Mining industry and business excellence

Mining has been incorporated to mankind activities since the earliest times.  During the Stone Age, humans fashioned tools from a variety of rocks, including flint, chert, basalt and sandstone. These materials were initially collected as loose rocks and, as demand grew, open pit and underground mining methods were developed. Initially, early humans were motivated to mine for survival. They focused their efforts on manufacturing utilitarian objects such as tools, hunting implements and storage vessels. Eventually, as they became more skilled at survival, they turned their attention to using earth materials for uniquely human endeavors, such as adornment, art, spiritual practices and ritual. The Stone Age eventually gave way to the Bronze Age when early man discovered the technique of smelting (Adapted from Kogel, 2013). Silver mines in Laurion (Greece) and Rio Tinto (Spain) are well known examples of ancient mining sites.

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Figure 1: Stone tools have been used by humans for at least two million years

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Figure 2: Famous Carrara marble in Italy

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Mining is closely associated with our daily lives as well as our economy. Rock and minerals (e.g. bauxite, iron, copper, limestone, phosphate, lithium, uranium and gold) are used in industries such as electronics, power generation, construction, farming, healthcare, metallurgy, among many others. According to the U.S. Geological Survey, about 40,000 pounds of minerals and energy are needed each year for every American. In 2014, the total value of world exports of mining products reported by the World Trade Organization was $ 3,789 billion.

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Figure 3: Mineral, metal and fuel consumption

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Mining can be defined as the activity, occupation, or industry involved with mineral extraction. Mining is preceded by geological investigations to locate the deposit, economic analyses that prove it is financially feasible and following by development and actual extraction of minerals, including required preparation, beneficiation and marketing. Also, once the deposit is depleted, reclamation and closure of the mine site complete the mining enterprise. In some cases, reclamation can be carried out as extraction is taking place: progressive reclamation (Adapted from Miller et al., 2010).

Typically modern mining operations are characterized by five specific stages: prospecting, exploration, development, exploitation, reclamation and closure.

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Figure 4: Mine Cycle

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The mining industry is known for conservative thinking and reluctance to change – the desire to be “first to be second” is a common refrain when it comes to implementing new technology. And yet this is not entirely true. Creative financial deals, new ways to focus on safety and, in some cases, new approaches to community engagement, health and wellness are fine examples of innovation. Furthermore, considerable risks are taken with exploration in remote and challenging places, and some of the best acquisitions are made when market conditions appear negative. The industry is willing to be adventurous and has the ability, albeit not always evident, to protect against downside risks (Adapted from Thompson, 2015).

An interesting aspect of the mining industry is “the general improvement paradox”. When times are good, it is often not possible to justify technological improvements to an operating process because the down time cannot be paid for by the incremental benefit. Unfortunately, when times are bad, the business cannot justify the increased capital investment that it needs to run at lower costs and higher efficiency (Adapted from Shook, 2015).

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Business excellence is about developing and strengthening the management systems and processes of an organization to reach its full potential. It requires achieving excellence in everything that an organization does (including leadership, strategy, customer focus, information management, people and processes) and most importantly achieving superior business results. (Adapted from Mann et. al, 2012).

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Lastly, I would like to re-enforce the concept of creativity and its important association with practicality. Creative solutions must consider nuts and bolts, be economically feasible and add value to stakeholders.

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Figure 5: Customized truck unloading stemming stones for blasting

References:

 

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Platinum Group Metals (PGMs)

Platinum Group Metals (PGMs)

Overview

The platinum group metals consist of six elements that are characterized by similarity, namely platinum, iridium, osmium, rhodium, ruthenium and palladium. Based on their densities, the first three are categorized as heavy, while the last three are regarded as light. PGMs are superb catalysts in addition to other characteristics like corrosion resistance, high melting points and chemical stability. It is precisely these characteristics that make PGMs highly desirable in many applications. Currently, the single largest market for the three most important PGMs (i.e. platinum palladium and rhodium) is the automotive sector, specifically the catalytic converter industry. PGM resources are rare and 80% of the world’s platinum reserves are located in South Africa (Adapted from Department of Research and Information, 2013).

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Figure 1: Two Rivers Mine In South Africa

Applications

The leading demand for PGMs continued to be catalytic converters to decrease harmful emissions from automobiles. PGMs are also used in the glass industry; in jewelry; in the chemical industry for catalysts in nitric acid and other bulk-chemical production, for refining petroleum, and for fabricating laboratory equipment; and in the electronics industry in computer hard disks to increase storage capacity, in multilayer ceramic capacitors, and in hybridized integrated circuits. Platinum and palladium, along with gold-silver-copper-zinc alloys, are used as dental restorative materials. Platinum, palladium, and rhodium are used as investment in the form of exchange-traded products, as well as physical bars and coins (Adapted from US Geological Survey, 2015). According to Department of Research and Information (2013), PGMs demand are distributed as following: autocatalysts (39%) and industrial applications (22%), Jewelry 31% and investment demand (8%), particularly through exchange traded funds (ETFs).

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Figure 2: Downstream applications of PGM

Geology and Key Producing Regions

There are broadly considered to be four main types of economic PGM mineral deposits (Adapted from Mudd and Glaister, 2009 and Vermaak, 1995):

  • Norite intrusions: Where meteoritic impact has been instrumental in PGM emplacement; eg. Sudbury Irruptive Complex in Ontario, Canada (~10-1000 Mt, 1-3 g/t, ~2-3% Ni+Cu);
  • Stratiform deposits: Where PGMs occur in large Pre-Cambrian mafic to ultramafic layered intrusions, such as the Merensky and Upper Group 2 Chromitite (UG2) Reefs of the Bushveld Complex in South Africa, Great Dyke in Zimbabwe and the Stillwater complex in Montana, United States (usually ~10-1000 Mt, grade 3-10 g/t PGMs, ~0.2-1% Ni+Cu);
  • Ni-Cu bearing sills: Related to rift structures and concordant intrusive sheets, eg. Noril’sk-Talnakh District, Russia, and Jinchuan deposits, China (~10-1000 Mt, 5-10 g/t, ~3-5% Ni+Cu);
  • Placer deposits: Alluvial deposits containing coarse PGMs (mainly Pt) were mined with alluvial gold for ~2,000 years prior to the 20th century . Columbia produced 1.4 t alluvial Pt in 2007;

However, most of the primary PGM’s come from low-sulfide platinum ores (South Africa and the U.S.A) and from sulfide copper-nickel ores (Russian and Canadian deposits).

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Figure 3: Sperrylite (Silver-colored) in platinum-copper ore

World resources of PGMs are estimated to total more than 100 million kilograms. The largest reserves are in the Bushveld Complex in South Africa. South Africa has over 80% of global PGM reserves, with Zimbabwe holding a further 7% and Russia 8%, with the three countries claiming 95% of global reserves.

World mine production of PGMs was 393,000 kg in 2014 (decreasing by about 14% from 455,000 kg in 2013). South Africa accounted for 48% of total PGM mine production in 2014; Russia, 30%; Canada, 7%; Zimbabwe, 7%; the United States, 4%; and other countries, 3%. In 2014, world platinum mine production decreased by 21%. In South Africa, which accounted for 64% of world platinum production, production totaled 94,000 kg of platinum, a 28% decrease from that in 2013, accounting for most of the decrease in global production. Global mine production of palladium in 2014 decreased by 5% to 193,000 kg, with Russia and South Africa accounting for 43% and 30%, respectively, of production; Canada and the United States accounting for 10% and 6%, respectively; and Zimbabwe accounting for 5%. World mine production of other PGM s (iridium, osmium, rhodium, and ruthenium) decreased by 21% in 2014 compared with that of 2013. South Africa, which accounted for 71% of global production, accounted for most of the decrease of other PGMs. Estimated production in Russia, the second leading producer, remained unchanged (Adapted from US Geological Survey, 2016).

Mining and Processing

The mining of PGM ores is through conventional underground or open cut mines. The next stage is grinding and gravity-based (or dense media) separation, followed by flotation to produce a PGM-rich concentrate. The concentrate is then smelted to produce a PGM-rich Ni-Cu matte, with the PGMs extracted and purified at a precious metals refinery. The processing is therefore more analogous to base metals rather than Au-Ag mills which use cyanide-based hydrometallurgy. Smelting of Ni-Cu concentrates can also be a modest source of PGMs (eg. Russia, Canada). (Adapted from Mudd and Glaister, 2009).

Most of the PGM mines in South Africa operate at a depth below 500 meters and up to 2 kilometers. Their orebodies are tabular and narrow, varying in width between 0.9 meters and 2.1 meters and requiring labor-intensive mining techniques. PGM ore is drilled and broken with explosives before being removed through mechanical transportation methods to the surface; electricity consumption is high, not only for ore haulage but also to drive compressed air to the miners’ hand-held pneumatic drills and, because the hard rock in platinum mines has a high thermal gradient, to refrigerate the working areas. On the surface the ore is crushed and milled into fine particles. Wet chemical treatment known as froth flotation produces a concentrate which is dried and smelted in an electric furnace at temperatures over 1,500°C. A matte containing the valuable metals is transferred to converters to remove iron and sulfur. PGMs are then separated from the base metals nickel, copper and cobalt, and refined to a high level of purity using a combination of solvent extraction, distillation and ion-exchange techniques (Adapted from IPA, 2013).

Process

Figure 4: Generic flow chart for PGM production in South Africa

 

Key Issues (Adapted from Vronsky, 1997)

The annual supply of platinum is only about 130 tons – which is equivalent to only 6% (by weight) of the total Western World’s annual mine production of gold. All the platinum ever mined throughout history would fill a basement of less than 25 cubic feet.

Approximately, 10 tons of ore must be mined – sometimes almost a mile underground at temperatures greater than 120 degrees Fahrenheit – to produce one pure ounce of the “so-called white gold.” Furthermore, the total extraction process takes six long months. Also, production is concentrated in very few sites around the world.

Unlike gold, there are no large inventories of above-ground platinum. Therefore, any breakdown in the two major supply sources would catapult the price of platinum into orbit.

Market

The performance of the automobile industry will have the greatest impact on future consumption of these PGM s. Global automobile production is expected to increase, particularly in emerging markets, such as China and India, as well as in developed markets in the United States and Europe. In the electronics industry, palladium demand is expected to increase owing to increased demand for electronic items, such as tablets and other mobile devices, as well as a continued demand for laptop and desktop computers. The demand for platinum in the jewelry industry is expected to increase, especially in China, owing to lower prices (U.S. Geological Survey, 2016).

According to The World Platinum Investment Council (Platinum Quarterly), Global platinum demand is projected to increase to 8,255 koz during the full year 2016 – up from 8,220 koz in 2015. Growth is being powered by strong investment demand, forecast to rise to 350 koz in 2016; assisted by booming demand in Japan. Jewellery consumption is expected to increase by 1% during the full year, with growth in India, the US and Europe offsetting weaker demand elsewhere. Automotive demand is forecast to remain largely similar to 2015, down only 1% from the previous year. On the supply side the estimate of the amount of total mining supply and recycling for the full year has been reduced by 230 koz. Total supply is forecast to decrease by 1% to 7,800 koz this year, lower than the pre-strike level of 2013, as lower refined production from South Africa and Russia outweighs increases in other regions and from recycling. Refined supply is forecast to be 5,895 koz in 2016, with total mining supply at 5,995 koz with some sales from producer inventory expected. Platinum recovered via recycling is estimated to increase by 95 koz (+6%) to 1,805 koz, with secondary supply from autocatalysts growing to 1,305 koz (+10%), rebounding as volumes recover alongside the improvement in metal prices.

This month (July, 2016) palladium is up 16 per cent to $697.92 a troy ounce, while platinum has risen 11 per cent to $1,138 a troy ounce (Sanderson, 2016).

Have you been inside a deep underground platinum mine? See the video below for some insights.

Underground Platinum Mine

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Department of Research and Information “Industry analysis: Opportunities for downstream value addition in the platinum group metals value chain: Fuel cells”, Industrial Development Corporation of South Africa Limited. (February 2013). Last accessed on 07/31/2016 at http://idc.co.za/images/2015/PGMsMetalsValueChain.pdf

C.F. Vermaak, “The Platinum-Group Metals – A Global Perspective”, Mintek, Randburg, South Africa, 247p, 1995.

Mudd, G M and Glaister, B J, “The Environmental Costs of Platinum-PGM Mining: An Excellent Case Study In Sustainable Mining. Proc.“ 48th Annual Conference of Metallurgists”, Canadian Metallurgical Society, Sudbury, Ontario, Canada, August 2009.

U.S. Geological Survey, “2014 Mineral Commodity Summaries”. U.S. Department of the Interior. (January, 2015). Last accessed on 07/31/2016 at http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2015-plati.pdf

U.S. Geological Survey “2014 Minerals Yearbook”. U.S. Department of the Interior. (January, 2016). Last accessed on 07/31/2016 at http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2014-plati.pdf

International Platinum Group Metals Association (IPA) “The Primary Production of Platinum Group Metals (PGMs)”. International Platinum Group Metals Association, Munich – Germany. (2013). Last accessed on 07/31/2016 at http://ipa-news.com/assets/sustainability/Primary%20Production%20Fact%20Sheet_LR.pdf

Vronsky, I. M, “Platinum: The Rich Man’s Gold”, Gold-Eagle Website, May 1, 1997. Last accessed on 07/31/2016 at http://www.gold-eagle.com/article/platinum-rich-mans-gold

Sanderson, H, “Platinum, palladium chase down gold’s stellar showing”, Financial Times, Commodities, Website, July 2016, 2016. Last accessed on 07/31/2016 at http://www.ft.com/cms/s/0/79c5652a-54b8-11e6-befd-2fc0c26b3c60.html#axzz4G0WwDatq

Photos Credit:

Feature: An assortment of nuggets of native platinum. Author: Aram Dulyan

Figure 1: Two Rivers mine in South Africa. Author: Ryanj93

Figure 2: Downstream applications of PGMs. Author: Platinum Beneficiation Committee

Figure 3: Sperrylite (silver-colored) in platinum-copper ore. Author: James St. John.

Figure 4: Generic flow chart for PGM production in South Africa. Author: Lonmin

Iron Ore

Iron Ore

Overview

Iron (Fe) is one of the most abundant rock-forming elements, constituting about 5% of the Earth’s crust. It is the fourth most abundant element after oxygen, silicon and aluminum and, after aluminum, the most abundant and widely distributed metal. Iron is indispensable to modern civilization and people have been skilled in its use for more than 3,000 years. However, its use only became widespread in the 14th century, when smelting furnaces (the forerunner of blast furnaces) began to replace forges. Iron ores are rocks from which metallic iron can be economically extracted. These rocks are usually found in the form of hematite (Fe2O3) or magnetite (Fe3O4). About 98% of world iron ore production is used to make iron in the form of steel (Adapted from Geoscience Australia, 2011).

Mining iron ore is a high volume and low margin business since the value of iron is significantly lower than other base metals. It is highly capital intensive, and requires investments in mining facilities as well as in infrastructure such as railways and harbor to facilitate the transport of iron ore (Adapted from Ou, 2012).

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Figure 1: Massif Hematita – Iron Ore

Applications

Although iron in cast form has many specific uses (e.g. pipes, fittings, engine blocks) its main use is to make steel. Steel is the most useful metal known being used 20 times more than all other metals put together. Steel is strong, durable and extremely versatile. The many different kinds of steel consist almost entirely of iron with the addition of small amounts of carbon (usually less than 1%) and of other metals to form different alloys (e.g. stainless steel). Pure iron is quite soft, but adding a small amount of carbon makes it significantly harder and stronger. Most of the additional elements in steel are added deliberately in the steelmaking process (e.g. chromium, manganese, nickel, molybdenum). By changing the proportions of these additional elements, it is possible to make steels suitable for a great variety of uses (Adapted from Geoscience Australia, 2011).

Steel’s desirable properties and its relatively low cost make it the main structural metal in engineering and building projects, accounting for about 90% of all metal used each year. About 60% of iron and steel products are used in transportation and construction, 20% in machinery manufacture, and most of the remainder in cans and containers, in the oil and gas industries, and in various appliances and other equipment (Adapted from Geoscience Australia, 2011).

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Figure 2: Stockpile of coal and iron ore, Detroit Michigan

Geology and Key Producing Regions

Although iron is present in most common rock types, it is generally uneconomic, or in forms that are not readily processed. Iron-ore deposits generally have >25 wt % Fe, usually in the form of hematite (Fe2O3), magnetite (Fe3O4), goethite (FeO(OH)), limonite (FeO(OH)•nH2O) or siderite (FeCO3). Iron-ore deposits are found in a wide range of igneous, sedimentary and metamorphic rocks. Examples of igneous iron ores include magnetite accumulations in mafic intrusions, as well as large deposits of probable magmatic–hydrothermal affinity, such as Kiruna in Sweden. However, most (>90%) of global iron-ore production comes from iron-rich cherty sedimentary rocks and their metamorphic or supergene derivatives, grouped under the general term ‘iron formations’. Iron formations are stratigraphic units of bedded or laminated sedimentary rocks or layered metasedimentary rocks with >15% Fe. They can be subdivided into two main types, based on their tectonic settings, associated rocks, and depositional environment. Algoma-type iron formations are associated with submarine-emplaced volcanic rocks, especially in greenstone belts. Lake Superior type iron formations formed on continental-margins, without direct relationships with volcanic rocks, and are typically much larger than Algoma-type iron formations. Lake Superior-type iron formations are most common in Precambrian sedimentary successions, with peaks in iron sedimentation between ~2.65 and 2.32 billion years ago (Ga) and again from ~1.90 to 1.85 Ga (Adapted from Conliffe, Kerr and Hanchar, 2012).

Iron ore is mined in about 50 countries. China was the leading global producer of iron ore, accounting for 47% of iron ore production by gross weight (29% by metal content), followed by Australia, Brazil, and India.  Australia and Brazil together dominate the world’s iron ore exports, each having about one-third of total exports (U.S. Geological Survey, 2016).

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Figure 3: Mount Whaleback Mine, Australia

Mining and Processing (Adapted from U.S. EPA, 1994).

Iron ore is almost exclusively mined by surface operations. The most predominant surface mining methods used for mining of iron ores are open pit mining methods and open cut mining methods. Overburden and stripping ratios are important in determining whether a deposit will be mined. The stripping ratio describes the unit of overburden that must be removed for each unit of crude ore mined. These ratios may be as high as 7:1 (for high-grade wash ores) or as low as 0.5:1 (for low-grade taconite ores).

However a few underground iron ore mines are also in operation around the globe (e.g. caving and s Stripping ratios increase with the quality of the ore being mined and cost factors related to beneficiation and transportation.

Most beneficiation operations will result in the production of three materials: a concentrate; a middling or very low-grade concentrate, which is either reprocessed (in modern plants) or stockpiled; and a tailing (waste), which is discarded.

Primary Milling operations are designed to produce uniform size particles by crushing, grinding, and wet or dry classification. Secondary milling (comminution) further reduces particle size and prepares the ore for beneficiation processes that require finely ground ore feed.

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Figure 4: Carajas Mine, Brazil

Beneficiation processes includes:

  • Magnetic separation is most commonly used to separate natural magnetic iron ore (magnetite) from a variety of less-magnetic or nonmagnetic material;
  • Flotation is a technique where particles of one mineral or group of minerals are made to adhere preferentially to air bubbles in the presence of a chemical reagent. This is achieved by using chemical reagents that preferentially react with the desired mineral;
  • Gravity concentration is used to suspend and transport lighter gangue (nonmetallic or non-valuable rock) away from the heavier valuable mineral. This separation process is based primarily on differences in the specific gravities of the materials and the size of the particles being separated;
  • Agglomeration is used to combine the resulting fine particles into durable clusters. The iron concentrate is balled in drums and heated to create hardened agglomerate. Agglomerates may be in the form of pellets, sinter, briquettes, or nodules;

Large scale iron ore smelting are used for producing pig iron. In this process ore is put into a blast furnace along with limestone and coke and subjected to hot air blasting and heat which converts the ore to molten iron. This is tapped from the bottom of the furnace into molds known as pigs.

Key Issues

Waste materials generated as a result of open pit mining include overburden, waste rock, and mine water containing suspended solids and dissolved materials. Other waste materials may include small quantities of oil and grease spilled during extraction. Mine water contains dissolved or suspended constituents similar to those found in the ore body itself. These may include traces of aluminum, antimony, arsenic, beryllium, cadmium, chromium, copper manganese, nickel, selenium, silver, sulfur, titanium and zinc etc. (Adapted from Satyendra, 2014).

The beneficiation of iron ore typically occurs in a liquid medium. In addition, many pollution abatement devices use water to control dust emissions. At a given facility, these techniques may require between 600 and 7,000 gallons of water per ton of iron concentrate produced, depending on the specific beneficiation methods used (Adapted from U.S. EPA, 1994).

The need for the disposal of iron ore tailings in an environmentally friendly manner is of great concern (Adapted from Ghose and Sen, 2005).

Market

As a basic ingredient in the production of steel, iron ore is generally viewed as a cyclical commodity, sensitive to changes in global economic conditions. As a global commodity, the prices of iron ore typically fluctuate with changes in worldwide industrial demand. Globally, price reductions continued for seaborne iron ore in 2015 as steel production in China decreased and projects to increase iron ore production capacity continued, primarily in Australia and Brazil. Production, by gross weight, in Australia and Brazil increased by 112 million tons in 2013 and by 116 million tons in 2014, and was estimated to increase by 67 million tons in 2015. Global steel demand was forecast to decrease by 1.7% in 2015, following an increase of 0.7% in 2014. The monthly mean price of iron ore fines at 62% iron content at Tianjin Port, cost and freight, fell from the 5-year high of $187.18 in February 2011 to $56.43 in September 2015, the most recent date for which prices were available. As a result of lower prices, an estimated 200 million tons of iron ore capacity was idled between 2014 and 2015, most notably in Australia, Brazil, Canada, China, Sweden, the United States, and western Africa. Additional capacity was expected to be brought online during the next 5 years, with the largest capacity increases among the top four miners to reach 40 million tons in 2016 and 60 million tons in 2017 (U.S. Geological Survey, 2016).

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Figure 5: Iron ore train in Pilbara region, Australia

Recently, “Goldman has lifted its three-month target to $US 50 a tonne from $US 45 a tonne previously, saying port stockpiles remain at historically low levels. The bank also lifted its six-month target to $US 40, from $US 35”. Have we reached the bottom of the cycle?

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Geoscience Australia “Australian Atlas of Minerals Resources, Mines and Processing Centres”, Australian Government, Commonwealth of Australia (2011). Last accessed on 07/29/2016 at http://www.australianminesatlas.gov.au/education/fact_sheets/iron.html

Ou, L. “China’s Influence on the World’s Iron Ore Market  – A Supply-Side Perspective”. Undergraduate Honors Thesis, Department of Economics, University of California, Berkeley (2012).

U.S. Geological Survey, 2016. “Mineral Commodity Summaries”. U.S. Department of the Interior. (January, 2016). Last accessed on 07/29/2016 at http://minerals.usgs.gov/minerals/pubs/commodity/iron_ore/mcs-2016-feore.pdf

Satyendra “Mining of Iron Ores”, ISPAT Website, (March, 2014).  Last accessed on 07/29/2016 at http://ispatguru.com/mining-of-iron-ores/

U.S. EPA “Extraction and Beneficiantion of Ores and Minerals – Volume 3 – Iron”, Technical Resource Document, United States Environmental Protection Agency. Washington, DC, USA (1994).

Conliffe, J., Kerr A. and Hanchar, D. “Mineral Commodities of Newfoundland and Labrador – Iron Ore” Geological Survey Mineral Commodities Series, Number 7, Newfoundland Labrador Natural Resources, Canada. (2012).

Ghose M. and Sen, P. K. “Environmentally safe design of tailing dams for the management of iron ore tailing in Indian context”.  Journal of Environment Science and Eng. 2005 October; 47(4):296-303.

Photos Credit:

Feature: Mining Iron – Transport Conveyor Iron. Author: Sarangib

Figure 1: Massif hematite (5×7 cm). Iron ore. Author: Eurico Zimbres FGEL/UERJ

Figure 2: Hanna furnaces of the Great Lakes Steel Corporation, stock pile of coal and iron ore, Detroit, Mich. Author: Arthur S. Siegel, 1913-1978, photographer.

Figure 3: Mount Whaleback Mine Author: Graeme Churchard from Bristol, UK

Figure 4: Carajas Mine, Brazil. Author: NASA Earth Observatory

Figure 5: Iron ore train in Pilbara region, Western Australia. Author: Geez-oz

Mining and the Environment

Mining and the Environment

Mining in the early days took place at a time when environmental impacts were not as well understood and most importantly, not a matter of significant concern. During these times, primarily before the 1970s, the mining cycle did not necessarily include closure activities specifically designed to mitigate environmental or social impacts. As a result, historical mine sites may still have un-reclaimed areas, remnants of facilities, and untreated water. This inherited legacy of environmental damage from mining is not indicative of the mining cycle today. Now, mine closure and a number of activities to mitigate the social and environmental impacts of mining are an integral part of mine planning and mineral development from the discovery phase through to closure (Adapted from Hudson et. al, 1999).

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Figure 1: Dedicated camera for environmental monitoring. Author: Jim Barton

Environmental Impacts of Mining (Adapted from Aswathanaryana, 2003; Carr and Herz, 1989; and Nilsson and Randhem, 2008):

  • Lithosphere: Depending on the type of mining conducted and the site of mining there are several types of impacts on the lithosphere. The results range from formation of ridges, depressions, pits and subsidence on the surface as well as underground cavities affecting the stability of the ground. Furthermore, both the area for mining and the area used for waste dumps, occupy and degrade land that could be used for farming, agriculture or other economic activity.
  • Hydrosphere: Impacts on the hydrosphere resulting from mining include lowering of the groundwater table, mine water discharge into rivers, seas and lakes, leakage from settling tanks and evaporators that have a negative effect on the groundwater quality and pumping of water into the ground for the extraction of a mineral. Significantly lowered groundwater levels can result in significant surface depressions and drained rivers and lakes with serious impacts on surrounding agriculture for example. Furthermore, depending on the chemical composition of the rock, the drained water usually becomes highly acidic with the resulting capability of taking into solution a variety of toxic and heavy metals.
  • Atmosphere: Atmospheric emissions during mining occur not only from internal combustion engines in mining machinery but dust and gases are also released from blasts and rocks and mineral masses. One tonne of explosives produces about 40-50 m3 nitrogen oxides and huge amounts of dust. Also, smelters are commonly used for mineral purification and emissions from these processes include particulate matter and gases such as sulfur dioxide, carbon monoxide and carbon dioxide. Although some installations use different kinds of flue gas purifications, these are never completely effective.
  • Biosphere: The biosphere is adversely affected by mining mainly by pollution and by degradation of land and vegetation resulting in loss in biodiversity. Mining can also have impact on local microclimate.
  • Public Safety: Old mining sites are inherently interesting to people, but potentially dangerous as well. They may have surface pits, exposed or hidden entrances to underground workings, or old intriguing buildings. Another safety consideration at some mine sites is ground sinking or “subsidence.”

 

Key Mining Related Environmental Issues (Adapted from Environmental Law Alliance Worldwide, 2010):

  • Greenhouse Gases: Reduction in greenhouse gas emission as an initiative for minimizing the heat retention caused by the accumulation of greenhouse gases around the earth.
  • Acid Rock Drainage (ARD): When the sulfides in the rock are excavated and exposed to water and air during mining, they form sulfuric acid. This acidic water can dissolve other harmful metals in the surrounding rock. If uncontrolled, the acid mine drainage may runoff into streams or rivers or leach into groundwater.
  • Toxicity: Humans and the surrounding ecosystem can be impacted by not only the physical effects of mining, but also the toxicological impacts of minerals mined, chemicals used, and byproducts of the overall refining process.
  • Biodiversity: Biodiversity is the variation of organisms within a given species, ecosystem, and/or biome. The number of species and the variety of genetic material available within a population determines the diversity within an ecological system. Biodiversity promotes species adaptation and evolution.
  • Erosion and Sedimentation: Though erosion and sedimentation are naturally occurring processes, mining and mine-related activities amplify their effect, and may negatively affect the surrounding environment. In the absence of adequate prevention and control strategies, erosion can carry excessive amounts of sediment into streams, rivers, and other surface waters and aeolian movement can affect broader terrestrial ecosystems.
  • Water and Groundwater Supply: Large volumes of groundwater are either discharged, or are used by the mining and associated supporting operations. Also, drawing down the water table and diverting runoff to other watersheds may reduce the volume of water available for other uses (e.g., fisheries).
  • Tailings Management: Tailings are the rejected materials after the process of separating the valuable fraction from the uneconomic fraction of an ore. Tailings management is an important aspect in the design and operation of mining projects and needs to balance a variety of considerations, including potential environmental, social, economic, public health and safety impacts.
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Figure 2: Iron hydroxide precipitate from surface coal mining

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Figure 3: Bento Rodrigues dam disaster

Although mining can have significant impact on environment, as scientific and technological advances increase the understanding of the physical and chemical processes that cause undesired environmental consequences, mines and related beneficiation or smelting facilities apply this understanding to improve prevention and solve environmental problems (Adapted from Langer et. al., 2004).

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Figure 4: Snapping turtle near the St. Lawrence River

Society’s requirement for mineral resources establishes a strong link between our standard of living, the Earth, and science. By understanding key concepts of the process of mining, citizens should be prepared for the necessary discussions and decisions concerning society’s increasing need for mineral resources and the related environmental tradeoffs. Decisions about the development and use of Earth’s mineral resources affect the economic, social, and environmental fabric of societies worldwide (Adapted from Hudson et al., 1999).

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Figure 5: Reclamation process at the Seneca Yoast coal mine

What is the most important mining related environmental issue? Are there the good practices for addressing this concern?

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Hudson, T. L., Fox, F. D. and Plumlee, G. S. “Metal Mining and The Environment”. American Geological Institute, Alexandria, Virginia (1999).

Langer, W. H., Drew, L. J. and Sachs, J. S. “Aggregate and The Environment”. American Geological Institute, Alexandria, Virginia (2004).

Hatch Ltd “Environmental Analysis of the Mining Industry in Canada”, Canadian Mining Innovation Council, Canada (2013). Last accessed on 07/27/2016 at http://www.cmic-ccim.org/wp-content/uploads/2013/07/HatchScopingReport.pdf

Nilsson, J. A. and Randhem, J. “Environmental Impacts and Health Aspects in the Mining Industry, A Comparative Study of the Mining and Extraction of Uranium, Copper and Gold”, Master of Science Thesis in the Master Degree Programme Industrial Ecology, Department of Energy and Environment, Chalmers University of Technology, Sweden (2008).

Aswathanarayana, U. “Mineral resources management and the environment”, A.A. Balkema. Tokyo, Japan. ISBN 978-90-5809-545-9. (2003).

Carr, D. D. and Herz, N. “Concise Encyclopedia of Mineral Resources”. Oxford: Pergamon Press. (1989).

Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA, (August, 2002).

Environmental Law Alliance Worldwide “Guidebook for Evaluating Mining Project EIAs”, Environmental Law Alliance Worldwide. Eugene, OR 97403 U.S.A. (July, 2010) Last accessed on 07/27/2016 at https://www.earthworksaction.org/files/pubs-others/Evaluating-Mining-EIAs-ELAW.pdf

Photos Credit:

Feature: USGS hydrologist Greg Clark measures streamflow on Government Gulch Creek, a tributarty to the Coeur d’Alene River in northern Idaho. Author: U.S. Geological Survey

Figure 1: Dedicated camera for environmental monitoring. Author: Jim Barton

Figure 2: Iron hydroxide precipitate (orange) in a Missouri stream receiving acid drainage from surface coal mining. Author: D. Hardesty, USGS Columbia Environmental Research Center

Figure 3: Bento Rodrigues dam disaster Author: Brazilian Senate

Figure 4: Head-on view of a snapping turtle (Chelydra serpentina) hidden near the St. Lawrence River in northern New York state. Author: User:Moondigger

Figure 5: Land reclamation – restored land at the Seneca Yoast coal mine. Author: Peabody Energy, Inc.

Mine Safety and Health

Mine Safety and Health

Recent Culture of Prevention in Mining was achieved by a combination of increased society awareness, tougher mining laws and enforcement, higher standards for practices and procedures, systematic management approach and focus on people management.

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Figure 1: Negative pressure full face mask

In addition to any relevant state and local regulations, mines in the United States are also subject to federal regulation; the US Department of Labor’s Mine Safety and Health Administration (MSHA) is the regulatory agency. A list of federal regulations pertaining to mine safety and health are contained in the Code of Regulations (CFR). The specific volume is referred to as Title 30, which is further subdivided based by Part and Sections for specific statues. MSHA uses four principal indices for measuring mine safety: (1) fatal incidence rate (fatal RI), (2) nonfatal incidence rate resulting in days los (NFDL IR), (3) injuries with no days lost incidence rate (NDL IR), and 4) severity measure (SM) (Adapted from Bise, 2003).

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Figure 2: Alert about use of cell phones 

Typically, the development of safety system is based on the following key elements:

  • Safety data review;
  • Benchmarking (evaluate industry performance and compliance requirements);
  • Define goals and objectives;
  • Map current challenges and opportunities;
  • Selection of key performance indicators;
  • Risk Assessment;
  • Develop action plan and safety groups for improvement;
  • Audit/inspection checks;
  • Measure of effort and results;
  • Routine management / Review action plan and training requirements;

Additionally, the foundation of any effective safety system requires commitment, systematic approach, effective people Management (eliminate unsafe acts) and safety engineering (eliminate unsafe conditions).

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Figure 3: Mine Rescue team in training

Serious hazards will always exist in mining…As mining professionals, we need to anticipate safety issues, plan to eliminate or reduce their impact, monitor them to ensure they do not adversely affect miners, and make mining system adjustments to address those that do appear – Mine Safety and Health begins with Good Planning and Well-designed Mines. Moreover, Risk Assessment is a crucial early phase in the risk management planning cycle and it is essential in determining what mitigation measures should be taken to reduce future losses (Adapted from Karmis and Grayson, 2001).

About 80 to 95% of accidents involve some type of unsafe behavior. However unsafe behavior may not be the employee’s fault. Some of the key elements for successfully managing people towards a safer environment includes: Selection & Hiring; Integration and training & re-training; Data-based interventions & performance evaluation; Communication & feedback; Professional development & Organizational behavior;

Five Principles of Safety according Boling (1995) are:

  • All accidents are preventable;
  • All levels of management are responsible for safety;
  • All employees have the responsibility to themselves, their coworkers, and their family to work safely;
  • Management must ensure that all employees are property trained on how to perform every task safely and efficiently;

“Mining Professionals should have as goal for the Industry: Make it a model of excellence in all respects – a shining image of accomplishment” (Adapted from Karmis, Grayson and Watzman, 2001).

Some examples of safe mining practices Includes:

  • Safe Blasting Design and Planning: It is paramount to establish blasting plans in accordance with sound engineering design aligned with the short term mine plan and production needs. The blasting specification and design must be tailored for each blast, in view of the conditions on the site, including experience gained from previous blasts at the quarry, any unusual circumstances which are present or likely to arise, desirable characteristics of the blasted rock, etc.

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    Figure 4: Blasting with potential for flyrocks

  • Safe Mechanical Extraction & Loading Haulage and Dumping Planning: The whole process is associated to three subsystems: Environment, Equipment and People:
    • (1) The work environment includes mine site characteristics such as road design and maintenance, wheatear and climate, and time of day. Road widths, road alignments, lines of sight, intersections, grades, and curves must be designed and maintained with consideration to the largest equipment using the system;
    • (2) Keeping equipment in optimum operating conditions means that they will perform within expected ranges. Equipment systems and tires (rolling material) must be properly maintained;
    • (3) Operator is the vital component of mobile equipment safety. Operators and workers around mobile equipment must be given the tools and skills required to complete tasks safely and efficiently. This requires training focused on understanding the controls, gauges, and miscellaneous systems unique to the truck. It also requires operational and safety training on vehicle;
  • Safe Crushing Planning: The selection of an appropriate processing circuit for your specific material is one of the most important decisions in the design of a processing plant. The layout and design should:
    • Ensure that the risk of any accident or injury is as low as reasonably practicable, and should state any special precautions required to achieve this;
    • Minimize the risk of negative effects of these operations on working conditions and environment (e.g. dust, noise, pollution, etc.);
    • Enable efficient production practices;
    • Ensure that working conditions are safe and sound;
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Figure 5: Dust sampling program

 Could you indicate other challenges and opportunities associated with the future of Mine Safety and Health?

Challenges:

  • Continuing problems in small mines and some contractors;
  • Aging workforce // Period of intense retirements (North America);
  • Rapid influx of new and inexperienced workers;

Opportunities: 

  • Developing deeper understanding of work situations;
  • Linking group and individual behaviors to these situations;
  • An enhanced capability to sift through more powerful databases that better frame and target using;
  • Virtual reality, new simulation and surveillance tools;
  • Involving mine operators, labor, government, and other parties in partnerships that focus on the most pressing needs;
  • Employing new mining methods and new technologies and ways of organizing work more effectively;

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Bise, C. J., et al.” Mining Engineering Analysis”, Society for Mining, Metallurgy, and Exploration, Inc, Second Edition, Denver, CO. (2001).

Lowrie, R. L., et al.,“ SME Mining Engineering Handbook”, Society for Mining, Metallurgy, and Exploration, Inc, Second Edition, Denver, CO. (2002).

Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA, (August, 2002).

Barksdale, R. D., et al., “The Aggregate Handbook”, National Stone, Sand and Gravel Association, Arlington, VA. Fourth Edition (2001).

Karmis, M., et al., “Mine Health and Safety Management”, Society for Mining, Metallurgy, and Exploration, Inc, First Edition, Denver, CO. (2001).

Photos Credit:

Feature: Chilean miners in 2007. Author: National Institute for Occupational Safety and Health

Figure 1: Negative pressure full face masks, possible APF decreased from 100 to 10. Author: US Occupational Safety & Health Administration

Figure 2: Cell Phones and Mobile Equipment Don’t Mix. Author: MSHA Alliance Program

Figure 3: Mine Rescue Instruction Guides Author: MSHA

Figure 4: Flyrock Dangers: MSHA

Figure 5: Mining Engineer taking a reading of dust count in restorable dust sampling program. Author: United States. Bureau of Mines

 

Traditional Surface Mining Methods

Traditional Surface Mining Methods

Surface mining is the predominant exploitation procedure worldwide. Approximately, more than 90% of all non-metallic minerals and metallic minerals and more than 60% of coal are mined by surface methods. Over 30 billion tonnes of ore and waste materials that are mined each year and surface mining accounts for nearly 25 billion tonnes. The subsurface of the earth is the only source for fossil energy and mineral products, and mining is the only way to get at them (Adapted from Ramani, 2012).

Extraction of mineral or energy resources by operations exclusively involving personnel working on the surface without provision of manned underground operations is referred to as surface mining. While an opening may sometimes be constructed below the surface and limited underground development may occasionally be required, this type of mining is essentially surface-based. Traditional surface mining can be classified into two groups on the basis of the method of extraction: Mechanical extraction or aqueous extraction. The primary differences between these mining methods are the location of the ore body and the mode of mechanical extraction. (Adapted from Yamatomi and Okubo, 2009; Hartman, 2002 and Sharma, 2011).

Mechanical surface mining methods Includes:

  • Open-pit mining: Open-pit mining is employed to remove hard rock ore (mostly metallic ore) that is disseminated and/or located in deep seams and is typically limited to extraction by shovel and truck equipment. Many metals are mined by the open pit technique: gold, silver and copper, to name a few.
  • Quarrying: It is a term used to describe a specialized open-pit mining technique wherein solid rock with a high degree of consolidation and density is extracted from localized deposits. Quarried materials are either crushed and broken to produce aggregate or building stone, such as dolomite and limestone, or combined with other chemicals to produce cement and lime. Construction materials are produced from quarries located in close proximity to the site of material in order to reduce transportation costs. Dimension stone such as flagstone, granite, limestone, marble, sandstone and slate represent a second class of quarried materials. Dimension stone quarries are found in areas having the desired mineral characteristics which may or may not be geographically remote and require transportation to user markets.
  • Strip mining: “Open-cast mining” techniques relate to the extraction of ore bodies that are near the surface and relatively flat or tabular in nature and mineral seams. It uses a variety of different types of equipment including shovels, trucks, drag lines, bucket wheel excavators and scrapers. Most strip mines process non-hard rock deposits. Coal is the most common commodity that is strip mined from surface seams.
  • Auger mining: It is a surface mining technique used to recover additional coal from a seam located behind a highwall produced either by stripping or open-pit mining. Auger mining is especially employed when contour strip mining has been exhausted and the removal of overburden to access additional coal no longer becomes economically feasible.
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Figure 1: Surface coal mine in Gillette, Wyoming, USA

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Figure2: Large Limestone Quarry, Ontario, Canada

Aqueous surface mining methods can be subdivided in Placer and Solution and Includes:

  • Placer: concentrations of metals such as gold, titanium, silver, tin and tungsten are washed from within an alluvial deposit.
  • Hydraulic mining: “Hydraulicking” applies high pressure water spray to excavate loosely consolidated or unconsolidated material into a slurry for processing. Hydraulic methods are applied primarily to metal and aggregate stone deposits, although coal, sandstone and metal mill tailings are also amenable to this method. Water supply and pressure, ground slope gradient for runoff, distance from the mine face to the processing facilities, degree of consolidation of the mineable material and the availability of waste disposal areas are all primary considerations in the development of a hydraulic mining operation.
  • Dredging: When hydraulic mining occurs underwater it is referred to as dredging. In this method a floating processing station extracts loose deposits such as clay, silt, sand, gravel and any associated minerals using a bucket line, dragline and/or submerged water jets. The mined material is transported hydraulically or mechanically to a washing station which may be part of the dredging rig or physically separate with subsequent processing steps to segregate and complete processing. While dredging is used to extract commercial minerals and aggregate stone, it is best known as a technique used to clear and deepen water channels and floodplains.
  • Solution: It is applied to the process of removing a soluble mineral by dissolving it and leaching it out.
  • Surface Techniques and In-situ Leaching: Both are applicable to deposit of minerals that can be recovered usually by dissolution, but also by melting, leaching, or slurrying. The two methods are similar and are differentiated primarily through the location and the type of minerals recovered. Surface leaching generally employs heap (or dump) leaching of mineral values; copper, gold, silver, and uranium are common examples. In-situ mining specifically uses barren solution, introduced down by a set of wells. The loaded solution then returns to the surface through concentric or other set of wells. Chemicals and/or bacteriological reagents usually are mixed with water in order to selectively dissolve the valuable minerals.
  • Evaporite (or salt) Mining: In solution mining, fresh water is injected through a pipe into deep shafts that end in the salt beds, and salty water (brine) is drawn upward and dried, to recrystallize the salt. Or, salty brine found in shallow wells can simply be pumped to the surface and dried there, to make salt.
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Figure 3: Dredge no. 3, Klondike River, Canada

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Figure 4: Cyanide leaching Heap, Nevada, USA

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Figure 5: Hydraulic Mining

Mining conditions are likely to be more difficult in the future. While finding a world class mineral deposit cannot be ruled out, if history is a guide, future discoveries will be deeper, thinner, lower grade and have severe conditions, all increasing the difficulty of mining and processing. Therefore, operators should continuously re-evaluate traditional surface mining methods, incorporating new technologies and practices. Hybrid and new methods will be required for delivering economic results and efficiency when approaching these new mineral deposits (Adapted from Ramani, 2012).

How can autonomous equipment and vehicles be applied to mining? Are there opportunities to enhance this application by the use of telemetry and artificial intelligence?

Mining Automation

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Ramani, R. V.” Surface Mining Technology: Progress and Prospects”, 1st International Symposium on Innovation and Technology in the Phosphate Industry, Published by Elsevier Ltd. (September, 2012).

Darling, P.,“ SME Mining Engineering Handbook”, Society for Mining, Metallurgy, and Exploration, Inc, Third Edition. (2011).

Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA, (August, 2002).

Okubo S. and Yamatomi, “Underground Mining Methods and Equipment, Civil Engineering- Vol. II, Encyclopedia of Life Support System (EOLSS), EOLSS Publishers/UNESCO (2009).

Sharma, P. D., “Coal and Metal (Surface and Underground) Mining –  An Overview”, Weblog of Partha Das Sharma. (2011). Last accessed on 07/23/2016 at https://miningandblasting.files.wordpress.com/2009/09/coal_and_metal_surface_and_underground_mining_an_overview.pdf

Dunbar, W. S., “Basics of Mining and Mineral Processing”, Americas School of Mines, University of British Columbia, PWC. (2012). Last accessed on 07/23/2016 at https://www.pwc.com/gx/en/mining/school-of-mines/2012/pwc-basics-of-mining-2-som-mining-methods.pdf

RitchieWiki Team, “Underground Mining”, Ritchie Bros. Auctioneers (2012). Last accessed on 07/23/2016 at https://www.pwc.com/gx/en/mining/school-of-mines/2012/pwc-basics-of-mining-2-som-mining-methods.pdf

Photos Credit:

Feature: Bingham Canyon copper mine, UT, USA: Rio Tinto, Kennecott Utah Copper Corp. Author: Spencer Musick.

Figure 1: A surface coal mine in Gillette, Wyoming. Author: Greg Goebel

Figure 2: Limestone Quarry. Author: Mike Pierce

Figure 3: Dredge no. 3, working in the Klondike River, May the 31st, 1915. Author: Frank and Frances Carpenter collection

Figure 4: Cyanide leaching “heap” at a gold mining operation near Elko, Nevada. Author: U.S. Fish and Wildlife Service

Figure 5: Hydromonitor – Hydraulic mining. Author: Paesslergung

 

Underground Mining Methods

Underground Mining Methods

Underground mining is the process of extracting minerals and ores that are located too far underground to be mined efficiently using surface mining methods.  The primary objective of underground mining is to extract ore safely and economically while minimizing handling of waste rock. Typically, underground mine has less environmental impact. However, it is often more costly and may entail greater safety risks for workers than surface mining. There are several different methods of underground mining. The selection of underground mining methods is primarily based on a set of factors associated with geology of the deposit (e.g. Geometry, quality of rock and ore variability) and economics. Moreover, Candidate methods can therefore be chosen and ranked based on estimated operational/capital cost, production rates, availability of labors and materials/equipment, and environmental considerations. The method offering the most reasonable and optimized combination of safety, economics, and mining recovery is then chosen.

Reflecting the importance of ground support, underground mining methods are categorized in three classes on the basis of the extent of support required: unsupported, supported and caving (Adapted from Okubo and Yamatomi, 2005; RitchieWiki Team, 2009).

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Figure 1: Underground mining methods

The unsupported methods of mining are used to extract mineral deposits that are roughly tabular (plus flat or steeply dipping) and are generally associated with strong ore and surrounding rock. These methods are termed unsupported because they do not use any artificial pillars to assist in the support of the openings. However, generous amounts of roof bolting and localized support measures are often used.

  • Room-and-pillar mining is the most common unsupported method, used primarily for flat-lying seams or bedded deposits like coal, trona, limestone, and salt. Support of the roof is provided by natural pillars of the mineral that are left standing in a systematic pattern.
  • Stope-and-pillar mining (a stope is a production opening in a metal mine) is a similar method used in non-coal mines where thicker, more irregular ore bodies occur; the pillars are spaced randomly and located in low-grade ore so that the high-grade ore can be extracted. These two methods account for almost all of the underground mining in horizontal deposits in the United States and a very high proportion of the underground tonnage as well. Two other methods applied to steeply dipping deposits are also included in the unsupported category.
  • Shrinkage stoping is the method characterized by the mining advance being upward, with horizontal slices of ore being blasted along the length of the stope. A portion of the broken ore is allowed to accumulate in the stope to provide a working platform for the miners and is thereafter withdrawn from the stope through chutes Shrinkage stoping is more suitable than sublevel stoping for stronger ore and weaker wall rock.
  • Sublevel stoping differs from shrinkage stoping by providing sublevels from which vertical slices are blasted. In this manner, the stope is mined horizontally from one end to the other.
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Figure 2: Room-and-pillar

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Figure 3: Shrinkage Stoping

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Figure 4: Sublevel Stoping

Supported methods of mining are often used in mines with weak rock structure.

  • Cut-and-fill is the most common of these methods and is used primarily in steeply dipping metal deposits. The cut-and-fill method is practiced both in the overhand (upward) and in the underhand (downward) directions. As each horizontal slice is taken, the voids are filled with a variety of fill types to support the walls. The fill can be rock waste, tailings, cemented tailings, or other suitable materials. Cut-and-fill mining is one of the more popular methods used for vein deposits and has recently grown in use.
  • Square-set stoping also involves backfilling mine voids; however, it relies mainly on timber sets to support the walls during mining. This mining method is rapidly disappearing in North America because of the high cost of labor. However, it still finds occasional use in mining high-grade ores or in countries where labor costs are low.
  • Stull stoping is a supported mining method using timber or rock bolts in tabular, pitching ore bodies. It is one of the methods that can be applied to ore bodies that have dips between 10° and 45°. It often utilizes artificial pillars of waste to support the roof.
  • Vertical Crater Retreat (VCR) can be either a supported or unsupported method based on the carter blasting technique in which powerful explosive charges are placed in large-diameter holes and fire. Part of the blasted ore remains in the stope over the production cycle, serving as temporary support for the stope walls.
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Figure 5: Cutting and fill

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Figure 6: VCR

Caving methods of mining are varied and versatile and involve caving the ore and/or the overlying rock. Subsidence of the surface normally occurs afterward.

  • Longwall mining is a caving method particularly well adapted to horizontal seams, usually coal, at some depth. In this method, a face of considerable length (a long face or wall) is maintained, and as the mining progresses, the overlying strata are caved, thus promoting the breakage of the coal itself.
  • Sublevel caving is employed for a dipping tabular or massive deposit. As mining progresses downward, each new level is caved in into the mine openings, with the ore materials being recovered while the rock remains behind.
  • Block caving is a large-scale or bulk mining method that is highly productive, low in cost, and used primarily on massive deposits that must be mined underground. It is most applicable to weak or moderately strong ore bodies that readily break up when caved. Both block caving and longwall mining are widely used because of their high productivity.
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Figure 7: Longwall

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Figure 8: Sub-level caving

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Figure 9: Block Caving

There are examples of deposits which can be mined first by surface mining, and then, as the pit deepens, by underground methods. Some deposits are even exploited simultaneously by both methods, typically during the transition period between open pit to underground. Also, every underground mining method requires a point of entrance from the surface (e.g. adit, mine shaft, or vertical or horizontal tunnel). This entry is a key element of the development phase associate with underground mining. (Adapted from Shinobe, 1997; Hartman and Mutmansky – 2002; Dunbar, 2012)

What is the most popular method for underground limestone mines in US?

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Shinobe, A.,“Economics of Underground Conversion in an Operating Limestone Mine” M.Sc. Thesis, McGill University, Montreal, Canada. (1997).

Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA , (August, 2002).

Okubo S. and Yamatomi, “Underground Mining Methods and Equipment, Civil Engineering- Vol. II, Encyclopedia of Life Support System (EOLSS), Tokyo, Japan. 23 pp. (2005).

Dunbar, W. S., “Basics of Mining and Mineral Processing”, Americas School of Mines, University of British Columbia, PWC. (2012). Last accessed on 07/21/2016 at https://www.pwc.com/gx/en/mining/school-of-mines/2012/pwc-basics-of-mining-2-som-mining-methods.pdf

Hustrulid W. A. and Bullock, R. L., “Underground Mining Methods: Engineering Fundamentals and International Case Studies”, Editors, W.A. Hustrulid and R.L.Bullock, Society for Mining, Metallurgy, and Exploration, Inc.(SME) 8307 Shaffer Parkway, Littleton, CO, USA 80127,  718 pages. (2001).

Brady, B.H.G., Brown, E.T., “Rock Mechanics for Underground Mining” 3rd edition reprinted with corrections, Springer, Dordrecht, NL (2006).

Bullock, R. L., “Notes on Underground Mining Methods and Equipments (Mi Eng 324)”, Missouri University of Science and Technology, Rolla, MO, USA,  (2010).

RitchieWiki Team, “Underground Mining”, Ritchie Bros. Auctioneers (2012). Last accessed on 07/21/2016 at https://www.pwc.com/gx/en/mining/school-of-mines/2012/pwc-basics-of-mining-2-som-mining-methods.pdf

Photos Credit:

Feature: Shearer at work in a coal mine. Author: http://www.eickhoff-bochum.de/de/

Figure 1: Underground mining methods. Author: Brady and Brown, 2006

Figure 2: Room-and-pillar. Author: Hustrulid and Bullock, 2001

Figure 3: Shrinkage stoping. Author: Hustrulid and Bullock, 2001

Figure 4: Sublevel stoping. Author: Hustrulid and Bullock, 2001

Figure 5: Cutting and fill. Author: Hustrulid and Bullock, 2001

Figure 6: VCR. Author: Hustrulid and Bullock, 2001

Figure 7: Longwall . Author: Hustrulid and Bullock, 2001

Figure 8: Sub-level caving. Author: Hustrulid and Bullock, 2001

Figure 9: Block caving. Author: Hustrulid and Bullock, 2001

Mining Projects:  Exploitation Phase & Methods of Mining

Mining Projects: Exploitation Phase & Methods of Mining

Once a mining company has constructed access roads and prepared staging areas that would house project personnel and equipment, mining may commence. Typically, production levels are during which production is gradually increased towards design capacity within the transition period after development.  It is not uncommon commissioning period, sometimes over 12 months in the mining industry.

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Figure 01: Open pit diamond mine of Mirny in Yakutia

Although all types of active mining share a common aspect: the extraction and concentration (or beneficiation) of a metal from the earth, proposed mining projects differ considerably in the proposed method for extracting and concentrating the metallic ore (Adapted from Miller et al., 2016).

Exploitation in the life of a mine, is not only the culmination of the three preceding stages (e.g. prospecting, exploration and development), but the end process by which the three previous starts and the fifth stage, reclamation, are economically justified. Basically, exploitation is the work of recovering mineral from the earth in economic amounts and delivering it to shipping or processing facilities. Therefore, exploitation or production phase are associated with the daily activities of obtaining (extracting) a saleable product from the mineral reserve on a commercial scale, including any processing before sale. Although some exploration and development may continue, the emphasis in the exploitation stage is on production of marketable minerals. Usually, only enough exploration and development are done prior to exploitation to ensure that production, once started, can continue uninterrupted throughout the life of the mine. In the mining production process, a number of extractive unit operations are employed, the primary ones constituting the production cycle and the secondary ones the auxiliary or support operations (Adapted from Hartman and Mutmansky, 2002).

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Figure 02: Udachnaya diamond mine, Russia

Selection of an appropriate mining method is a complex task that requires consideration of many technical, economic, political, social, and historical factors. The appropriate mining method is the method which is technically feasible for the ore geometry and ground conditions, while also being a low-cost operation. This means that the best mining method is the one which presents the cheapest problem.

Characteristics that have a major impact on the mining method selection include:

  • Physical and mechanical characteristics of the deposit such as ground conditions of the ore zone, hangingwall, and footwall, ore thickness, general shape, dip, plunge, depth below the surface, grade distribution, quality of resource, etc. The basic components that define the ground conditions are: rock material shear strength, natural fractures and discontinuities shear strength, orientation, length, spacing and location of major geologic structures, in situ stress, hydrologic conditions, etc;
  • Economic factors such as: capital cost, operating cost, mineable ore tons, orebody grades and mineral value;
  • Technical factors such as: mine recovery, flexibility of methods, machinery and mining rate;
  • Productivity factors such as annual productivity, equipment, efficiency and environmental considerations;
  • Environmental and Social factors: The physical, social, political, and economic climate must be considered and will, on occasion, required that a mining method be rejected because of these concers;

Each of these criteria can become the principal determining factor in method selection, but the obvious predominance of one consideration should not preclude careful evaluation of all parameters (Adapted from Bitarafan and Ataei, 2004).

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Figure 03: Access to underground mine

The strategy for conducting the exploitation stage of mining should be clear as mineral production begins. The cardinal rule of exploitation is to select a mining method that matches the unique characteristics (natural, physical, geologic, social, political, etc.) of the mineral deposit being mined, subject to the requirements of safety, mineral processing, and the environment, to yield the overall lowest cost and return the maximum profit. In stating this basic objective, health and safety of working conditions and community, environment protection and economic development of the local community must all be accorded the highest level of concern (Adapted from Hartman and Mutmansky, 2002).

Traditional exploitation methods can be classified into two broad categories based on locale: surface or underground. Surface mining includes mechanical excavation methods such as open pit and open cast (strip mining), and aqueous methods such as placer and solution mining. Underground mining is usually classified in three categories of methods: unsupported, supported, and caving.

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Figure 04: Coal mining, Lower Lusatia

It is critical to capture the benefits of the learning curve experienced within the first years of production. Even the best designed and planned mines will inevitably require changes along the way due to unanticipated issues and/or better knowledge of the deposit and required mining processes. The speed and effectiveness of these adjustments will make a significant difference to the initial profitability of the mining enterprise.

Recently, there have been multiple innovative methods and approaches to mining. Do you know what Asteroid mining is?

Kind regards,

Ronaldo

Follow me on twitter @rcrdossantos

References:

Miller, G. et al. ,”Guidebook for Evaluating Mining Project EIAs”, Environmental Law Alliance Worldwide (ELAW), University of Nevada at Reno, (July 2010). Last accessed on 06/05/2016 at https://www.elaw.org/files/mining-eia-guidebook/Full-Guidebook.pdf

Bitarafan, M.R. and Ataei, M. “Mining method selection by multiple criteria decision making tools”, The Journal of The South African Institute of Mining and Metallurgy, (October, 2004).

Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA , (August, 2002).

Photos Credit:

Feature: Absetzer im Tagebau Hambach. Author: Elsdorf-blog.de

Figure 01: The open pit diamond mine of Mirny in Yakutia. Author: Vladimir

Figure 02 : Udachnaya Diamond Mine, Russia.    Author: Stapanov Alexander

Figure 03: The Darkness Mine Stone. Author: Darius Sankowski

Figure 04: Pit Mining Brown Coal Lower Lusatia. Author: AFOK14