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By D. R. Shoemaker, H. W. Judges

A 16.5-kt/d underground molybdenum mine is being developed at Questa in northern New Mexico by Molycorp Inc., a wholly-owned subsidiary of Union Oil Company of California. The new $200-million underground project will revitalize mining and milling activity at Questa, where small scale underground mining first began in 1920. Large scale open-pit mining was initiated in 1965 but now, because of the high stripping ratio, surface mining is being phased out. Construction of the underground mine began in 1979, and first produc¬tion is scheduled for early 1983. The company expects full capacity-9 Gg of molybdenum per year-to be reached in 1984.

Jan 6, 1980

By Louis W. Cope

Mongolia is known in western countries as the location of rich dinosaur fossil fields. However, the country is even richer in mineral resources. The Ministry of Industry and Trade reports 6,000 mineral occurrences of 80 metals and minerals. Mongolia has already attracted much foreign investment in the mining sector. Mining is the country’s largest industry. It is responsible for 17 percent of the gross domestic product, 65 percent of industrial output and 57 percent of export earnings.

Jan 1, 2006

By R. Tamblyn

Vertically stirred media mills are a highly effective low-footprint solution for the ultrafine grinding of industrial minerals. This work investigates the effect of media density on flow patterns within the mill. Direct irradiation of a media particle leads to decay through positron emission, consequently forming two anti-parallel gamma rays, which allow for the real time tracking of particle position. Grinding media of the same size, but with a range of specific gravities are followed using this method, and the effect on the flow within the mill is revealed. The technique is seen to be an effective method to highlight the velocity profiles within the mill, as well as the zones where grinding is less efficient ? areas of relatively low velocity and high residence time. The changing media is seen to effect the overall flow patterns within the mill, having consequential effects on the efficiency of the grind.

Jan 1, 2009

By AMIR EHSAN KIANFAR, Moritz Ziegler, TOBIAS HARTMANN, ELISABETH CLAUSEN

Accurate positioning information is a central step in the process of increasing automation and digitalization in the mining industry. Underground mine environments are prime examples for GNSS-denied environments that pose several additional challenges for the employed indoor positioning system (IPS). This work presents an ultra-wideband (UWB)–based system specifically tailored for underground mine environments. Initially, the UWB technology is reviewed and basic concepts of IPS are explained. Both software and hardware are described in detail, including positioning algorithms, electrical circuitry, and the mining-compatible enclosure. Finally, the results from field tests in an underground mine are presented and positioning performance and the influence of dilution of precision (DOP) on positioning results are empirically evaluated. The results show that the localization errors are mostly below 1 m. Individual zones of high localization errors are suspected to be caused by noise interference. Significant DOP influence due to the mining drift geometry can be confirmed. The system shows promising localization results for different mining applications, while influences negatively impacting the accuracy are presented as items for future research.

Jul 7, 2023

By Ryan C. Stephan, Christopher Mark

"Some of the weakest roof in United States coal mines is found in the Illinois Basin. Historically, the Illinois Basin has also suffered from high rates of unplanned roof falls and rock fall injuries. During the past decade, however, roof fall and rock fall injury rates have fallen dramatically, and are now lower than the national average. Several technologies are responsible for the improvement. Roof screen was rarely used ten years ago, but a number of mines now use it on a regular basis to prevent rock falls and rock fall injuries. Other roof skin control fixtures and work practices have contributed as well.The reduction in roof falls is also directly attributed to enhanced intrinsic roof support. Stiffer primary bolting patterns have reduced the magnitude of roof spalling and roof sag. They have also helped create a more intact beam that is able to be suspended from longer cable bolts. Cable bolt design methodology has also contributed to this reduction in roof falls. Some early cable bolt applications were unsuccessful because they employed as few as two cable bolts per intersection. This paper describes a methodology for estimating rock loads for support design.ROOF FALL TRENDS IN THE ILLINOIS BASINAlthough the Illinois Basin has a long history of poor roof conditions and high rates of unplanned roof falls and rock fall injuries, recent data indicates a change in the trend. Roof fall rates are determined by dividing the total number of non-injury roof falls by the total number of hours worked underground. The data is considered for 200,000-man hours. While the Illinois Basin was once a coalfield experiencing roof falls at nearly twice the national average, it is now at or below the national rate. Figure 1 indicates the trend over the past 20 years. In 2008, the Illinois Basin mines experienced 5.06 roof falls every 200,000-man-hours, compared to only 0.75 in 2018.There has also been a significant reduction in the rate of rock fall injuries in the Illinois Basin coal mines, as shown in Figure 2. In 2008 there were 1.48 rock fall injuries every 200,000-man-hours, compared to only 0.43 in 2018.ILLINOIS BASIN COAL ROOF GEOLOGYThe roof rock in the Illinois Basin has been studied in the past to understand the primary causes of roof failures (Molinda et al., 2008; Thompson, 2010; Molinda and Mark, 2010). Rusnak and Mark (2000) evaluated 10,000 laboratory strength tests from 800 rock units and concluded that for shale, siltstone, and sandstone, the strength of the Illinois Basin variety was less than half that of the same rock types in Central Appalachia (Figure 3). A study of Coal Mine Roof Rating (CMRR) measurements in more than 200 US coal mines also found that weak roof was predominant in the Illinois Basin (Mark and Molinda, 2005)."

Jan 1, 2019

By Donald P. Richards

Is a shaft the same as a tunnel and can it be approached in the same manner for design and construction? The most obvious difference between a shaft and a tunnel is that of orientation; whereas a tunnel is commonly near horizontal or slightly dipping, a shaft is commonly vertical or steeply inclined. As a result, design and construction methods employed for tunneling, in general, cannot be directly applied to shafts, although some of the basic concepts of behavior are quite similar. Many of the shafts that have been sunk in various parts of the world are owned by private mining companies. Each company has generally accumulated years of experience in shaft sinking and mining techniques pertinent to its particular geographic location. When a new shaft is to be sunk or an existing shaft deepened, the tendency often seems to be to continue to use the methods that have been used successfully in the past.

Jan 1, 1979

By K. Heasley, A. Yassien, A. Khair, S. Peng

There are three major components of a fully grouted roof bolt which primarily determine its ability to develop and sustain load: the steel rebar, the resin annulus, and the rock/grout interface. The untensioned, fully grouted roof bolt is subjected to loading only when the surrounding rock deforms. Vertical rock deformation is generally a result of strata sagging and bedding plane separation, whereas horizontal deformation is typically a result of bedding plane sliding. These two types of deformation create different types of internal loads with-in the roof bolt, tensile stress for vertical rock deformations and shear stress for horizontal rock deformations. Also, as a result of the mutual load transfer between the rock and bolt, shear stress will be developed along the grout/rock interface. According to the exact bolt loading conditions, different failure modes may occur: bolt axial failure, bolt shear failure, and shear failure along the grout/rock interface. Understanding these possible failure modes and their root causes is the key to eliminating roof failures in underground mines employing fully grouted resin bolts. Using ABAQUS 5.8, a finite element model was developed to simulate the components of the fully grouted bolt and its interaction with the surrounding roof strata. Several models were conducted to investigate how load transfer occurs between the rock and the bolt under different geological and mining conditions. The effects of bed-ding plane location and properties, and strata sequence on bolt stability were studied. Also, the effects of hole roughness on bolt stability were discussed. Bolt axial failure was not observed within the range of the studied parameters; however, a combination of high overburden depth, a bedding plane located at 2 to 3 ft from the roofline or a low coefficient of friction along the bedding plane caused strata sliding and shears failure in the bolt. Also, in the case of a weak immediate roof, the shear stress at the grout/rock interface could exceed its ultimate capacity lead to slippage.

Jan 1, 2004

The ventilation conditions at the underground coal mines are influenced; first: by the disturbances of the natural nature (barometric pressure, methane liberation, etc.), and second: by the disturbances caused by the production process. The major goal of this study was to determine the changes of the ventilation parameters, such as the flow, pressure and methane concentration around the longwall panel, particularly, along the longwall face due to the shearer operation (motion). It is well known from the practice, that the movement of the shearer influences the ventilation parameters around the longwall panel, including the gob area. Until now, these data were gathered in a single or multiple locations at the different time. However, only the simultaneous measurements of all of these values allow seeing the time dependent interrelationships between measured parameters. To be able to show these interrelationships, special experiments, described in this paper, were carried out by the author. These experiments were prepared and executed at the BUDRYK Coal Mine in Poland. During each experiment a simultaneous measurements and monitoring of the barometric pressure, air velocity and methane concentration at the different locations along the longwall face, were performed. The investigation was possible by using a special setup of instruments with a short sampling time, i.e., within 2 seconds. The monitoring of the absolute pressure was conducted by using the digital barometer µBar, developed by EMAG, based on the SETRA pressure transducer, model 470. The velocity of air was measured using the electronic vane-anemometers, developed by IMG-PAN. The methane concentrations were measured using methanometers as the part of the EMAG automatic gas monitoring system. The investigation data confirmed that disturbances due to the operation (motion) of the shearer at the longwall face have a local character. It could be also seen that a large diameter shearer (compared to the total cross-section area available for the air flow) is acting as the piston compressing the air (the overpressure) ahead of the shearer. This fact affects the methane mixing process and flow patterns in the vicinity.

Jan 1, 2009

By Judy B. Jones, Bradley A. Crenshaw, Theodore DePooter

This paper reviews groundwater issues leading to a secondary grouting program at the Chattahoochee Tunnel that was implemented subsequent to the contact grouting program. The secondary grouting program was developed based on infiltration data, geology, and testing programs. This paper includes a brief description of the geological features encountered, as well as describing the grouting program. The success of this grouting operation has been quantified by several methods, and is presented to help others project the costs and benefits of this type of program. Review of initial results and refinements of techniques are also discussed.

Jan 1, 2005

Ion exchange (IX) has been in use for a long time, references to IX are made in The Bible, Exodus Chapter 15 vs. 22-25 ?and the waters were made sweet?.1, 2 Aristotle noted a reduction in the salt content of water when passed through certain types of sand, a phenomena probably associated with ion exchange characteristics of zeolites. Some major milestones in IX development include; ? ~ 1400 BC Moses ? ~ 330 BC Aristotle ? 1850 the discovery of the IX process3 ? 1909 Gans proposed zeolites for gold recovery ? 1935 sulfonated coals used for water softening ? 1939 copper recovery from Rayon Production ? 1940 The Rare Earth Project at Ames ? 1952 first South African U IX mine at West Rand (first SX of U using amines 1957) ? 1954 first U IX in USA at Shiprock Mine N.M. USA. ? Late 1950?s U IX over 50 fixed bed systems installed in North America ? 1950?s-1960?s FSU introduce U IX both fixed bed and RIP ? 1968 Gold IX (RIP) Muruntau Uzbekistan (CIL wasn?t commercialized until 1973) ? Mid 1970?s FSU & USA independently develop ISL combined with IX for U recovery ? 1978 Chinese Tungsten IX commercial Plant ? 1984 Uranium extraction from seawater ? 2004 Recovery of Gallium using hydroxyamic acid ligands ? Current ? Commercialization of IX for recovery of gold thiosulfate. Ion exchangers can be naturally occurring or synthetic; the majority of ion exchange materials in use today are synthetic resins based upon organic polymers such as polystyrene or methacrylate. Into more modern times the use of ion exchange for metal recovery was first proposed for the recovery of gold using zeolites in 1909.4 In 1939 copper was being recovered from the manufacturing of Rayon using ion exchange5 a development that continued applicability through to current times in the production/recovery of copper and nickel in ammoniacal leach processes. In early 1949 researchers at the Rohm & Haas Company discovered that hexavalent uranium existed as an ionic complex in sulfuric acid leach liquors, and that quaternary ammonium anion exchange resins exhibited a high selectivity for this ionic species6 The first commercial application of this technology went on-stream in October 1952 at the West Rand Consolidated Mines, Ltd operation in South Africa. 7 Ion Exchange has been applied for the recovery and purification of a range of metals;8 ? Uranium, Thorium and transuranic elements ? Rare Earths ? Gold, Silver and platinum group metals (PGM?s) ? Chromium, Copper, Zinc, Nickel, Cobalt ? Refractory Metals; Molybdate, Vanadate, Tungstate, Rhenium Mercury.

Feb 27, 2013

By David Young

This paper presents tunnel design considerations for the SR75/282 Transportation Corridor Project in Coronado, California. The project is managed by the City of Coronado in cooperation with Caltrans and the US Navy and may include a one-mile long twin-tunnel section with two options: a 36.5 foot diameter twin-bored tunnel or a twin cut-and-cover box. The alignment crosses the Coronado Fault, and design provisions were needed at the fault crossing to maintain life safety and prevent rapid inundation of the tunnel in the event of fault rupture. These provisions are discussed along with considerations related to liquefaction and ground shaking. The project is currently in the planning stage with construction to start around 2012.

Jan 1, 2008

Ceremonies for the induction of four mining industry pioneers into the National Mining Hall of Fame will be held Saturday, Sept. 13, 2008 at the Charles F. Barber Pavilion of the Museum Convention Center in Leadville, CO. This will be the 21st Annual National Mining Museum and Induction Banquet. The four inductees are Lew Eklund, 76, Carrie Jane Billings Everson (1843-1914), ?Colonel? William C. Greene (1851-1911) and Arthur L. Hawkesworth (1860-1905). Lew Eklund founded Eklund Drilling that is now based in Elko, NV. He invented many designs that play a major role in today?s mining industry. His Cyclo Blower and various sampling devices he designed helped to revolutionize gold deposit exploration by allowing mining companies to effectively sample microscopic gold. Carrie Jane Billings Everson discovered and proved a method for bulk oil flotation concentration of mineral ores, the precursor to modern froth flotation methods of minerals concentration. She patented her process in 1886. In the early 1890s, coworkers built and operated demonstration plants incorporating her bulk oil flotation process. ?Colonel? William C. Greene was responsible for the development of the great copper mining properties of Cananea, Mexico. In seven years, he went from ragged cattleman and adventurer to the greatest captain of industry the borderlands have ever seen. Arthur L. Hawkesworth was a master mechanic for Anaconda Copper. He invented the detachable drill bit. His invention generated tremendous savings for the mining industry in time, in dollars and in safer operating conditions underground. His bit?s long lasting contribution to improved mine economics is immeasurable. The 21st Annual National Mining Museum and Induction Banquet will begin with an open house and reception at 5:30 p.m. followed by the dinner and program at 7 p.m. The inductions will bring to 201 the number of mining ?greats? whose engraved photographs and biographical sketches are installed in the National Mining Hall of Fame.

Jan 1, 2008

By P. Schilizzi, A. Jarosz, M. Karmis

This paper is concerned with subsidence prediction methods and in particular with two techniques, one based on profile functions and the other on influence functions. Profile function methods provide a tool for a fast calculation of subsidence on a line across a mine panel. Influence function methods, on the other hand, allow for a more detailed calculation of ground movements, in any mode and at any depth, on a grid or at any specific point. In more detail, the hyperbolic tangent profile function, as developed by VPI&SU from field data pertaining to the eastern U.S. coalfields, and an influence function method currently being adapted for the same region, are presented and discussed. The applicability, advantages and limitations of these techniques are examined and comparisons are presented with field measurements. Computer software developed for the application of these prediction methods, for two widely used personal computer systems, are also discussed and a number of examples are presented demonstrating the potential of such programs.

Jan 1, 1986

By Sigurd L. Lamhauge, Karl Gunnar Holter, Svein E. Kristiansen

An innovative sprayable waterproofing membrane in combination with the traditional Nordic method of waterproofing with polyethylene foam sheets was used for the waterproofing of the tunnel. The sprayable membrane was integrated in the final sprayed concrete lining in a sandwich structure, hence constituting a composite water-proof lining based on sprayed concrete. The spray able membrane was applied in areas with small to moderate water ingresses, making up approximately 50% of the total area requiring waterproofing in the tunnel. State-of-the-art application technology with a computerized spraying robot was used. A consistent application of the required thickness at a high speed was thereby achieved.

Jan 1, 2007

By Edward D. Graf

Once the heavy work of mining, supporting and completing an underground structure is finished, there is frequently the problem of handling unwanted water infiltration into the opening. Methods of controlling the infiltration vary from collecting and channelling the inflow to shutting off the water at the surface of the opening or within the ground formation. Discussed are various methods of controlling ground water inflow from within the structure including collector pipe systems, shotcrete, cement grout, bentonite, and various chemical grouts. Case histories illustrating some of the methods and materials will be presented.

Jan 1, 1987

By F. Khorram

Image processing is a technique that simulates the human vision system. This technique enables applying every statistical or intelligent operation to recognize differences. In this way this new technique is used in quality control systems in most industries. Studying sedimentary rocks is very important from the economic point of view. Some units of sedimentary sequences involve different mineral deposits, hydrocarbon and water resources. Therefore it is important to identify and classify different sedimentary rocks. Descriptive classification of sedimentary rocks is usually based on visual and textural features and chemical composition of a sample. In this paper different samples of a limestone mine in central part of Iran are classified. The samples were collected from different parts of the mine and crushed down in size from 2.58 cm to 3.58 cm. The rock samples were labeled based on percentage of chemical and lithological compositions. Each sample was assigned to one of the distinguished groups. The images of the samples were taken in appropriate environment and processed. A total of 74 features were extracted from the identified rock samples in all images. In order to feature dimensional decrease, principal component analysis method was used. Then Bayesian statistical algorithm was used as a useful tool for classification. Classification Correctness Rate (CCR), calculated for the test data sets are %88, %68, %61 and %72 for the first to fourth class respectively. Therefore it can be inferred that the extracted features of images are appropriate indicators for different samples identification. These precise results besides the advantages of image processing technique, which are increasing speed of operation and decreasing cost, appears to be a desirable success.

Jan 1, 2012

By Thomas Sisley, Jozef Zurawski, Richard Switalski

Hilltop Interceptor Contract G is one of the segments of the wastewater control system in the greater Cleveland area. The tunnel is a relief interceptor constructed by the Northeast Ohio Regional Sewer District to minimize combined sewer overflows in the Easterly Service Area. The design study identified the need for a 3.35 m (132 in) diameter, 3.35 km (11,000 ft)in-line storage conveyance tunnel to be constructed at depths of 30 to 70 m (100 to 230 ft).Six structures for access, future flow drop, work shafts and overflow control were required to complete the system. The interceptor reduced the design peak flow from 12.5 m3/s(285 mgd) to 6.1 m3/s (140 mgd) by detaining in line 22,800 m3 (six million gallons) of wastewater.

Jan 1, 1997

By Paul Russell, M. M. Kimberley, Erick F. Welland, Louis Cope, C. C. Mosher, William M. Shepard, William C. Larson, Graham Closs

Exploration activities in 1980 felt the effects of unstable economic conditions and oscillating metal prices. In the cyclical, boom-or-bust precious metals and uranium markets, precious metals activity flourished and uranium was definitely in a slump. By November last year, the price for vellowcake was down nearly $20 from two years earlier. Many mining and milling operations closed, particularly in Wyoming, New Mexico, and Colorado. Decreasing emphasis on nuclear power continued to impact the market, as did the Three Mile Island accident of 1979. Earlier forecasts estimated that 10 to 12 reactors would be ordered per year by US utilities throughout the 1980s, but current forecasts suggest that it may be 1983 or 1984, or even later, before any new US plants are ordered, according to Thomas A. Boyden, vice president of Nuclear Exchange Corp. "Without those new plants, the consumption loss to industry is 4 to 5 million pounds (1.8-2.3 kt) of uranium per year. The cumulative loss to the industry is currently estimated at 25 to 30 million pounds (11.3-13.6 kt)," Boyden said in a May 1980 presenta¬tion. Despite the plunging market, there were a few notable uranium explora¬tion programs: •Exxon expanded uranium exploration in New Mexico, where the company reportedly took preliminary steps toward acquiring mineral rights to a 22-km2 prospect, 19 km south of Santa Fe. • Mountain States Resources began the second phase of an exploratory drilling program on its Sinbad/ Solo prospect in Utah. • Also in Utah, Cotter Corp. drilled its first exploratory hole in the Dirty Devil River district. Exploration for precious metals in 1980, however, appeared to tend toward the opposite extreme. High prices sparked near feverish searches in Alaska, California, Colorado, and Nevada. Numerous mines abandoned years ago were revived with some signs of success. Significant gold finds were reported in California and Nevada: • Homestake Mining Co. announced a gold discovery in California estimated to contain over 5 Mt with an average grade of about 5.8 g/t. Because the deposit consists of finely disseminated particles not visible to the eye, many speculate that prospectors bypassed the area during the 1849 California gold rush. • Newmont Mining Corp. discovered two gold ore bodies-Maggie Creek and Gold Quarry. Maggie Creek reportedly contains an estimated 13.7 t of gold in 4.3 Mt of ore, and Gold Quarry contains about 31.1 t of gold in 9 Mt of low grade ore and 2.3 Mt of higher grade ore. Highlights of this year's exploration review include articles on the modest growth recorded in geophysical activity, technical developments in exploration geochemistry, the variety of new instruments being tested or made available for exploration, and a state-by-state exploration review for the year.

Jan 5, 1981

By James F. Kvitkovich, George V. Weisdack

Editor’s note: This is the second part of a two-part series on longwall mining in the United States. Part one was published in the December 2005 issue of ME (pp. 21-26). It provided a history of longwall coal mining in the United States. It also discussed the technology involved in the productivity gains and operational improvements. Boyd anticipates that U.S. coal production will increase by 61 Mt (67 million st) (6 percent) from 2004 to 2010. A combination of higher surface and underground mine production will be required to meet the projected market demand. Boyd’s projections of coal production by major mining methods are shown in Table 1.

Jan 1, 2006

By H. Lyn Bourne

This is the seventh annual tabulation of royalty information. It is also the first year in which some data have been deleted to make room for new data. The concept of royalties evolved from a time when the government owned all of the land, including mines, to the situation where free miners won the right to claim minerals but paid a portion of their production to the royal treasury. Today, a mineral royalty is a payment to the owner of the mineral rights for the privilege of producing the mineral commodity. However, some people incorrectly believe that the selling price and the royalty are the same thing. The contract between the owner (lessor) and the mining company (lessee) is the mineral lease. Some clauses that are common to mineral leases include: identification of property, granting clause, reservations, definitions, royalty rate, taxes and title, indemnity, termination, inspection, assignability, successors, and reclamation. There often are variations in royalty rates for a given commodity that reflect differences in location, quality, market conditions or public versus private ownership. History In the time of ancient Rome, the government owned the mining properties by virtue of conquest. It would lease the mines to favored citizens who would pay rent to the State. Various conditions of sovereign ownership of both land and mineral rights continued in Europe until the Renaissance. As the laws evolved for land ownership by private citizens, the concept that minerals belonged to the State (King, Crown, sovereign) continued until about the 15th century. Free miners challenged the notion of sovereign ownership and won the right to discover and claim minerals. But a portion of their production had to be paid to the sovereign - a royalty. So, the original concept of a mineral royalty was a tax on production that was due to the Crown or Church. The term mineral royalty, as it is known today, is a payment to the owner of the mineral rights (formerly the royal owner) for the privilege of mining and producing the mineral commodity. The owner of the mineral rights, the lessor, and the mine operator, the lessee, enter into an agreement to mine the property. The agreement is the lease. While this concept is common, there are some who do not understand that the royalty is a portion of production paid to the owner as agreed on in the lease document. This author has seen reports where the selling price of a commodity has been quoted as the royalty. ("They get 70 cents a ton royalty at their pit and the guy down the road only has a 65 cent royalty.") These reports have been authored by people not familiar with the mining industry. Lease clauses In addition to the amount to be paid the lessor, there are several other items to be addressed in the lease agreement. The following list may not be all inclusive, but briefly describes most of the common clauses any good mining lease should contain. Identification: This opening clause names the owner (lessor) and the operator (lessee), the address of each, and gives the legal description of the property. Granting clause: This part of the lease gives the time period or duration of the agreement and information about renewal periods. It also has language about the exclusive right of the lessee to mine the property. Reservations: If the owner wants to exclude any portion of the property or set some specific conditions about the operation, there needs to be a clause that describes these reservations. Definitions: This section should address some of the technical terms that the lessor may find confusing - short tons versus cubic yards, dollars versus percentage of average selling price, any escalator indices such as consumer price index or producer price index, and material mined versus material sold. Royalty: This section spells out what the royalty rate will be, how often it will be paid, if there is an annual minimum, the pay dates, and how the records will be kept. This section also describes the conditions under which the lessee is exempt from the annual minimum - natural disasters, strikes, governmental actions, or other causes referred to as force majeure. Taxes and title: The lease needs to identify who is responsible for the property taxes, severance taxes (if applicable), and other taxes that relate to the mining activity - taxes on equipment, improvements, or stockpiles. This is a good place in the lease for the owner to certify his ownership of the property and its mineral rights and also certify that no other leases are in effect. The lessees may want language that allows them to pay mortgages or other debts on the property to keep their lease in effect. Indemnity: This portion of the lease identifies that the lessee assumes the risks for lessee's mining operation. Lessor should expect indemnification by the lessee through standard insur¬ance policies - workers compensation, liability and property damage. Termination: Both the lessor and lessee want language that will allow them to terminate the lease. This section of the lease describes the conditions under which one of the parties may terminate the lease (failure of the

Jan 1, 1989