Definitions

All injury frequency rate
Total number of injuries and fatalities per million hours worked.
All-in sustaining costs
Production costs plus all costs relating to sustaining current production and sustaining capital expenditure.
Back-fill
Waste material sourced from tailings or waste rock packed into the back of a stope with a form of cement to support the stope’s hangingwall.
Bunton
Metal (or historically, wooden) strut in a shaft used for supporting the sides of a shaft on which shaft equipment is fixed.
Carbon in Leach (CIL)
Process similar to CIP except that ore slurries are not leached with cyanide prior to carbon loading, instead leaching and carbon loading occurs simultaneously.
Carbon in Pulp (CIP)
Alternative to cyanidation process, in which gold occludes on the surface of fine carbon particles and from which gold can be recovered.
Carbon In Solution (CIS)
Process similar to CIP except that gold, which has been leached by cyanide into solution, is separated by the process of filtration.
Cleaning
Process of removing broken rock from a mine.
Comminution
Breaking, crushing or grinding of ore by mechanical means to make gold available for treatment.
Conglomerate
Coarse-grained classic sedimentary rock.
Cross-cut
Tunnel developed off a drive leading to which intersects a reef or stope.
Cut and fill
Method of underground mining in which a stope is excavated and refilled with waste/ tailings.
Cut-off grade
Minimum grade at which a unit of ore will be mined to achieve desired economic outcome.
Cyanidation
Treating finely ground rock with cyanide solution that dissolves gold.
Cyanide code
International management code for manufacture, transport and use of cyanide in producing gold. Aims to promote responsible management of cyanide used in gold mining.
Cyanide leaching
Extraction of precious metal from ore by its dissolution in a cyanide solution.
Decline
Shaft, developed from surface or underground at a shallow gradient to allow direct access to a deeper orebody.
Depletion
Decrease in quantity of ore in a deposit resulting from extraction or production.
Development
Horizontal or inclined excavations allowing access to stopes or a mine’s workings.
Development end
End of a drive, cross-cut or raise, currently being extended.
Dilution
Mixing of waste rock with ore, resulting in a decrease in overall grade.
Dissolution
Process whereby a metal is dissolved and becomes amenable to separation from gangue material.
Doré
Impure alloy of gold and silver produced at a mine to be refined to a higher purity.
Drive
Horizontal tunnel running from the shaft at different levels to give people and equipment access to their working places.
Electro-winning
Process of removing gold from solution by action of electric currents.
Elution
Removal of gold from activated carbon.
Fabricated gold
Gold on which work has been performed to turn it into a product, i.e. jewellery.
Fatal injury frequency rate
Number of work-related fatalities per million hours worked.
Feasibility study
Comprehensive technical and economic study of selected development option for a mineral project. Results of study may serve as basis for a final decision to proceed with project.
Flotation
Process whereby certain chemicals are added to material fed to leach circuit in order to float desired minerals to produce a concentrate of mineral to be processed.
Footwall
Underlying rock or side of a fault, orebody or stope which remains following excavation of reef or waste during mining or development and forms the “floor” of the excavated area.
Gangue
Commercially valueless material remaining after ore extraction from rock.
Gold beneficiation
Process of adding value to gold products by transforming gold bullion into fabricated gold products.
Grade
Amount of gold contained in a fixed amount of reef, generally measured in grammes of gold per tonne.
Greenfield
Potential mining site of unknown quality.
Grinding
Reducing rock to consistency of fine sand by crushing and abrading in a rotating steel grinding mill.
Hangingwall
Overlying rock which remains following excavation of reef or waste during mining or development and forms the “roof” of the excavated area.
Head grade
Grade of ore as delivered to the metallurgical plant.
In situ
Within unbroken rock or still in the ground.
Incline
Similar to a decline except an incline is constructed excavated from the bottom up.
Indicated mineral resource
Part of a mineral resource for which tonnage, grade and mineral content can be estimated with a reasonable level of confidence.
Inferred mineral resource
Part of a mineral resource for which tonnage, grade and mineral content can be estimated with a low level of confidence.
Kibble
Large bucket in which ore and waste rock are hoisted to surface.
Kriging
Estimation technique used in the evaluation of ore reserves.
Leaching
Dissolution of gold from crushed and milled material, including reclaimed slime, for absorption and concentration onto activated carbon.
Level
Workings or tunnels of an underground mine which are on the same horizontal plane.
Life of Mine (LoM)
Remaining years of production, based on production rates and ore reserves.
Longhole sub-level caving
Process for removing ore in which relatively thin blocks of ore are caused to cave in by successively undermining small panels of ore.
Lost time injury frequency rate
Number of lost time injuries per million hours.
Mat pack
Support made by layering wooden mats on top of each other to support the hanging wall.
Milling/mill
Comminution of ore, although the term has come to cover broad range of machinery inside the treatment plant where gold is separated from the ore.
Mine call factor
Ratio, expressed as a percentage, of the specific product recovered at the mill (plus residue) to the specific product contained in an ore body.
Mineable
Portion of a mineralised deposit for which extraction is technically and economically feasible.
Mineral reserves
Part of mineralised material which at the time of the reserve determination could be economically and legally extracted or produced.
Mineral resources
Concentration or occurrence of solid material in such form, grade and quantity that there are reasonable prospects for eventual economic extraction.
Mineralisation
Presence of a target mineral in a mass of host rock.
Mineralised material
Mineralised body that has been delineated by appropriately spaced drilling and/or underground sampling to support sufficient tonnage and average grade of metals to warrant further exploration.
Modifying factors
Considerations used to convert Mineral Resources to Ore Reserves. These include, but are not restricted to, mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social and governmental factors.
Open pit/Opencast/Open cut
Mining in which ore is extracted from a pit.
Ore
Mixture of material containing minerals from which at least one of the minerals can be mined and processed at an economic profit.
Ore grade
Average amount of gold contained in a ton of gold bearing ore expressed in ounces per ton.
Ore pass
Generally an excavation between two operating levels in a mine that allows gravitational movement of ore from a higher mining level to the level below from where it will be transported to the shaft and hoisted to surface.
Ore reserves
Part of a mineral deposit which could be economically and legally extracted or produced at the time of reserve determination.
Orebody
Well defined mass of material of sufficient mineral content to make extraction economically viable.
Ounce
Troy ounce (equal to 31.1035 grams) precious metals such as gold, silver or platinum.
Overburden
Soil and rock that must be removed in order to expose an ore deposit.
Pay limit
Breakeven grade at which the orebody can be mined without profit or loss, calculated using forecast gold price, working costs and recovery factors.
Precipitate
Solid product of chemical reaction by fluids such as zinc precipitation.
Productivity
Expression of labour productivity based on ratio of ounces of gold produced, or some other such measure, per employee in mining operations.
Project capital
Capital expenditure to either bring a new operation into production; to materially increase production capacity; or to materially extend productive life of an asset.
Prospecting right
Permission to explore an area for minerals.
Pyrite
Brassy-coloured mineral of iron sulphide (compound of iron and sulpher).
Quartz
Mineral compound of silicon and oxygen.
Raise
Tunnel following the line (dip) of the reef connecting one working level to another.
Recovery grade
Actual grade of ore realised after mining and treatment process.
Reef
Gold-bearing orebody, normally a conglomerate band, that contains gold.
Refining
Final stage of metal production in which final impurities are removed from molten metal by introducing air and fluxes. Impurities are removed as gases or slag.
Rehabilitation
process of restoring mined land to a condition approximating its original state.
Remnant pillar mining
Removal of blocks of ground previously left behind for various reasons during normal course of mining.
Reserve
An amount of gold in situ calculated with a high level of confidence by measuring underground gold grades. Reserves are divided into three general categories:
  • Proven: Highest confidence category of reserve estimate based on results of underground sampling.
  • Probable: Stated with a lesser degree of confidence than that for proved reserves but of sufficient quality to serve as the on which to make a development decision.
  • Possible: Stated with a lesser degree of confidence than probable but used as an additional indication when deciding on a deposit’s development.
Resource
Estimated amount of tonnes, grades and gold in situ calculated from fewer measurements than those available for calculating reserves and, therefore stated with less confidence. Resources are divided into three general categories:
  • Inferred: part of a mineral resource for which tonnage, grade and mineral content can be estimated with a low level of confidence.
  • Indicated: economic mineral occurrences that have been sampled to a point where an estimate has been made, at a reasonable level of confidence.
  • Measured: resources that have undergone enough further sampling that a competent person has stated to be an acceptable estimate, at a high degree of confidence.
Rock burst
Event caused by seismicity.
Rock dump
Lower grade coarse material deposited on surface historically due to the inability to efficiently recover the contained gold.
Roof bolt
Steel rod inserted into a hole drilled into the hanging wall or (more rarely) the sidewall and locked into place to help secure the area.
Run of Mine (RoM)
Loose term to describe ore of average grade.
Sampling
Gathering, measuring and analysing ore samples from underground working places or from surface or underground exploratory drilling.
Sand dumps
Surface dumps of slightly coarser residual material than slimes. Most material from Witwatersrand’s surface sand and slimes facilities/dumps re-milled and re-treated to recover residual gold.
Scattered mining method
Conventional mining applied in a non-systematic configuration.
Seismic event
Sudden inelastic deformation within a given volume of rock that radiates detectable seismic energy.
Seismicity
Sudden movement within a given volume of rock that radiates detectable seismic waves.
Semi autogenous grinding (SAG mill)
Piece of machinery used to crush and grind ore which uses a mixture of steel balls and ore itself to achieve comminution.
Shaft
Vertical or inclined excavation from surface that allows access to a mine’s workings
  • Ventilation shaft - vertical or inclined shaft from surface equipped with fans that suck air that has passed through the workings from a mine.
  • Hoisting shaft - vertical shaft from surface in which rock, people and materials are lowered into a mine or raised from it.
  • Sub-vertical shaft - shaft excavated started underground (not connected to surface) and that allows access to deeper ore bodies, which cannot be accessed from a single drop surface shaft.
Sidewall
Rock adjacent to excavated the area which forms vertical wall of an excavation.
Slimes
Finer fraction of tailings discharged from a processing plant after the valuable minerals have been removed.
Slimes dams
Surface deposits of slimes or tailings.
Slurry
Fluid comprising fine solids suspended in solution (often water containing additives).
Smelting
Thermal processing whereby molten metal is liberated from beneficiated ore or concentrate with impurities separating as lighter slag.
Spot price
Current price of a metal for immediate delivery.
Stockpile
Store of unprocessed ore.
Stope
Space left by the extraction of ore (mining) in an underground mine. Commonly referred to as the area where mining operations take place.
Stoping
Process of mining/extracting ore in an underground mine.
Stripping (stripping ratio)
Process of removing overburden to mine ore.
Sulphide
Mineral characterised by the linkages of sulpher with a metal or semi-metal, such as pyrite (iron sulphide). Also a zone in which sulphide minerals occur.
Tailings
Finely ground rock from which valuable minerals have been extracted by milling.
Tailings dam or Tailings Storage Facility (TSF)
Dams or dumps created from tailings or slimes.
Tonnage
Quantities where ton or tonne is an appropriate unit of measure. Typically used to measure reserves of gold-bearing material in situ or quantities of ore and waste material mined, transported or milled.
Tonnes vs tons
Tonnes are metric tonnes – 1,000 kilograms. Tons can be long tons or short tons. A long ton is 2,240 pounds (lbs) and a short ton 2,000 lbs. Short tons are generally a term used by American miners, metric tonnes by others.
Total cash cost per ounce
Measure of average cost of producing an ounce of gold, calculated by dividing total cash costs in a period by total gold sold over the same period.
Total production cost per ounce
Measure of average cost of producing an ounce of gold, calculated by dividing total production costs in a period by total gold production over the same period. Total production costs represent total cash costs, plus amortisation, depreciation and rehabilitation costs.
Virgin rock temperature
Normal temperature of a rock face. The deeper one goes into the earth, the greater the temperature of the rocks.
Waste
Rock mined with an insufficient gold content to justify processing.
Waste rock
Non-mineralised rock and/or rock that generally cannot be mined economically that is hoisted to surface for disposal.
Wits basin
Witwatersrand Basin is an underground geological formation once forming the shore and floor of a prehistoric sea. Basin reaches the surface on the Witwatersrand – an area near present-day Johannesburg – and stretches in an arc of up to 400 kilometres from Beatrix in the Free State gold fields to that of Evander in Mpumalanga. The basin contains consists of a sedimentary succession of gold-bearing reefs.
Yield
Actual grade of ore realised after the mining and treatment process.
Zama Zamas
Informal miners who enter mine workings to dig gold on their own account or extract gold from surface sources illegally.