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Hardrock Mining Glossary


Acid mine drainage is the drainage that results from sulfide oxidation in rocks exposed to air and water.

Adits are horizontal tunnels dug for access to underground mines.

Aesthetics involve the general visual environment, including the overall scenery and unique topographical characteristics.


Beneficiation is the processing of ore to separate the target mineral from the waste rock.


Cut-off is the point where the value of the mineral changes from an ore deposit to waste or from waste to an ore deposit. The cut-off is dependent on a number of factors, including the cost of mining and metallurgical treatment, the percentage recovery of the metal from treatment, the value of the metal recovered, the cost of transport and marketing, taxes and royalties, and the costs of environmental remediation.

Cyanide is used as a pyrite depressant in base metal flotation. It has also been used for over a century for gold extraction. Cyanide exists in many forms, depending on the starting compound and environmental conditions. The most common cyanide compound used in mining is sodium cyanide (NaCN).


Erosion is the process by which soil particles are detached, suspended, and transported from their source of origin.


Floation is a common form of beneficiation. It is adaptable to small particals and commonly used to recover lead, copper, platinum, and zinc. In floatation, the addition of a reagent chemical to ore slurry causes the minerals to become less dense than the gangue and rise to the top of the tank.


Gangue materials are the less valuable materials normally associated with the more valuable ore deposits.

Gravity separation is a common form of beneficiaton that relies on large differences in density between the target metal (e.g., gold) and the materials in which it is found. It also reqires that target metal cannot be bound to the surrounding rock matrix.


Habitat is the environment in which an organism normally lives. The three basic types of habitats are aquatic habitats, terrestrial habitats, and wetlands.

Hardrock Mining is generally defined as the extraction of metals (e.g., copper, gold, iron, lead, magnesium, silver, uranium, zinc) and non-fuel minerals (e.g., asbestos, gypsum, phosphate rock, sulfur) by surface or underground mining methods.

Hydrology relates to the flow characteristics and patterns of surface water and groundwater, including springs, wetlands, brooks, streams, rivers, ponds, lakes, and aquifers.


Leaching is the process of extracting a soluble metallic compound from ore. It involves dissolving the ore with a suitable solvent, such as sufuric acid or sodium cyanide solution.


Mill tailings are the coarsely and finely ground waste portions of mined material remaining after beneficiation operations have removed the valuable constituents from the ore.

Mine Water consists of all water that collects in mine workings, both surface and underground, as a result of inflow from rain or surface water and groundwater seepage.


Open pit mining is the most common method of extraction and involves a concentated excavation. The size of an open pit mine can vary from a small and superficial site to a pit more than 1000 feet deep and several square miles in area.

Ore is the concentration of minerals that can be processed and marketed at a profit.

Ore deposit or ore body can be extracted for a profit that is dependent upon technolgical, economical, societal, legal, political, and geological factors.

Ore mineral is a geologic term that refers to a deposit of metals that can feasibly be extracted.

Overburdern (see
waste rock)


Pollution prevention (in terms of mining) is the maximum feasible reduction of the quantity and/or toxicity of all wastes generated at a mining operation.

Primary crushing is a step that occurs after the ore has been removed from the earth and before beneficiation. Primary crushing reduces ore from 2-4 feet boulders to rocks 8-10 inches in diameter.

Pyrite is iron sulfide (FeS2).


Sedimentation occurs when eroded particles are deposited at a different location than the source of origin.

Slurry is formed when water is added to finely ground ore. It is also a waste product of beneficiation that consists of water containing additives, dissolved metals, dissolved solvents, heap and leaching wastes, and other impurities. Typical slurries consist of 40 to 70 percent liquid and 30 to 60 percent solids.

Spent ore is the material remaining after leaching.

Strip mining is used to extract horizontal, near surface ore deposits (e.g., phosphate). Strip mining progresses linearly and yields long disturbances.

Subsidence is the surface impact of collapsing overlying strata into mined-out voids. Subsidence may manifest itself in the form of sinkholes or troughs.

Surface Mining is the most common form of hardrock mining in use today and consists of extracting the ore by digging. The costs of machines and maintenance for surface mining are low compared to those for underground mining.


Tailings (see
mill tailings)


Underground mining involves digging vertical shafts and horizontal tunnels, or adits, to recover ore deposits.


Waste is the material not containing enough of the target mineral to pay for the cost of future processing.

Waste rock or overburden consists of rock and target minerals in concentrations too low for economic recovery. It is removed from the earth along with the ore. Waste rock includes granular, broken rock that ranges from fine sand to large boulders, depending on the nature of the formation and mining methods employed.

The information contained on these pages is a general statement of policy. It does not establish or affect legal rights or obligations. It does not establish a binding norm and is not finally determinative of the issues addressed. Agency decisions in any particular case will be made by applying the law and regulations to the specific facts of the case.