Glossary of Mining Terms
- Acid Mine Drainage: Acidic run-off water from mine waste dumps and
mill tailings ponds containing sulfide minerals. Also refers to
ground water pumped to surface from mines.
- Adit: An opening driven horizontally into the side of a
mountain or hill for providing access to a mineral deposit.
- Alteration: Any physical or chemical change in a rock or
mineral subsequent to its formation. Milder and more localized than
- Anticline: An arch or fold in layers of rock shaped like
the crest of a wave.
- Assay: A chemical test performed on a sample of ores or
minerals to determine the amount of valuable metals contained.
- 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.
- Base Metal: Any non-precious metal (e.g. copper, lead,
zinc, nickel, etc.).
- Bedding: The arrangement of sedimentary rocks in layers.
- 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.
- Breccia: A rock in which angular fragments are surrounded
by a mass of fine-grained minerals.
- Bulk Mining: Any large-scale, mechanized method of mining
involving many thousands of tons of ore being brought to surface
- Channel Sample: A sample composed of pieces of vein or
mineral deposit that have been cut out a small trench or channel,
usually about ten cm wide and two cm deep.
- Chute: An opening, usually constructed of timber and equipped
with a gate, through which ore is drawn from a stope into mine cars.
- Commercially Mineable Ore Body: A mineral deposit that
contains ore reserves that may be mined economically.
- 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.
- Cone Crusher: A machine which crushes ore between a gyrating
cone or crushing head and an inverted, truncated cone known as a bowl.
- Concentrate: A fine, powdery product of the milling process
containing a high percentage of valuable metal.
- Commercially Mineable Ore Body: A sedimentary rock consisting of rounded,
water-worn pebble or boulders cemented into a solid mass.
- 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
- 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.
- Decline: An underground passageway connecting one or more
levels in a mine, providing adequate traction for heavy,
self-propelled equipment. Such underground openings are often
driven in an upward or downward spiral, much the same as a spiral
- Development: Work carried out for the purpose of opening up
a mineral deposit and making the actual ore extraction possible.
- Development Drilling: Drilling to establish accurate
estimates of mineral reserves.
- Diamond Drill: A rotary type of rock drill that cuts a core
of rock that is recovered in long cylindrical sections, two
centimeters 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
- Disseminated Ore: Ore carrying small particles of valuable
minerals spread more or less uniformly through the hose rock.
- Dore: Unparted gold and silver poured into molds when molten
to form buttons or bars. Further refining is necessary to separate
the gold and silver.
- Drift: A horizontal underground opening that follows along
the length of a vein or rock formation as opposed to a cross-cut
which crosses the rock formation.
- Drill-indicated Reserves: The size and quality of a potential
orebody as suggested by widely spaced drill holes; more work is
required before reserves can be classified as probable or proven.
- Due Diligence: The degree of care and caution required before
making a decision; loosely, a financial and technical investigation
to determine whether an investment is sound.
- 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.
- 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: Work involved in searching for ore, usually by
drilling or driving a drift.
- Face: The end of a drift, crosscut or stope in which work is
- Fissure: An extensive crack, break or fracture in rocks.
- Float: Pieces of rock that have been broken off and moved
from their original location by natural forces such as frost or
- Floatation: A milling process in which valuable mineral
particles are induced to become attached to bubbles and float, and
- Footwall: The rock on the underside of a vein or ore structure.
- 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
- Free Milling: Ores of gold or silver from which the precious
metals can be recovered by concentrating methods without resort to
pressure leaching or other chemical treatment.
- Galena: Lead sulfide, the most common ore mineral of lead.
- Geophysical Survey: Indirect methods of investigating the
subsurface geology using the applications of physics including
electric, gravimetric, magnetic, electromagnetic, seismic, and
- 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.
- Grade: The average assay of a ton of ore, reflecting metal
- Hangingwall: The rock on the upper side of a vein or ore
- Head Grade: The average grade of ore fed into a mill.
- Heap Leaching: A process involving the percolation of a
cyanide solution through crushed ore heaped on an impervious pad or
base to dissolve minerals or metals out of the ore.
- High Grade: Rich ore. As a verb, it refers to selective
mining of the best ore in a deposit.
- Host Rock: The rock surrounding an ore deposit.
- Hydro Metallurgy: The treatment of ore by wet processes
(e.g., leaching) resulting in the solution of a metal and its
- Intrusive: A body of igneous rock formed by the consolidation
of magma intruded into other rocks, in contrast to lavas, which are
extruded upon the surface.
- 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 rocks.
- Lens: Generally used to describe a body of ore that is thick
in the middle and tapers towards the ends.
- 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 meters or more apart.
- Limestone: A bedded, sedimentary deposit consisting chiefly
of calcium carbonate.
- Lode: A mineral deposit in solid rock.
- Metamorphic Rocks: Rocks which have undergone a change in
texture or composition as the result of heat and/or pressure.
- Mill: A processing plant that produces a concentrate of the
valuable minerals or metals contained in an ore. The concentrate
must then be treated in some other type of plant, such as a smelter,
to affect recovery of the pure metal.
- Milling Ore: Ore that contains sufficient valuable mineral to
be treated by the milling process.
- Mineable 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.
- Mineral Resource: A deposit or concentration of natural,
solid, inorganic or fossilized organic substance in such quantity
and at such grade or quality that extraction of the material at a
profit is currently or potentially possible.
- Mineralized Material or Deposit: A mineralized body which
has been delineated by appropriate drilling and/or underground
sampling to support a sufficient tonnage and average grade of
metal(s). Under SEC standards, such a deposit does not qualify as
a reserve until a comprehensive evaluation, based upon unit cost,
grade, recoveries, and other factors, conclude economic feasibility.
- Mineralization: The presence of economic minerals in a
specific area or geological formation.
- Muck: Ore or rock that has been broken by blasting.
- Native Metal: A metal occurring in nature in pure form,
uncombined with other elements.
- Net Profit Interest: A portion of the profit remaining after
all charges, including taxes and bookkeeping charges (such as
depreciation) have been deducted.
- Net Smelter Return: A share of the net revenues generated
from the sale of metal produced by a mine.
- Open Pit: A mine that is entirely on surface. Also referred
to as open-cut or open-cast mine.
- Ore: Material that can be mined and processed at a positive
- Ore Pass: Vertical or inclined passage for the downward
transfer of ore connecting a level with the hoisting shaft or a
- Orebody: A natural concentration of valuable material that
can be extracted and sold at a profit.
- 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.
- Oreshoot: The portion, or length, of a vein or other
structure, that carries sufficient valuable mineral to be extracted
- Oxidation: A chemical reaction caused by exposure to
oxygen that results in a change in the chemical composition of a
- Participating Interest: A company's interest in a mine,
which entitles it to a certain percentage of profits in return
for putting up an equal percentage of the capital cost of the
- Patent: The ultimate stage of holding a mineral claim in
the United States, after which no more assessment work is necessary
because all mineral rights have been earned.
- Patented Mining Claim: A parcel of land originally located
on federal lands as an unpatented mining claim under the General
Mining Law, the title of which has been conveyed from the federal
government to a private party pursuant to the patenting requirements
of the General Mining Law.
- Pillar: A block of solid ore or other rock left in place
to structurally support the shaft, walls or roof of a mine.
- Porphyry: Any igneous rock in which relatively large
crystals, called phenocrysts, are set in a fine- grained groundness.
- Precambrian Shield: The oldest, most stable regions of the
Earth's crust, the largest of which is the Canadian Shield.
- Prospect: A mining property, the value of which has not been
determined by exploration.
- Proven and Probable Mineral Reserves: Reserves that reflect
estimates of the quantities and grades of mineralized material at a
mine which the Company believes could be recovered and sold at
prices in excess of the cash cost of production. The estimates are
based largely on current costs and on projected prices and demand
for such mineralized material. Mineral reserves are stated
separately for each such mine, based upon factors relevant to each
mine. Proven and probable mineral reserves are based on calculations
of reserves provided by the operator of a property that have been
reviewed but not independently confirmed by the Company. Changes in
reserves represent general indicators of the results of efforts to
develop additional reserves as existing reserves are depleted
through production. Grades of ore fed to process may be different
from stated reserve grades because of variation in grades in areas
mined from time to time, mining dilution and other factors.
Reserves should not be interpreted as assurances of mine life or
of the profitability of current or future operations.
- Probable Reserves: Resources for which tonnage and grade
and/or quality are computed primarily from information similar to
that used for proven reserves, but the sites for inspection,
sampling and measurement are farther apart or are otherwise less
adequately spaced. The degree of assurance, although lower than
that for proven reserves, is high enough to assume continuity
between points of observation.
- Proven Reserves: Resources for which tonnage is computed from
dimensions revealed in outcrops, trenches, workings or drill holes
and for which the grade and/or quality is computed from the results
of detailed sampling. The sites for inspection, sampling and
measurement are spaced so closely and the geologic character is
so well defined that size, shape, depth and mineral content of
reserves are well established. The computed tonnage and grade are
judged to be accurate, within limits which are stated, and no such
limit is judged to be different from the computed tonnage or grade
by more than 20%.
- Raise: A vertical or inclined underground working that has
been excavated from the bottom upward.
Rake: The trend of an orebody along the direction of its
- Reclamation: The restoration of a site after mining or
exploration activity is completed.
- Recovery: The percentage of valuable metal in the ore that
is recovered by metallurgical treatment.
- 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.
- Reserves: That part of a mineral deposit which could be
economically and legally extracted or produced at the time of the
reserve determination. Reserves are customarily stated in terms of
"Ore" when dealing with metalliferous minerals.
- Resource: The calculated amount of material in a mineral
deposit, based on limited drill information.
Rockbolting: The act of supporting openings in rock with
steel bolts anchored in holes drilled especially for this purpose.
- 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
- 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 blast holes in open pit
- Royalty: An amount of money paid at regular intervals by the
lessee or operator of an exploration or mining property to the
owner of the ground. Generally based on a certain amount per ton or
a percentage of the total production or profits. Also, the fee paid
for the right to use a patented process.
- Sample: A small portion of rock or a mineral deposit, taken
so that the metal content can be determined by assaying.
- Secondary Enrichment: Enrichment of a vein or mineral deposit
by minerals that have been taken into solution from one part of the
vein or adjacent rocks and redeposited in another.
- Shaft: A vertical or steeply inclined excavation for the
purpose of opening and servicing a mine. It is usually equipped with
a hoist at the top which lowers and raises a conveyance for handling
personnel and materials.
- Shear or Shearing: The deformation of rocks by lateral
movement along numerous parallel planes, generally resulting from
pressure and producing such metamorphic structures as cleavage and
- Shrinkage Stoping: A stoping method which uses part of the
broken ore as a working platform and as support for the walls of the
- 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.)
- Skarn: Name for the metamorphic rocks surrounding an igneous
intrusive where it comes in contact with a limestone or dolomite
- Sphalerite: A zinc sulfide mineral; the most common ore
mineral of zinc.
- Step-out Drilling: Holes drilled to intersect a mineralized
horizon or structure along strike or down dip.
- Stockpile: Broken ore heaped on the surface, pending
treatment or shipment.
- Stope: An underground excavation from which ore has been
extracted either above or below mine level.
- Stratigraphy: Strictly, the description of bedded rock
sequences; used loosely, the sequence of bedded rocks in a
- Strike: The direction, or bearing from true north, of a vein
or rock formation measured 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 tons removed as waste relative
to the number of tons of ore removed from an open pit mine.
- Sublevel: A level or working horizon in a mine between main
- Sulfide: A compound of sulfur and some other element.
- Tailings: Material rejected from a mill after more 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.
- Trend: The direction, in the horizontal plane, or a linear
geological feature (for example, an ore zone), measured from true
- Troy Ounce: Unit of weight measurement used for all precious
metals. The familiar 16-ounce avoirdupois pound equals 14.583 Troy
- Unpatented Mining Claim: A parcel of property located on
federal lands pursuant to the General Mining Law and the
requirements of the state in which the unpatented claim is located,
the paramount title of which remains with the federal government.
The holder of a valid, unpatented lode mining claim is granted
certain rights including the right to explore and mine such claim
under the General Mining Law.
- Vein: A mineralized zone having a more or less regular
development in length, width and depth which clearly separates it
from neighboring rock.
- Volcano Genic: A term used to describe the volcanic origin of
- Vug: A small cavity in a rock, frequently lined with
well-formed crystals. Amethyst commonly forms in these cavities.
- Wall Rocks: Rock units on either side of an orebody. The
hanging-wall and footwall rocks of an orebody.
- Waste: Barren rock in a mine, or mineralized material that
is too low in grade to be mined and milled at a profit.
- Winze: An internal shaft.
- Zone of Oxidation: The portion of an orebody that has been
oxidized, usually in the upper portion of the ore zone.