Appendix G: Glossary of Mining Terms

Glossary of Mining Terms

[Adapted from A Dictionary of Mining Mineral and Related Terms. Bureau of Mines, U.S. Department of the Interior (1996) (unless otherwise noted). This dictionary is available online at: Published on CD-ROM in 1996.] 

Acid mine drainage (AMD): Toxic drainage that usually results from exposure of pyritic materials to air and water. The acid dissolves minerals in the rocks, further degrading the quality of the drainage water. 

Ad­ministratively complete application: a permit application "which the regulatory authority determines to contain information addressing each application require­ment of the regulatory program and to contain all information necessary to initiate processing and public review." 30 C.F.R. § 701.5.

Alluvial valley floor (AVF):The unconsolidated stream-laid deposits holding streams where water availability is sufficient for subirrigation or flood irrigation agricultural activities...." 30 U.S.C. § 1291(1)See 30 C.F.R. 701.5.

Approximate Original Contour (AOC): A key mandatory reclamation standard in SMCRA requiring that the surface configuration achieved by backfilling and grading of a mined area, including any terracing or access roads, closely resembles the general surface configuration of the land prior to mining and blends into and compliments the drainage pattern of the surrounding terrain. All highwalls and spoil piles must be eliminated.  30 U.S.C. § 1291(2).

Aquifer: A stratum or zone below the surface of the earth that is capable of producing water, as from a well.

Backfilling: The filling in again of a place from which the rock or ore has been removed.

Bench: The horizontal step or floor along which coal is quarried.

Box cut: The initial cut driven into the land, where no open side exists; this results in a highwall on both sides of the cut.  This term applies to cuts made into the side of a mountain (countour mining) as well as cuts into flat ground (area mining).

Broad form deed: A contract format historically used by coal operators to gain favorable terms of mineral rights for themselves. The contract commonly used to negotiate with uneducated landowners who did not understand the terms of the contract.

Bucket-wheel excavator (BWE): An excavating device that uses buckets around the periphery of a vertically-mounted wheel to scoop spoil material out of the ground and load it onto a conveyor belt.

Cessation Order (CO): An order from a state inspector to discontinue operation of a mine. This occurs when the state receives word that an operator is doing something that will effect public health or safety or when the operator refuses to fix a violation. See 30 C.F.R. 840.11.   

Clean Water Act (CWA): A body of law that seeks to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters. 33 U.S.C. 1251.

Clinker: (sometimes called "scoria") Material usually reddish in color, overlying a burned coal bed, and usually comprised of baked clay, shale, or sandstone which has weathered to gravel-sized pieces. Clinker is often used for road surfacing.  (there are two definitions going here: one is baked rock above burnt out coal, primarily in the West.  The other is a pre-cursor to cement, formed when the material is baked in the kiln.  One is natural, the other is synthetic, and the synthetic one is used for road surfacing.)  See

Coal preparation plant: A plant for the cleaning and sizing of the raw coal before it is loaded into railway cars or trucks. See also 30 CFR 701.5.

Coal mine waste: The material left over following the cleaning and sizing of coal at a preparation plant. 30 CFR 701.5.

Compaction: An increase in soil density caused by mechanical handling of soil. Excessive compaction inhibits plant growth. 30 CFR 701.5;

Continuous mining: Mining in which a continuous mining machine cuts or rips coal from the face and loads it onto conveyors or shuttle cars. This eliminates the need for shooting and drilling.

Cumulative hydrologic impacts (CHIA): By using the probable hydrological  consequences the permitee is then to provide the probable collective “impacts of all anticipated mining in the  area upon the hydrology of the area and particularly upon water  availability.” 30 U.S.C. 1257(b)(11).

Dip: The angle at which a bed, stratum, or vein is inclined from the horizontal.

Dragline: A mechanical excavating device that casts a very large rope-hung bucket a considerable distance from its base and drags it back toward itself along the ground with a second rope thereby collecting large quantities of spoil material. The material is then elevated and dumped on a spoil pile or into a pit. Draglines are among the largest pieces of mining equipment used by mine operators.

Effluent: Waste in the form of a liquid, solid, or gaseous product that is discharged or emerges from a process.

Environmental Assessment (EA):  A public document by a Federal agency that provides sufficient evidence and analysis to determine whether to prepare an environmental impact statement (EIS) or a finding of no significant impact (FONSI).  The EA should include brief discussions of each of the elements required in an EIS. See 40 CFR 1508.9.

Environmental Impact Statement (EIS)A detailed written statement by an agency as required by NEPA for all major Federal actions significantly affecting the quality of the human environment that specifies the environmental impacts of the proposed action, unavoidable adverse environmental effects if the plan is implemented, alternatives to the plan, and other related information. See 42 U.S.C. 4332(2)(C).

Ephemeral Stream:  A stream that flows only in response to a precipitation event.
Face: The solid surface of the unbroken portion of the coal bed at the advancing end of the working place.

Fill: Manmade deposits of natural earth materials (e.g., rock, soil, and gravel) and waste materials (e.g., tailings or spoil from dredging) that is used to fill an empty space, such as an old excavation site or chamber in a mine.

Freedom of Information Act (FOIA): Government Agencies are required by law upon request to share any documents, including electronic documents, with the public. The agency may charge reasonable fees in order to supply the information. However, the agency may deny a citizen’s request because the document falls within an exception (e.g.  trade secrets, national security, medical records, etc.). See 5 U.S.C. 522(b).

Front-end loader: A tractor loader with a digging bucket mounted at the front end. A front-end loader both digs and dumps from the front.

Gob: Waste coal, rock pyrites, slate or other unmerchantable material extracted during underground mining and deposited either underground or on the surface in gob piles.

Head-of-hollow fill: (see Valley fill)

Highwall: "The face of the exposed overburden and coal seam in an open cut of a surface coal mining activity or for entry to underground mining activities." 30 CFR 701.5.

"Hot": A term applied to a mine or part of a mine that generates methane in considerable

Hydrologic balance: The maintenance of the quality and quantity of surface and ground water within the mine permit area and the surrounding areas by preventing toxic contamination and dewatering. See 30 U.S.C. 1265(b)(10).

Impoundment: A reservoir in which slurry is collected and sediments settle to the bottom. 

Intermittent stream: A stream that flows in direct response to a precipitation event or only at certain times of the year but which is dry during much of the year.

Last-cut lake: A permanent impoundment created when an area mine operator leaves the last cut empty instead of depositing the box cut spoil in the last cut. 

Longwall mining: A system of mining on straight faces up to 400 yards in length. A power machine shaves the coal along the face over the entire length of a panel designated for mining. Self-advancing hydraulic lifts are used to hold the ceiling in place until mining is completed on a given panel. The lifts are then removed and the ground is permitted to subside. (add cite)

Mountaintop removal mining: A coal extraction technique in which entire mountaintops are removed and the underlying coal seam is mined using surface mining methods. 

Mulch: Material (usually organic) used to control erosion and retain soil moisture. 30 CFR 701.5.

National Environmental Policy Act (NEPA): A body of law designed to encourage “productive and enjoyable harmony between man and his environment; to promote efforts” that will prevent or eliminate harm to the environment and to understand the ecological systems and natural resources important to the nation. This act also established a Council on Environmental Quality. 42 U.S.C. 4321.

Notice of Violation (NOV): Issued lieu of a cessation order in order to inform an operator that a rule, law, or permit condition has been violated and to begin corrective action.  NOVs may result in monetary penalties or criminal prosecution.

OSM: The Office of Surface Mining Reclamation and Enforcement is a federal agency created by SMCRA to implement, oversee, and enforce the law. 30 U.S.C. § 1211.

Outcrop: Area where the coal seam is exposed on the surface of the land.

Overburden: Material of any nature, consolidated or unconsolidated, that lies on top of a deposit of useful materials, ores or coal, especially those deposits that are mined from the surface by open cuts.

Percolation: Refers to the downward movement of water in the ground.

Perennial Stream:  A stream or river with continuous flow in all or part of its bed all year round.

Performance Standards: Operators must comply with certain regulations that attempt to conserve coal resources and restore the land to its pre-mining or better condition. 

Permit area: The area of land approved in the permit application that will be used for mining purposes. This includes both mining itself and any activity connected to mining (e.g. loading coal for commerce). The area also includes land adjacent to the mine site which is incidental to mining activities (e.g. roads, dams, storage areas, etc.). See 30 C.F.R. 701.5; See also 30 C.F.R. 700.5.   

pH: A term to describe the acidity of a solution. A pH of 7 is neutral. Each whole number lower describes a solution ten times more acidic than the previous number. Higher whole numbers indicate a solution more basic by a factor of ten.

Planned subsidence: Subsidence that occurs when all of the coal is removed during underground miningBecause subsidence is inevitable in this situation, and because it occurs quickly fater mining is completed, the operator is able to plan for subsidence and reclaim that surface.  Planned subsidence is most common in conjunction with longwall mining.

Pre-blast survey: A inspection conducted prior to blasting by either the operator of the mine or by an independent inspector in order to determine the physical state of a property prior to blasting. This inspection allows both operators and citizens to identify damage caused by blasting.

Prime farmland: "Those lands which are defined by the Secretary of Agriculture in 7 CFR 657... and which have historically been used as cropland."

NOTE: The regulations at 7 C.F.R. § 657 provide for an inventory of all prime farmlands. This inventory must be published on a map of a specified scale by the Soil Conservation Service. Information from these maps should be available at your local SCS office. To locate the SCS office nearest you, visit the following website: Click on your state, then on your county, and the website will tell you the address and phone number of your local SCS office.  Also, the rules define "cropland" as "lands used for the production of adapted crops for harvest, alone or in rotation with grasses and legumes…" They further define the phrase "historically used for cropland" as (a) "lands that have been used for cropland for any 5 years out of the 10 years immediately preceding the acquisition... of the land for... mining..." or (b) "lands which the regulatory authority determines, on the basis of additional cropland history of the surrounding lands and lands under consideration,... is clearly cropland…" or (c) "lands that would likely have been used as cropland for 5 out of the last 10 years immediately preceding such acquisition...but for the…ownership or control of the land unrelated to the productivity of the land." See 30 CFR 701.5.

Probable hydrologic consequences (PHC): A survey of the “hydrologic regime, quantity and quality of water in surface and ground water systems including the dissolved  and suspended solids under seasonal flow conditions and the collection of sufficient data for the mine site and surrounding  areas” so that the cumulative effects of mining may be predicted.  30 U.S.C. 1257(b)(11).

Pyrite: Iron disulfide (FeS2). (Fool's gold.) Pyrite deposits frequently occur near coal seams. When the pyrite mixes with water and air, a chemical reaction takes place which produces sulfuric acid. This is a significant source of acid mine drainage.

Recharge capacity: The ability of the soils and underlying materials to allow precipitation and runoff to infiltrate and reach the zone of saturation or water table. 30 CFR § 701.5.

Red dog: Solid waste from mining or coal processing that has burned. Usually reddish in color and used for road surfacing.

Reference area: A land unit maintained under appropriate management for the purpose of measuring vegetation ground cover, productivity and plant species diversity that are produced naturally or by approved crop production methods. Reference areas must be representative of geology, soil, slope and vegetation in the permit area. 30 CFR § 701.5.

Refuse: Solid waste from a coal preparation plant.

Retreat mining: A method of underground mining in which the pillars are “robbed,” or removed, and the ground is allowed to subside as the miners move out toward the mine entrance. Also known as retreating system.    

Riprap: Large broken rocks or boulders, often placed along embankments and dam faces to control erosion.

Rob the pillars: The mining of coal pillars left to support the roof during development mining, often resulting in cave-ins.

Room-and-pillar: Method of mining where flat lying beds of coal are mined in rooms separated by pillars of undisturbed rock left for roof support.

Safety factor: "The ratio of the available shear strength to the developed shear stress or the ratio of the sum of the resisting forces to the sum of the loading or driving forces, as determined by accepted engineering practices." 30 CFR § 701.5. A static safety factor of one on a slope means that the slope is extremely vulnerable to slides because the forces holding the material up equal those trying to bring it down.

Scalped: The process by which surface vegetation is removed prior to mining.

Scarification: The loosening or stirring of the surface soil without turning it over. Scarification can help reduce erosion by making it easier for the soil to absorb water.

Scraper: A machine used to remove and replace topsoil and other soil materials during mining and reclamation. Scrapers can cause severe compaction of the soil.

Sedimentation ponds: ponds designed to hold polluted stream water in one place long enough for suspended solids such as soil particles to drop out of the water and settle on the bottom of the pond. See 30 C.F.R. 816.46(c).

Sink hole: A hole or depression in the surface of the ground, caused by underground excavations or erosion of vertical support. Sink holes can be as much as 15 feet deep.

Slurry: Liquid waste composed of fine rock particles and water that is produced when coal is washed.

Soil horizons: A layer of soil that is characteristically distinct from adjacent layers. For example it is made up of a different texture, structure, or color than the adjacent layer. Horizons are usually designated by numerals or capital letters (e.g. Horizon A and Horizon B).

Soil profile: A vertical section of soil that displays all of the soil’s layers. Layers are often called horizons.

Spoil: The overburden or non-ore material that has been removed to gain access to the mineral.

Strata: Beds or layers of rock that are visually separable from other layers.

Stream buffer zone rule: a federal regulation stating that land within 100 feet of a stream cannot be disturbed by mining unless the operator can prove it will not adversely affect the water quality and quantity of the stream.   

Stripping ratio: The unit amount of spoil or overburden that must be removed to gain access to a unit amount of coal, generally expressed in cubic yards of overburden to raw tons of coal.

Subjacent support: Support by the earth that lies underneath the land under consideration. Black’s Law Dictionary, Westlaw online version.

Subsidence: Surface collapse or depression caused by underground excavations.

Subsidence control plan: A permitting requirement for underground mines; the plan must identify structures and renewable resource lands above the mine and discuss methods to prevent or reduce damages from subsidence to those structures and lands.  It also must describe how the operator will monitor subsidence.  See 30 C.F.R. § 784.20.

Swell Factor: The tendency of soils and overburden on being removed from their natural, compacted beds to increase in volume due to an increase in the space between soil particles.

Thalwegs The line of greatest slope along the bottom of a valley. The thalweg thus marks the natural direction of a watercourse. 

Topsoil: The surface portion of the soil, sometimes called the A-horizon. Topsoil will generally range from 6 to 20 inches in depth.

Valley fill: A fill structure consisting of any material other than coal waste or other organic material that is placed in the upper most area of a valley that is steeper than 20 degrees.