kinetics of Cu in the oxidative leaching process of roasted products using waste acids. Results show that the leaching rate of Cu reaches 91.68% when the leaching temperature, liquid–solid ratio, H2SO4 concentration in waste acids, and injected airflow are 80 ℃, 8:1, 1.5 mol/L, and 200 mL/min, respectively. If the leaching temperature is below 80 ℃, the leaching process of Cu is controlled by the solid-film diffusion, and the apparent activation energy Ea is 11.0835 kJ/mol; at a leaching temperature above 80 ℃, the leaching process of Cu is governed by the interfacial chemical reaction, with an apparent activation energy Ea of 42.3183 kJ/mol. The liquid–solid ratio can positively influence the reaction rate constant. The apparent order of the leaching reaction of Cu is 0.632.

Jan 11, 2023

The 31st annual American Hall of Fame Awards Banquet and Fundraiser sponsored by the Mining Foundation of the Southwest (MFSW) will be held at the JW Marriott Tucson Starr Pass Resort on Saturday, Dec. 7, 2013. Each year, one living inductee, two Medal of Merit recipients, honorees from mining?s past, an industry partnership award, as well as a special citation, are recognized by the MFSW for their respective contributions to the mining industry. James D. Toole, past president and chief executive officer of Southwest Energy LLC, will be the Hall of Fame inductee, guest of honor, and featured speaker at the awards banquet. Toole founded Southwest Energy LLC in 1973 and is credited with introducing innovative explosive technology, providing even greater value to its mining customers. Medals of Merit will be awarded to Joseph M. Keane, principal metallurgical engineer for SGS Metcon Research/KD Engineering, and Sean D. Dessureault, associate professor at the University of Arizona. Keane is recognized for his metallurgical expertise, especially in design development and pollution abatement. Dessureault is recognized for his advanced mining research, with more than 25 journal publications, and his entrepreneurship as the founder and chief executive officer of two mineral-related companies. To honor mining?s past, the hall of fame will induct Bartolomé de Medina for his invention of the patio process for recovering silver; Ben Williams for his management of the Copper Queen Mine in Bisbee, AZ; Charles E. Mills for his contributions at Morenci and Inspiration Copper and founding Apache Powder Co. and The Valley National Bank; John S. Finlay and Edwin B. Royle for their invention of the mucking machine; and Louis Caryl Graton for his ore deposits research and teaching economic geology at Harvard University.

Nov 1, 2013

By Thomas F. Clemens

This paper covers various changes in government regulations, taxation, and legislation for the past two plus years and the up- coming one. Part of the paper will discuss recent business conditions and how they have affected the cement and lime industry.

Jan 1, 1983

By TOMI GIORGIO DE, Ricardo Tichauer

Mineral exploration is a key factor for success in the mining industry. However, exploration best practices are often ignored in small-scale mining. This works presents the Tichauer-DeTomi Matrix, a methodology that measures the level of compliance of exploration programs in small-scale mining with the industry best practices. The matrix has been applied to three projects in Brazil: an artisanal gold mine in the state of Pará, a small-scale manganese project in the state of Bahia, and a small-scale manganese project in the state of São Paulo. The application of the matrix resulted in indexes that represent the level of maturity of the exploration program in each project and indicate priority actions for reduction of the geological uncertainty. Therefore, the Tichauer-DeTomi Matrix has shown potential to be a useful tool for assessment of geological uncertainty in small-scale mining. As a risk indicator, it may contribute to promoting investment in small-scale mining and development for communities that depend on this activity around the world.

By Roger Storry, Arnaud Hochart, David Harris, Olivier Martin

"INTRODUCTIONThe Port of Miami Tunnel (POMT), designed and constructed by Bouygues Civil Works Florida between 2009 and 2014, was a Public Private Partnership between the Miami Access Tunnel Concessionaire, Florida Department of Transport, Miami-Dade County and the City of Miami. The project comprises dual 11.3m internal diameter, 1.27km long, twin lane road tunnels running between Watson and Dodge islands under the main shipping channel in Biscayne Bay. Five cross passages (CPs), spaced at 200m centre to centre, provide emergency access between the two tunnels, as shown in Figure 1.The CPs were constructed by open-face excavation methods but the particular geological conditions at the project site (loose and variable carbonate sedimentary strata with very high permeability) required specific ground treatment solutions to provide safe excavation conditions and to ensure the long term serviceability of the permanent works construction. Where access allowed, ground treatment was performed from the ground surface using deep-mixing techniques; however, at two locations (CP2 and CP3) surface access was restricted and ground treatment by freezing, performed from the tunnels, was required. The CPs are 12.3m long with an excavation diameter of 5.8m and are located up to 30m below the water table partly or wholly within the Key Largo limestone (termed Layer S7 in the ground model). Layer S7 is a coralline limestone having a metastable honeycomb structure and high variable porosity. At CP2 the upper portion of the excavation was within the overlying Anastasia Formation limestone (Layer S6), comprising a highly permeable coquina. The geological profile along the project is shown in Figure 2.This paper presents aspects of the freeze design and the risk mitigation necessary to successfully achieve the construction of the CPs in the unique geological conditions."

Jan 1, 2016

By VÍCTOR VÁZQUEZ-VÁZQUEZ, GUILLERMO TIBURCIO-MUNIVE, María M. Salazar-Campoy, JESÚS L. VALENZUELA-GARCÍA, OFELIA HERNÁNDEZ-NEGRETE

This study examines a process for the recovery of precious metals from difficult minerals that exhibit refractory characteristics to cyanidation: low extraction of metals and high consumption of leaching reagent. A mineral sample from Monte del Favor Mine, located in Hostotipaquillo, Jalisco, Mexico, was physically and chemically characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fire assay and atomic absorption spectroscopy (AAS). Two stages of leaching were carried out, first to eliminate manganese from the sample using sodium sulfite (Na2SO3) as a reductive reagent along with sulfuric acid (H2SO4), and second to dissolve gold and silver with hydrochloric acid (HCl) and sodium hypochlorite (NaClO). The results show extractions of around 96 percent for manganese (Mn), 98.73 percent for silver (Ag) and 83 percent for gold (Au). The usefulness of high acidity and Na2SO3 to obtain better results in Mn and Ag leaching are discussed along with the roles that HCl and NaClO play in Ag and Au dissolution values.

By Bryan Ulrich

On March 20, 2014, the ?Roundtable Discussion on Innovations in Heap Leaching and Mine Waste Management? was hosted by Knight Piésold and Co. at the Red Lion Hotel in Elko, NV. This topic is timely, and formed something of a lead into the inaugural ?Workshop on Innovations in Waste Rock, Tails and Heap Leach Management.? That workshop, which grew from the 2013 Elko Roundtable, was held on the University of Nevada, Reno (UNR) campus on May 19, 2014. The workshop was hosted by UNR and the University of British Columbia. Knight Piésold?s local representatives, Bryan Ulrich and Logan Jensen, were joined by Tom Kerr, president of Knight Piésold?s, U.S. practice; Rick Frechette, senior vice president, environmental services and Jeff Coffin, geotechnical engineer, from the Denver, CO office for the roundtable event. The event played host to about two dozen attendees from several western states.

By R. J. Caine

Like most major firms engaged in project management, Dravo Corporation faces a constant challenge to keep its management systems in tune with the ever-increasing demands imposed by larger and more complex projects. This paper suggests that one of the key elements in meeting this challenge is more effective organization of project data. It reveals some of the details of a program at Dravo's Minerals 6 Metals Division which seeks, through better organization of project data, to improve Dravo's capabilities in estimating, cost control, scheduling, performance reporting and material control. In particular, this paper discusses ideas Dravo is developing for improved job numbering, codes of accounts, requisition and purchase order numbering, inventory cataloging, and employee/badge numbering.

Jan 1, 1980

By Danny Chan, Shahram Tafazoli, Nicholas Himmelman, Edmond Chow

"While wearable technology has been garnering attention in the consumer market, enterprise and industry have just begun exploring its potential applications. Since February 2014, Motion Metrics International has been working in collaboration with Vandrico Solutions Inc. to apply wearable technology to improve productivity and safety in the mining industry.This article discusses the value proposition of using wearable technology to deliver critical notifications in mining. The advantages and disadvantages of various form factors are explored. The challenges, both specific to mining and in general to wearable technology, are defined. Finally, the concept of MetricsGear, the first wearable technology platform developed for mining by Motion Metrics International in collaboration with Vandrico Solutions Inc., is described. MetricsGear is designed to notify the user with minimal distraction to keep the user focused on his or her primary task and aware of mission-critical events. This focus and awareness allows the user to work more efficiently and safely. The mining process consists of a series of intricate stages, where certain events or conditions in one stage can have a huge impact on other stages. The notification of these critical events or conditions is vital for ensuring the overall efficiency of the mining process. Critical notifications can be classified as two types: timecritical events and contextual information. Time-critical events are situations where a timely response from a responder can have a significant impact on seizing an opportunity or mitigating cost. Some human-computer interaction (HCI) experts classify notification types based on the interruption, reaction and comprehension (IRC) framework. Time-critical events are classified to have high interruption, high reaction and low comprehension due to their urgency. The responder should have just enough information to identify the crisis and react as soon as possible (Chow, 2014). For example, when a tooth is lost during shovel operation, it is necessary to recover the missing tooth before it jams the primary crusher. The consequence of missing this critical time period is a jammed crusher that can cause the mine to be out of production until the jammed tooth is extracted (Baumann, 2013). In this case, the responder only needs to see an image to confirm if the tooth is missing and information to identify which equipment and when the tooth went missing (Fig. 1)."

Jan 1, 2014