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Rules of Thumb for Mining and processing

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    Rules of Thumb for Mining and processing

    Rule Number TopicRule of Thumb1.01DiscoveryIt takes 25,000 claims staked to find 500 worth diamond drilling to find one mine. Source: Lorne Ames1.02DiscoveryOn average, the time between discovery and actual start of construction of a base metal mine is 10 years; it is less for a precious metal mine. Source: J.P. Albers1.03DiscoveryOn average, the time between discovery and actual start of production of a mine in an established mining district (“brown field”) is seven years. Source: Sylvain Paradis1.04DiscoveryOn average, the time between discovery and actual start of production of a mine in a district where there is no previously established mining activity (“green field”) is ten years. Source: Sylvain Paradis1.05CostsThe amount expended on diamond drilling and exploration development for the purposes of measuring a mineral resource should approximately equal 2% of the gross value of the metals in the deposit. Source: Joe Gerden1.06Bulk SampleThe minimum size of a bulk sample, when required for a proposed major open pit mine is in the order of 50,000 tons (with a pilot mill on site). For a proposed underground mine, it is typically only 5,000 tons. Source: Jack de la Vergne1.07Ore Reserve EstimateThe value reported for the specific gravity (SG) of an ore sample on a metallurgical test report is approximately 20% higher than the correct value to be employed in the resource tonnage calculation. Source: Jack de la Vergne1.08Ore Resource EstimateTo determine an “inferred” or “possible” resource, it is practice to assume that the ore will extend to a distance at least equal to half the strike length at the bottom of measured reserves. Another rule is that the largest horizontal cross section of an ore body is half way between its top and bottom. Source: H. E. McKinstry1.09Ore Resource EstimateIn the base metal mines of Peru and the Canadian Shield, often a zonal mineralogy is found indicating depth. At the top of the ore body sphalerite and galena predominate. Near mid-depth, chalcopyrite becomes significant and pyrite appears. At the bottom, pyrite, and magnetite displace the ore. Source: H. E. McKinstry1.10Ore Resource EstimateArchean aged quartz veins are generally two times as long as their depth extent, but gold zones within these vein systems are 1/5 - 1/10 as long as their depth extent. Source: Gord Yule1.11Ore Resource EstimateIn gold mines, the amount of silver that accompanies the gold may be an indicator of depth. Shallow gold deposits usually have relatively high silver ******* while those that run deep have hardly any. Source: James B. Redpath1.12Ore Resource EstimateAs a rule of thumb, I use that 2P (Probable) reserves are only such when drill spacing does not exceed five to seven smallest mining units (SMU). Open pit mining on 15m benches could have an SMU of 15m by 15m by 15m. Underground, an SMU would be say 3m by 3m by 3m (a drift round). Source: René Marion1.13Ore Resource EstimateYour thumb pressed on a 200-scale map covers 100,000 tons of ore per bench (height assumed to be 50 feet). Source: Janet Flinn1.14Strike and DipThe convention for establishing strike and dip is always the Right Hand Rule. With right hand palm up, open and extended, point the thumb in the down-dip direction and the fingertips provide the strike direction. Source: Mike Neumann

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    Arrow Rule Number 2 -Rule of Thumb for Rock mechanics

    .01Ground StressThe vertical stress may be calculated on the basis of depth of overburden with an accuracy of ± 20%. This is sufficient for engineering purposes. Source: Z.T. Bieniawski2.02Ground StressDiscs occur in the core of diamond drill holes when the radial ground stresses are in excess of half the compressive rock strength. Source: Obert and Stephenson2.03Ground StressThe width of the zone of relaxed stress around a circular shaft that is sunk by a drill and blast method is approximately equal to one-third the radius of the shaft excavation. Source: J. F. Abel2.04Ground ControlThe length of a rock bolt should be one-half to one-third the heading width. Mont Blanc Tunnel Rule (c.1965)2.05Ground ControlIn hard rock mining, the ratio of bolt length to pattern spacing is normally 1½:1. In fractured rock, it should be at least 2:1. (In civil tunnels and coalmines, it is typically 2:1.) Source: Lang and Bischoff (1982)2.06Ground ControlIn mining, the bolt length/bolt spacing ratio is acceptable between 1.2:1 and 1.5:1. Source: Z.T. Bieniawski (1992)2.07Ground ControlIn good ground, the length of a roof bolt can be one-third of the span. The length of a wall bolt can be one-fifth of the wall height. The pattern spacing may be obtained by dividing the rock bolt length by one and one-half. Source: Mike Gray (1999)2.08Ground ControlThe tension developed in a mechanical rock bolt is increased by approximately 40 Lbs. for each one foot-pound increment of torque applied to it. Source: Lewis and Clarke2.09Ground ControlA mechanical rock bolt installed at 30 degrees off the perpendicular may provide only 25% of the tension produced by a bolt equally torqued that is perpendicular to the rock face, unless a spherical washer is employed. Source: MAPAO2.10Ground ControlFor each foot of friction bolt (split-set) installed, there is 1 ton of anchorage. Source: MAPAO2.11Ground ControlThe shear strength (dowel strength) of a rock bolt may be assumed equal to one-half its tensile strength. Source: P. M. Dight2.12Ground ControlThe thickness of the beam (zone of uniform compression) in the back of a bolted heading is approximately equal to the rock bolt length minus the spacing between them. Source: T.A. Lang2.13Ground ControlHoles drilled for resin bolts should be ¼ inch larger in diameter than the bolt. If it is increased to 3/8 inch, the pull out load is not affected but the stiffness of the bolt/resin assembly is lowered by more than 80%, besides wasting money on unnecessary resin. Source: Dr. Pierre Choquette2.14Ground ControlHoles drilled for cement-grouted bolts should be ½ to 1 inch larger in diameter than the bolt. The larger gap is especially desired in weak ground to increase the bonding area. Source: Dr. Pierre Choquette2.15Ground ControlEvery 100° F rise in temperature decreases the set time of shotcrete by 1/3. Source: Baz-Dresch and Sherril2.16Mine DevelopmentPermanent underground excavations should be designed to be in a state of compression. A minimum safety factor (SF) of 2 is generally recommended for them. Source: Obert and Duval2.17Mine DevelopmentThe required height of a rock pentice to be used for shaft deepening is equal to the shaft width or diameter plus an allowance of five feet. Source: Jim Redpath2.18Stope Pillar and DesignA minimum SF of between 1.2 and 1.5 is typically employed for the design of rigid stope pillars in hard rock mines. Various Sources2.19Stope Pillar and DesignFor purposes of pillar design in hard rock, the uniaxial compressive strength obtained from core samples should be reduced by 20-25% to obtain a true value underground. The reduced value should be used when calculating pillar strength from formulas relating it to compressive strength, pillar height, and width (i.e. Obert Duval and Hedley formulas). Source: C. L. de Jongh2.20Stope Pillar and DesignThe compressive strength of a stope pillar is increased when later firmly confined by backfill because a triaxial condition is created in which s3 is increased 4 to 5 times (by Mohr’s strength theory). Source: Donald Coates2.21SubsidenceIn block caving mines, it is typical that the cave is vertical until sloughing is initiated after which the angle of draw may approach 70 degrees from the horizontal, particularly at the end of a block. Source: Fleshman and Dale2.22SubsidencePreliminary design of a block cave mine should assume a potential subsidence zone of 45-degrees from bottom of the lowest mining level. Although it is unlikely that actual subsidence will extend to this limit, there is a high probability that tension cracking will result in damage to underground structures (such as a shaft) developed within this zone. Source: Scott McIntosh2.23SubsidenceIn hard rock mines employing backfill, any subsidence that may occur is always vertical and nothing will promote side sloughing of the cave (even drill and blast). Source: Jack de la Vergne2.24Rockbursts75% of rockbursts occur within 45 minutes after blasting. Source: Swanson and Sines2.25RockburstsThe larger the rockburst, the more random the pattern in time of occurrence. Microseismic data from many areas shows that the smaller microseismic events tend to be concentrated at or just after blast time, on average (see above). However, the larger the event, the more random its time of occurrence. Source: Richard Brummer2.26RockburstsIn burst prone ground, top sills are advanced simultaneously in a chevron (‘V’) pattern. Outboard sills are advanced in the stress shadow of the leading sill with a lag distance of 24 feet. Source: Luc Beauchamp2.27RockburstsSeismic events may be the result of the reactivation of old faults by a new stress regime. By Mohr-Coulomb analysis, faults dipping at 30 degrees are the most susceptible; near vertical faults are the safest. Source: Asmis and Lee2.28RockburstsThere can be little doubt that it is possible to control violent rock behavior by means of preconditioning or de-stressing under appropriate circumstances. This technology, therefore, has the potential to be profitably harnessed for use in the mining of deeper orebodies, particularly hazardous situations such as highly stressed high grade remnants, or development into areas known to be prone to bursting. Source: Board, Blake & Brummer

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    Rule Number 3 -Rule of Thumb for Mining Methods

    3.01 Method SelectionA flatly dipping ore body may be mined using Blasthole when the height of ore exceeds 100 feet (30m); otherwise, it is mined Room and Pillar. Source: John Folinsbee
    3.02 InclinationOre will not run on a footwall inclined at less than 50 degrees from the horizontal. Source: Fred Nabb
    3.03InclinationEven a steeply dipping ore body may not be drawn clean of ore by gravity alone. A significant portion of the broken ore will inevitably remain (“hang”) on the footwall. If the dip is less than 60 degrees, footwall draw points will reduce, but not eliminate, this loss of ore. Source: Chen and Boshkov
    3.04Stope DevelopmentThe number of stopes developed should normally be such that the planned daily tonnage can be met with 60% to 80% of the stopes. The spare stopes are required in the event of an unexpected occurrence and may be required to maintain uniform grades of ore to the mill. This allowance may not be practical when shrinkage is applied to a sulfide ore body, due to oxidation. Source: Folinsbee and Nabb
    3.05Stope DevelopmentIn any mine employing backfill, there must be 35% more stoping units than is theoretically required to meet the daily call (planned daily tonnage). Source: Derrick May
    3.06Ore WidthBlasthole (longhole) Stoping may be employed for ore widths as narrow as 3m (10 feet). However, this narrow a width is only practical when there is an exceptionally good contact separation and a very uniform dip. Source: Clarke and Nabb
    3.07Ore WidthSequence problems are not likely in the case of a massive deposit to be caved if the horizontal axes are more than twice the proposed draw height. Source: Dennis Laubscher
    3.08Footwall DriftsFootwall drifts for blasthole mining should be offset from the ore by at least 15m (50 feet) in good ground. Deeper in the mine, the offset should be increased to 23m (75 feet) and for mining at great depth, it should be not less than 30m (100 feet). Source: Jack de la Vergne
    3.09DilutionA ton of ore left behind in a stope costs you twice as much as milling a ton of waste rock (from dilution). Source: Peter J. George

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    Post Rule of thumb no- 3 -Mine layout

    4.01 Pit LayoutThe overall slope (including berms, access roads, and haul roads) of large open pits in good ground will eventually approach the natural angle of repose of broken wall rock (i.e. 38 degrees), except for the last few cuts, which may be steeper. Source: Jack de la Vergne

    4.02 Pit LayoutWhen hard laterites are mined in an open pit, safe pit slopes may be steeper than calculated by conventional practice (as steep as 50 degrees between haul roads). Source: Companhia Vale do Rio Doce

    4.03Pit LayoutFor haul roads in general, 10% is the maximum safe sustained grade. For particular conditions found at larger operations, the grade has often been determined at 8%. It is usually safe to exceed the maximum sustained grade over a short distance. Source: USBM4.04
    Pit LayoutThe maximum safe grade over a short distance is generally accepted to be 15%. It may be 12% at larger operations. Source: Kaufman and Ault4.05Pit LayoutThe maximum safe operating speed on a downhill grade is decreased by 2 km/h for each 1% increase in gradient. Source: Jack de la Vergne4.06Pit LayoutEach lane of travel should be wide enough to provide clearance left and right of the widest haul truck in use equal to half the width of the vehicle. For single lane traffic (one-way), the travel portion of the haul road is twice the width of the design vehicle. For double lane (two-way), the width of roadway required is 3½ times the width of the widest vehicle. Source: Association of American State Highway Officials (AASHO)4.07Pit LayoutTo avoid a collision caused by spinout, the width of an open pit haul road should equal the width plus the length of the largest truck plus 15 feet safety distance. Source: Janet Flinn4.08Pit LayoutA crushed rock safety berm on a haulage road should be at least as high as the rolling radius of the vehicle tire. A boulder-faced berm should be of height approximately equal to the height of the tire of the haulage vehicle. Source: Kaufman and Ault4.09Crown PillarA crown pillar of ore beneath the open pit is usually left in place while underground mining proceeds. The height of the crown pillar in good ground is typically made equal to the maximum width of stopes to be mined immediately beneath. When the overburden is too deep, the ore body is not mined by open pit, but a crown pillar is left in place of height the same as if it were. If the outcrop of the ore body is badly weathered (“oxidized”) or the ore body is cut by major faults, under a body of water or a muskeg swamp - the height of the crown pillar is increased to account for the increased risk. Source: Ron Haflidson and others4.10Mine EntriesSmall sized deposits may be most economically served by ramp and truck haulage to a vertical depth of as much as 500m (1,600 feet). Source: Ernie Yuskiw4.11Mine EntriesA medium-sized deposit, say 4 million (short) tons, may be most economically served by ramp and truck haulage to a vertical depth of 250m (800 feet). Source: Ernie Yuskiw4.12Mine EntriesThe optimum “changeover” depth from ramp haulage to shaft hoisting is 350m (1,150 feet). Source: Northcote and Barnes4.13Mine EntriesIn good ground, at production rates less than one million tons per year, truck haulage on a decline (ramp) is a viable alternative to shaft hoisting to depths of at least 300m. Source: G.G. Northcote4.14Mine EntriesWestern Australia practice suggests a depth of 500m or more may be the appropriate transition depth from decline (ramp) haulage to shaft hoisting. Source: McCarthy and Livingstone 4.15Mine EntriesProduction rates at operating mines were found to range from 38% to 89% of the estimated truck fleet capacity. For a proposed operation, 70% is considered to be a reasonable factor for adjusting theoretical estimates to allow for operating constraints. Source: McCarthy and Livingstone4.16Mine EntriesShallow ore bodies mined at over 5,000 tpd are more economically served by belt conveyor transport in a decline entry than haul trucks in a ramp entry. Source: Al Fernie4.17Mine EntriesAs a rule, a belt conveyor operation is more economical than rail or truck transport when the conveying distance exceeds one kilometer (3,281 feet). Source: Heinz Altoff4.18ShaftsThe normal location of the production shaft is near the center of gravity of the shape (in plan view) of the ore body, but offset by 200 feet or more. Source: Alan O’Hara4.19ShaftsThe first lift for a near vertical ore body should be approximately 2,000 feet. If the ore body outcrops, the shaft will then be approximately 2,500 feet deep to allow for gravity feed and crown pillar. If the outcrop is or is planned to be open cut, the measurement should be made from the top of the crown pillar. If the ore body does not outcrop, the measurement is taken from its apex. Source: Ron Haflidson4.20ShaftsThe depth of shaft should allow access to 1,800 days mining of ore reserves. Source: Alan O’Hara4.21ShaftsFor a deep ore body, the production and ventilation shafts are sunk simultaneously and positioned within 100m or so of each other. Source: D.F.H. Graves4.22Underground LayoutFootwall drifts for blasthole mining should be offset from the ore by at least 15m (50 feet) in good ground. Deeper in the mine, the offset should be increased to 23m (75 feet) and for mining at great depth it should be not less than 30m (100 feet). Source: Jack de la Vergne4.23Underground LayoutOre passes should be spaced at intervals not exceeding 500 feet (and waste passes not more than 750 feet) along the footwall drift, when using LHD extraction. Source: Jack de la Vergne4.24Underground LayoutThe maximum economical tramming distance for a 5 cubic yard capacity LHD is 500 feet, for an 8 cubic yard LHD it is 800 feet. Source: Len Kitchener4.25Underground LayoutThe amount of pre-production stope development required to bring a mine into production is equal to that required for 125 days of mining. Source: Alan O’Hara

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    Rule Number 4 -Rule of Thumb for Enviromental

    Environmental Impact Statement The cost of an environmental impact statement (EIS) (including base line monitoring and specific previously performed studies) may cost approximately 2.5% of the total pre-production capital cost for a plain vanilla domestic mining project. The cost can increase by 2% for an undertaking that is politically or environmentally sensitive. In the latter case, the cost may increase further if proposals are challenged in the courts. Source: R.W. Corkery


    5.02 Site Layout If the mill (concentrator) is located close to the mine head, the environmental impact is reduced and so are the costs. Pumping tailings from the mill is cleaner, less disruptive to the terrain, and less expensive than to truck haul ore over a similar distance. When pumping water to the mill and hauling concentrate from the mill is considered, the argument is usually stronger. The rule is further reinforced in the case of an underground mine where a portion of the tailings is dedicated for paste fill or hydraulic fill. Source: Edgar Köster


    5.03 Site Layout The mine administration offices should be located as near as possible to the mine head to reduce the area of disturbance, improve communications, and reduce transit time. Source: Brian Calver


    5.04 Site Layout When a mine has a camp incorporated into its infrastructure, the campsite should be as close as practical to the mine to minimize the impact from service and utility lines, decrease the area of the footprint of disturbance, shorten travel time, and reduce costs. Source: George Greer


    5.05 Site Drainage and Spill Protection Drainage ditches to protect the mine plant should be designed to develop peak flow rates based on 100 year, 24 hour storm charts. Source: AASHO
    5.06 Site Drainage and Spill Protection Dykes around tank farms should be designed to hold 100% of the capacity of the largest tank + 10% of the capacity of the remaining tanks. Source: George Greer


    5.07 Water Supply If a drilled well is to be used for fire fighting without additional storage, it should demonstrate (by pumping test) a minimum capacity of 40 USGPM continuously for two hours during the driest period of the year. Various Sources
    5.08 Water Supply Chlorine should be added to water at a rate of approximately 2 mg/litre to render it safe to drink. Source: Ontario Ministry of Health and Welfare


    5.09 Dust Suppression Dust emissions emanating from the transport of ore will not remain airborne when the size of dust particle exceeds 10 m (ten microns). Source: Howard Goodfellow

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    Arrow Rule Number 5 -Rule of Thumb for mine maintenace

    The degree of maintenance enforcement at an operating mine should be just less than the point that disruptions to operations are at a level where additional maintenance costs equal the resulting profits from production. Source: David Chick

    28.02 General In a trackless mine operating round the clock, there should be 0.8 journeyman mechanic or electrician on the payroll for each major unit of mobile equipment in the underground fleet. Source: John Gilbert
    28.03 General Emergency repairs should not exceed 15% of the maintenance workload. Source: John Rushton

    28.04 General LHD units at a shallow mine with ramp entry should have a utilization of 5,000 - 6,000 hours per year. Source: Unknown
    28.05 General Captive LHD units should have a utilization of 3,500 - 4,500 hours per year. Source: Unknown

    28.06 General LHD units in production service should have a useful life of at least 12,000 hours, including one rebuild at 7,500 hours. A longer life can be presumed from LHD units at the high end of the market with on-board diagnostics. Source: John Gilbert

    28.07 General Underground haul trucks should have a useful life of 20,000 hours; more if they are electric (trolley system). Longer life may be presumed in the light of today’s improved onboard diagnostics and better management of equipment maintenance in general. Source: John Chadwick
    28.08 Service An efficient Maintenance Department should be able to install one dollar worth of parts and materials for less than one dollar of labor cost. Source: John Rushton

    28.09 Service A servicing accuracy of 10% is a reasonable goal. In other words, no unit of equipment should receive the 250-hour service at more than 275 hours. Source: Larry Widdifield

    28.10 Infrastructure With ramp entry, a satellite shop is required when the mean mining depth reaches 200m below surface. A second one is required at a vertical depth of 400m. Source: Jack de la Vergne
    28.11 Infrastructure With ramp and shaft entry, a main shop is required underground when the mean mining depth reaches 500m below surface. Source: Jack de la Vergne

    28.12 Infrastructure A main shop facility underground should have the capacity to handle 10% of the underground fleet. Source: Keith Vaananen
    28.13 Infrastructure Service shops for open pit mines should be designed with plenty of room between service bays for lay-down area. As a rule of thumb, the width of the lay-down between bays should be at least equal to the width of the box of a pit truck. Source: Cass Atkinson

    28.14 Infrastructure Surface shops should be designed with one maintenance bay for six haul trucks having a capacity of up to 150 tons. This ratio is 4:1 for larger trucks. The shops should also include one tire bay and two lube bays. Additional maintenance bays are required for service trucks (1:20) and support equipment (1:12). Source: Don Myntii

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    Arrow rule of thumb mineral economomics

    Metal PriceThe long-term average price of a common mineral commodity (the price best used for economic evaluation in a feasibility study) is 1.5 times the average cost of production, worldwide. Source: Sir Ronald Prain

    Pre-production Capital CostThe pre-production capital cost estimate (Capex) should include all construction and operating expenses until the mine has reached full production capacity or three months after reaching 50% of full capacity, whichever occurs first. This is the basic transition point between capital and operating costs. Source: John Halls

    expenditure includes all costs of construction and mine development until three months after the mine has reached 25% of its rated production capacity. Source: Jon Gill7.04Cash FlowThe total cash flow must be sufficient to repay the capital cost at least twice. Source: L. D. Smith

    Cash FlowProject loans should be repaid before half the known reserves are consumed. Source: G.R Castle

    Cash FlowIncremented cash flow projections should each be at least 150% of the loan repayment scheduled for the same period. Source: G.R. Castle

    Cash FlowThe operating cost should not exceed half the market value of minerals recovered. Source: Alan Provost7.08Net Present ValueThe discount factor employed to determine the NPV is often 10%; however, it should be Prime + 5%. Source: G.R. Castle

    Net Present ValueThe increment for risk may add 4% to 6% to the base opportunity cost of capital in the determination of a discount rate. Source: Bruce Cavender

    Net Present ValueThe value of the long-term, real (no inflation) interest rate is 2.5%. This value is supported by numerous references in the literature. Source: L.D. Smith

    Net Present ValueIn numerous conversations with managers of mining firms, I have found that 15% in real terms is the common discount rate used for decision purposes. Source: Herbert Drecshler

    (1980)Net Present ValueIn 1985, the discount rates of many
    mining companies raged from 14% to15%. Source: H. J.

    Net Present ValueThe true present value (market value) of a project determined for purposes of joint venture or outright purchase is equal to half the NPV typically calculated. Source: J. B.
    Redpath

    Rate of ReturnThe feasibility study for a hard rock mine should demonstrate an internal rate of return (IRR) of at least 20% – more during periods of high inflation. Source: J. B. Redpath

    Working CapitalWorking capital equals ten weeks operating cost plus cost of capital spares and parts. Source: Alan O’Hara

    Working CapitalWorking capital is typically ten weeks of operating cost plus the spare parts inventory. Source: METSInfo

    Closure Costs The salvage value of plant and equipment should pay for the mine closure costs. Source: Ron Haflidson7.18Closure Costs For purposes of cash flow, the cost of reclamation used to be equated with the salvage value of the mine plant, but this is no longer valid in industrialized nations. Source: Paul Bartos

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    محمد الطاهير
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    I NEED HELP,
    if i can recieve any books about economics and investment in exploration and production upstream and how to develop and produce a gas or oil field: number of appraisal wells, kind of surface equipment.....

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