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Glossary

A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  
A
Acid mine drainage
Acidic run-off water from mine waste dumps and mill tailings ponds containing sulphide minerals.
 
Adit
An opening driven horizontally into the side of a mountain or hill for providing access to a mineral deposit.
 
Aeromagnetic survey
A geophysical survey using a magnetometer aboard, or towed behind, an aircraft. The survey is used to evaluate the prospectivity of the land for mineral potential.
 
Agglomerate
A breccia composed largely or entirely of fragments of volcanic rocks.
 
Airborne survey
A survey made from an aircraft to obtain photographs, or measure magnetic properties, radioactivity, etc.
 
Alteration
Any physical or chemical change in a rock or mineral subsequent to its formation. Milder and more localized than metamorphism.
 
Amorphous
A term applied to rocks or minerals that possess no definite crystal structure or form, such as amorphous carbon.
 
Anomaly
Any departure from the norm which may indicate the presence of mineralization in the underlying bedrock.
 
Assay
A chemical test performed on a sample of ores or minerals to determine the amount of valuable metals contained.
 
Assay foot (or metre, inch, centimetre)
The assay value multiplied by the number of feet, metres, inches, centimetres across which the sample is taken.
 
Assessment work
The amount of work, specified by mining law, that must be performed each year in order to retain legal control of mining claims.
 
Autogenous grinding
The process of grinding ore in a rotating cylinder using large pieces of the ore instead of conventional steel balls or rods.
 
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B
Backfill
Waste material used to fill the void created by mining an orebody.
 
Ball mill
A steel cylinder filled with steel balls into which crushed ore is fed. The ball mill is rotated, causing the balls to cascade and grind the ore.
 
Banded iron formation
A bedded deposit of iron minerals.
 
Basal till
Unsorted glacial debris at the base of the soil column where it comes into contact with the bedrock below.
 
Bio-leaching
A process for recovering metals from low-grade ores by dissolving them in solution, the dissolution being aided by bacterial action.
 
Blasthole
A drill hole in a mine that is filled with explosives in order to blast loose a quantity of rock.
 
Block caving
An inexpensive method of mining in which large blocks of ore are undercut, causing the ore to break or cave under its own weight.
 
Box hole
A short raise or opening driven above a drift for the purpose of drawing ore from a stope, or to permit access.
 
Breccia
A rock in which angular fragments are surrounded by a mass of fine-grained minerals.
 
Broken reserves
The ore in a mine which has been broken by blasting but which has not yet been transported to surface.
 
Bulk mining
Any large-scale, mechanized method of mining involving many thousands of tonnes of ore being brought to surface per day.
 
Bulk sample
A large sample of mineralized rock, frequently hundreds of tonnes, selected in such a manner as to be representative of the potential orebody being sampled. Used to determine metallurgical characteristics.
 
Byproduct
A secondary metal or mineral product recovered in the milling process.
 
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C
Cable bolt
A steel cable, capable of withstanding tens of tonnes, cemented into a drill hole to lend support in blocky ground.
 
Cage
The conveyance used to transport men and equipment between the surface and the mine levels.
 
Carbon-in-pulp
A method of recovering gold and silver from pregnant cyanide solutions by adsorbing the precious metals to granules of activated carbon, which are typically ground up coconut shells.
 
Cathode
A rectangular plate of metal, produced by electrolytic refining, which is melted into commercial shapes such as wirebars, billets, ingots, etc.
 
Chalcopyrite
A sulphide mineral of copper and iron; the most important ore mineral of copper.
 
Channel sample
A sample composed of pieces of vein or mineral deposit that have been cut out of a small trench or channel, usually about 10 cm wide and 2 cm deep.
 
Chip sample
A method of sampling a rock exposure whereby a regular series of small chips of rock is broken off along a line across the face.
 
Chute
An opening, usually constructed of timber and equipped with a gate, through which ore is drawn from a stope into mine cars.
 
Collar
The term applied to the timbering or concrete around the mouth of a shaft; also used to describe the top of a mill hole.
 
Complex ore
An ore containing a number of minerals of economic value. The term often implies that there are metallurgical difficulties in liberating and separating the valuable metals.
 
Concentrate
A fine, powdery product of the milling process containing a high percentage of valuable metal.
 
Concentrator
A milling plant that produces a concentrate of the valuable minerals or metals. Further treatment is required to recover the pure metal.
 
Cone crusher
A machine which crushes ore between a gyrating cone or crushing head and an inverted, truncated cone known as a bowl.
 
Contact
A geological term used to describe the line or plane along which two different rock formations meet.
 
Core
The long cylindrical piece of rock, about an inch in diameter, brought to surface by diamond drilling.
 
Crosscut
A horizontal opening driven from a shaft and (or near) right angles to the strike of a vein or other orebody.
 
Cut-and-fill
A method of stoping in which ore is removed in slices, or lifts, and then the excavation is filled with rock or other waste material (backfill), before the subsequent slice is extracted.
 
Cyanidation
A method of extracting exposed gold or silver grains from crushed or ground ore by dissolving it in a weak cyanide solution. May be carried out in tanks inside a mill or in heaps of ore out of doors.
 
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D
Deck
The area around the shaft collar where men and materials enter the cage to be lowered underground.
 
Development
Underground work carried out for the purpose of opening up a mineral deposit. Includes shaft sinking, crosscutting, drifting and raising.
 
Diabase
A common basic igneous rock usually occurring in dykes or sills.
 
Diamond drill
A rotary type of rock drill that cuts a core of rock that is recovered in long cylindrical sections, two cm or more in diameter.
 
Dilution (mining)
Rock that is, by necessity, removed along with the ore in the mining process, subsequently lowering the grade of the ore.
 
Dip
The angle at which a vein, structure or rock bed is inclined from the horizontal as measured at right angles to the strike.
 
Directional drilling
A method of drilling involving the use of stabilizers and wedges to direct the orientation of the hole.
 
Disseminated ore
Ore carrying small particles of valuable minerals spread more or less uniformly through the host rock.
 
Drawpoint
An underground opening at the bottom of a stope through which broken ore from the stope is extracted.
 
Drill-indicated reserves
The size and quality of a potential orebody as suggested by widely spaced drillholes; more work is required before reserves can be classified as probable or proven.
 
Dry
A building where the miner changes into working clothes.
 
Dump
A pile of broken rock or ore on surface.
 
Dyke
A long and relatively thin body of igneous rock that, while in the molten state, intruded a fissure in older rocks.
 
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E
Electrolysis
An electric current is passed through a solution containing dissolved metals, causing the metals to be deposited onto a cathode.
 
Electrolytic refining
The process of purifying metal ingots that are suspended as anodes in an electrolytic bath, alternated with refined sheets of the same metal which act as starters or cathodes.
 
Environmental impact study
A written report, compiled prior to a production decision, that examines the effects proposed mining activities will have on the natural surroundings.
 
Epigenetic
Orebodies formed by hydrothermal fluids and gases that were introduced into the host rocks from elsewhere, filling cavities in the host rock.
 
Epithermal deposit
A mineral deposit consisting of veins and replacement bodies, usually in volcanic or sedimentary rocks, containing precious metals or, more rarely, base metals.
 
Exploration
Prospecting, sampling, mapping, diamond drilling and other work involved in searching for ore.
 
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F
Face
The end of a drift, crosscut or stope in which work is taking place.
 
Fault
A break in the Earth's crust caused by tectonic forces which have moved the rock on one side with respect to the other.
 
Felsic
Term used to describe light-colored rocks containing feldspar, feldspathoids and silica.
 
Fine gold
Fineness is the proportion of pure gold or silver in jewelry or bullion expressed in parts per thousand. Thus, 925 fine gold indicates 925 parts out of 1,000, or 92.5% is pure gold.
 
Flowsheet
An illustration showing the sequence of operations, step by step, by which ore is treated in a milling, concentration or smelting process.
 
Flux
A chemical substance that reacts with gangue minerals to form slags, which are liquid at furnace temperature and low enough in density to float on the molten bath of metal or matte.
 
Fracture
A break in the rock, the opening of which allows mineral-bearing solutions to enter. A "cross-fracture" is a minor break extending at more-or-less right angles to the direction of the principal fractures.
 
Free milling
Ores of gold or silver from which the precious metals can be recovered by concentrating methods without resorting to pressure leaching or other chemical treatment.
 
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G
Gabbro
A dark, coarse-grained igneous rock.
 
Geology
The science concerned with the study of the rocks which compose the Earth.
 
Geophysical survey
A scientific method of prospecting that measures the physical properties of rock formations. Common properties investigated include magnetism, specific gravity, electrical conductivity and radioactivity.
 
Geophysics
The study of the physical properties of rocks and minerals.
 
Glory hole
An open pit from which ore is extracted, especially where broken ore is passed to underground workings before being hoisted.
 
Gneiss
A layered or banded crystalline metamorphic rock, the grains of which are aligned or elongated into a roughly parallel arrangement.
 
Grab sample
A sample from a rock outcrop that is assayed to determine if valuable elements are contained in the rock. A grab sample is not intended to be representative of the deposit, and usually the best-looking material is selected.
 
Granite
A coarse-grained intrusive igneous rock consisting of quartz, feldspar and mica.
 
Greenstone belt
An area underlain by metamorphosed volcanic and sedimentary rocks, usually in a continental shield.
 
Grizzly (or mantle)
A grating, usually constructed of steel rails, placed over the top of a chute or ore pass for the purpose of stopping large pieces of rock or ore that may hang up in the pass.
 
Gross value
The theoretical value of ore determined simply by applying the assay of metal or metals and the current market price. It must be used only with caution and severe qualification.
 
Gross value royalty
A share of gross revenue from the sale of minerals from a mine.
 
Grouting
The process of sealing off a water flow in rocks by forcing a thin slurry of cement or other chemicals into the crevices; usually done through a diamond drill hole.
 
Grubstake
Finances or supplies of food, etc., furnished to a prospector in return for an interest in any discoveries made.
 
Gyratory crusher
A machine that crushes ore between an eccentrically mounted crushing cone and a fixed crushing throat. Typically has a higher capacity than a jaw crusher.
 
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H
Hangingwall
The rock on the upper side of a vein or ore deposit.
 
Head grade
The average grade of ore fed into a mill.
 
Heap leaching
A process whereby valuable metals, usually gold and silver, are leached from a heap, or pad, of crushed ore by leaching solutions percolating down through the heap and collected from a sloping, impermeable liner below the pad.
 
High grade
Rich ore. As a verb, it refers to selective mining of the best ore in a deposit.
 
Hoist
The machine used for raising and lowering the cage or other conveyance in a shaft.
 
Hydrometallurgy
The treatment of ore by wet processes, such as leaching, resulting in the solution of a metal and its subsequent recovery.
 
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I
Igneous rocks
Rocks formed by the solidification of molten material from far below the earth's surface.
 
Induced polarization
A method of ground geophysical surveying employing an electrical current to determine indications of mineralization.
 
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J
Jaw crusher
A machine in which rock is broken by the action of steel plates.
 
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L
Lagging
Planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rock.
 
Leaching
A chemical process for the extraction of valuable minerals from ore; also, a natural process by which ground waters dissolve minerals, thus leaving the rock with a smaller proportion of some of the minerals than it contained originally.
 
Level
The horizontal openings on a working horizon in a mine; it is customary to work mines from a shaft, establishing levels at regular intervals, generally about 50 metres or more apart.
 
Line cutting
Straight clearings through the bush to permit sightings for geophysical and other surveys.
 
Lode
A mineral deposit in solid rock.
 
Logging
The process of recording geological observations of drill core either on paper or on computer disk.
 
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M
Mafic
Igneous rocks composed mostly of dark, iron- and magnesium-rich minerals.
 
Magnetic gradient survey
A geophysical survey using a pair of magnetometers a fixed distance apart, to measure the difference in the magnetic field with height above the ground.
 
Magnetic separation
A process in which a magnetically susceptible mineral is separated from gangue minerals by applying a strong magnetic field; ores of iron are commonly treated in this way.
 
Metamorphic rocks
Rocks which have undergone a change in texture or composition as the result of heat and/or pressure.
 
Mill
A plant in which ore is treated and metals are recovered or prepared for smelting; also a revolving drum used for the grinding of ores in preparation for treatment.
 
Milling ore
Ore that contains sufficient valuable mineral to be treated by milling process.
 
Minable reserves
Ore reserves that are known to be extractable using a given mining plan.
 
Mineral
A naturally occurring homogeneous substance having definite physical properties and chemical composition and, if formed under favorable conditions, a definite crystal form.
 
Muck sample
A representative piece of ore that is taken from a muck pile and then assayed to determine the grade of the pile.
 
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N
Native metal
A metal occurring in nature in pure form, uncombined with other elements.
 
Net smelter return
A share of the net revenues generated from the sale of metal produced by a mine.
 
Nugget
A small mass of precious metal, found free in nature.
 
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O
Ore pass
Vertical or inclined passage for the downward transfer of ore connecting a level with the hoisting shaft or a lower level.
 
Ore Reserves
The calculated tonnage and grade of mineralization which can be extracted profitably; classified as possible, probable and proven according to the level of confidence that can be placed in the data.
 
Orebody
A natural concentration of valuable material that can be extracted and sold at a profit.
 
Outcrop
An exposure of rock or mineral deposit that can be seen on surface, that is, not covered by soil or water.
 
Oxidation
A chemical reaction caused by exposure to oxygen that results in a change in the chemical composition of a mineral.
 
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P
Pegmatite
A coarse-grained, igneous rock, generally coarse, but irregular in texture, and similar to a granite in composition; usually occurs in dykes or veins and sometimes contains valuable minerals.
 
Phaneritic
A term used to describe the coarse-grained texture of some igneous rocks.
 
Pillar
A block of solid ore or other rock left in place to structurally support the shaft, walls or roof of a mine.
 
Placer
A deposit of sand and gravel containing valuable metals such as gold, tin or diamonds.
 
Plunge
The vertical angle a linear geological feature makes with the horizontal plane.
 
Porphyry copper
A deposit of disseminated copper minerals in or around a large body of intrusive rock.
 
Possible reserves
Valuable mineralization not sampled enough to accurately estimate its tonnage and grade, or even verify its existence. Also called "inferred reserves." Primary deposits: Valuable minerals deposited during the original period or periods of mineralization, as opposed to those deposited as a result of alteration or weathering.
 
Probable reserves
Valuable mineralization not sampled enough to accurately estimate the terms of tonnage and grade. Also called "indicated reserves." Proven reserves: Reserves that have been sampled extensively by closely spaced diamond drill holes and developed by underground workings in sufficient detail to render an accurate estimation of grade and tonnage. Also called "measured reserves." Pyrite: A yellow iron sulphide mineral, normally of little value. It is sometimes referred to as "fool's gold".
 
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Q
Quartz
Common rock-forming mineral consisting of silicon and oxygen.
 
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R
Raise
A vertical or inclined underground working that has been excavated from the bottom upward.
 
Recovery
The percentage of valuable metal in the ore that is recovered by metallurgical treatment.
 
Refractory ore
Ore that resists the action of chemical reagents in the normal treatment processes and which may require pressure leaching or other means to effect the full recovery of the valuable minerals.
 
Replacement ore
Ore formed by a process during which certain minerals have passed into solution and have been carried away, while valuable minerals from the solution have been deposited in the place of those removed.
 
Resource
The calculated amount of material in a mineral deposit, based on limited drill information.
 
Rhyolite
A fine-grained, extrusive igneous rock which has the same chemical composition as granite.
 
Rock mechanics
The study of the mechanical properties of rocks, which includes stress conditions around mine openings and the ability of rocks and underground structures to withstand these stresses.
 
Rockbolting
The act of supporting openings in rock with steel bolts anchored in holes drilled especially for this purpose.
 
Rockburst
A violent release of energy resulting in the sudden failure of walls or pillars in a mine, caused by the weight or pressure of the surrounding rocks.
 
Room-and-pillar mining
A method of mining flat-lying ore deposits in which the mined-out area, or rooms, are separated by pillars of approximately the same size.
 
Rotary drill
A machine that drills holes by rotating a rigid, tubular string of drill rods to which is attached a bit. Commonly used for drilling large-diameter blastholes in open-pit mines.
 
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S
Sampling
Selecting a fractional but representative part of a mineral deposit for analysis.
 
Sandstone
A sedimentary rock consisting of grains of sand cemented together.
 
Schist
A foliated metamorphic rock the grains of which have a roughly parallel arrangement; generally developed by shearing.
 
Sedimentary rocks
Secondary rocks formed from material derived from other rocks and laid down under water. Examples are limestone, shale and sandstone.
 
Seismic prospecting
A geophysical method of prospecting, utilizing knowledge of the speed of reflected sound waves in rock.
 
Semi-autogenous grinding (SAG)
A method of grinding rock into fine powder whereby the grinding media consist of larger chunks of rocks and steel balls.
 
Shaft
A vertical or inclined excavation in rock for the purpose of providing access to an orebody. Usually equipped with a hoist at the top, which lowers and raises a conveyance for handling workers and materials.
 
Shear or shearing
The deformation of rocks by lateral movement along innumerable parallel planes, generally resulting from pressure and producing such metamorphic structures as cleavage and schistosity.
 
Shear zone
A zone in which shearing has occurred on a large scale.
 
Sheave wheel
A large, grooved wheel in the top of a headframe over which the hoisting rope passes.
 
Siderite
Iron carbonate, which when pure, contains 48.2% iron; must be roasted to drive off carbon dioxide before it can be used in a blast furnace. Roasted product is called sinter.
 
Silica
Silicon dioxide. Quartz is a common example.
 
Slag
The vitreous mass separated from the fused metals in the smelting process.
 
Solvent extraction-electrowinning (SX-EW)
A metallurgical technique, so far applied only to copper ores, in which metal is dissolved from the rock by organic solvents and recovered from solution by electrolysis.
 
Sphalerite
A zinc sulphide mineral; the most common ore mineral of zinc.
 
Step-out drilling
Holes drilled to intersect a mineralization horizon or structure along strike or down dip.
 
Stockpile
Broken ore heaped on surface, pending treatment or shipment.
 
Stope
An excavation in a mine from which ore is, or has been, extracted.
 
Stratigraphy
Strictly, the description of bedded rock sequences; used loosely, the sequence of bedded rocks in a particular area.
 
Strike
The direction, or bearing from true north, of a vein or rock formation measure on a horizontal surface.
 
Stringer
A narrow vein or irregular filament of a mineral or minerals traversing a rock mass.
 
Stripping ratio
The ratio of tonnes removed as waste relative to the number of tonnes of ore removed from an open-pit mine.
 
Sublevel
A level or working horizon in a mine between main working levels.
 
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T
Tailings
Material rejected from a mill after most of the recoverable valuable minerals have been extracted.
 
Tailings pond
A low-lying depression used to confine tailings, the prime function of which is to allow enough time for heavy metals to settle out or for cyanide to be destroyed before water is discharged into the local watershed.
 
Thickener
A large, round tank used in milling operations to separate solids from liquids; clear fluid overflows from the tank and rock particles sink to the bottom.
 
Tonnes-per-vertical-metre
Common unit used to describe the amount of ore in a deposit; ore length is multiplied by the width and divided by the appropriate rock factor to give the amount of ore for each vertical metre of depth.
 
Trench
A long, narrow excavation dug through overburden, or blasted out of rock, to expose a vein or ore structure.
 
Tuff
Rock composed of fine volcanic ash.
 
Tunnel
A horizontal underground opening, open to the atmosphere at both ends.
 
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U
Uncut value
The actual assay value of a core sample as opposed to a cut value which has been reduced by some arbitrary formula.
 
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V
Vein
A fissure, fault or crack in a rock filled by minerals that have travelled upwards from some deep source.
 
Visible gold
Native gold which is discernible, in a hand specimen, to the unaided eye.
 
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W
Wall rocks
Rock units on either side of an orebody. The hanging wall and footwall rocks of an orebody.
 
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Z
Zone
An area of distinct mineralization.
 
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Home > Mines & Projects > Operating Mines > Pinos Altos > Geology & Mineralization
Mines & Projects

Geology & Mineralization

Pinos Altos lies in the Sierra Madre gold belt, on the northeast margin of the Ocampo Caldera, which hosts many epithermal gold and silver occurrences.

The property is underlain by volcanic and intrusive rocks disturbed by faulting. Its geological focus is a horst structure (an uplifted block of rocks) at least 10 kilometres long by 3 kilometres wide, defined by the Reyna de Plata Fault to the north and the Santo Niño Fault to the south.

Mineralization on the property tends to be in low-sulphidation quartz-calcite breccia vein systems and stockworks carrying gold and silver, which are associated with the Santo Niño and Reyna de Plata structures marking the main horst structure.

Deposits

The most significant mineralization found on the property consists of four zones hosted by the Santo Niño Fault – the El Apache, Oberon de Weber, Santo Niño and Cerro Colorado lenses. More than 90% of the current Pinos Altos mineral resource is located in the steeply dipping Santo Niño vein zone, which is up to 40 metres thick and 2.5 kilometres long. It has a vertical extent of more than 750 metres, and remains open to the west and at depth.

The San Eligio zone, about 500 metres northeast of the Santo Niño zone, is part of the main mine project and continues to show promise. It is open along strike and at depth.

There are several other promising zones that are associated with the horst feature in the northwest part of the property. The Creston Mascota deposit is 7 kilometres northwest of the Santo Niño deposit, and is similar to it but dips shallowly to the west. Creston Mascota is about 1,000 metres long and 4 to 30 metres thick.

The Sinter zone, 1,500 metres north-northeast of the Santo Niño zone, is part of the Reyna de Plata gold structure. The steeply dipping mineralization is 4 to 35 metres wide and almost 900 metres long, with over 350 metres of vertical depth. Sinter is being evaluated for its open pit mining and heap leach potential.

The recently discovered Cubiro mineralization is 2 kilometres west of Creston Mascota. Cubiro is a surface deposit that strikes northwest, has a steep dip and has been followed along strike for about 850 metres. Drilling has intersected significant gold and silver mineralization up to 30 metres wide. The Cubiro deposit remains open in all directions.

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