Glossary

Acidic – a condition where the concentration of positively charged hydrogen ions is high, and the pH is less than 7.0. EPA

Adit - a horizontal opening excavated from the surface of the earth for the working of a mine MTDEQ

Alkalinity – a measure of the ability of a solution to absorb positively charged hydrogen ions without a significant change in pH. Alkaline solutions have a pH greater than 7.0. EPA

Aquifer - a water-bearing bed of porous rock, often sandstone

Backfill - mine waste or rock put back in the mine after removing the valuable minerals

Basic – a condition where the concentration of negatively charged hydrogen ions is high, ahd the pH is greater than 7.0. EPA

Comminution – crushing or grinding ore to make the minerals more accessible.

Concentration - the process of separating raw into valuable minerals and waste materials to make processing more efficient.

Gangue – waste material with no economic value

Groundwater - Subsurface water that fills available openings in rock or surface materials to the extent that they are considered water saturated. MTDEQ

Dissolved Oxygen – the amount of oxygen that is dissolved in a solution. D.O. is usually measured in parts per million. EPA

Diversion – drainage ditches or barriers used to keep surface water from coming in contact with mine tailings or waste piles

Effluent – the solution that flows out of a basin, pond, tank, wetland, ditch, pipe, or other containment. EPA

Extraction – the removal of ore for processing

Fluvial – of or relating to or happening in a river

Geomorphology - scientific study of the nature and history of the landforms on the surface of the Earth

Grouting – the use of cement or other materials to make a watertight seal around mine openings or fissures in rock

Highwall - the vertical wall consisting of the material being mined and the overlying rock and soil strata (overburden) of the mining site. MTDEQ

Impoundment - a closed basin, naturally formed or artificially built, which is dammed or excavated for the retention of water, sediment, or waste. MTDEQ

In perpetuity - forever

Leaching - the removal in solution of the more soluble minerals by percolating water or extracting a soluble metallic compound from an ore by selectively dissolving it in a suitable solvent, such as water, sulfuric acid, hydrochloric acid, cyanide, etc. MTDEQ

Lode – a layer of ore between layers of rock

Macroinvertebrate ­– an animal without a backbone usually in nymph or larval stage; aquatic insect

Mill - A mineral processing facility which is a building with machines for grinding and pulverizing ores and extracting metals or producing a product. MTDEQ

Mineral - any ore, rock,or substance (other than oil, gas, or uranium) that is taken from below the surface or from the surface of the earth for the purpose of milling, concentration, refinement, smelting, manurfacturing, or other subsequent use or processing or for stockpiling for future use, refinement, or smelting. MTDEQ

Neutralize – to cause a solution to move toward a pH reading of 7.0 through chemical or biological processes. EPA

Ore - a mineral or mineral aggregate which contains precious or useful metals and occurs in such quantity, grade and chemical combination as to make extraction commercially profitable. MTDEQ

Overburden - all of the earth and other materials that lie above a natural mineral deposit and the earth and other material after removal from their natural state in the process of mining. MTDEQ

Oxidation – a reaction in which a substance loses electrons.

pH - A symbol for the degree of acidity or alkalinity of a solution. pH values from 0 to 6 indicate acidity and from 8 to 14 indicate alkalinity. A solution with a pH of 7 is considered neutral. MTDEQ

Precipitate – the process of dissolved compounds becoming solidified. EPA

Placer mining - Placer mining involves any type of mining where raw minerals are depostied in sand or gravel on the surface or in a streambed

Pyrite - A lustrous yellow mineral which is a common iron sulphide occurring abundantly as native ore and serving principally as a source of sulfur in the formation of sulfuric acid in acid mine drainage. MTDEQ

Reclamation -

Remediation -

Restoration -

Repository – a pit excavated on relatively flat land which holds tailings, mine wastes, and other materials removed from a mine site

Riparian – the vegetation located on or near the banks of a river or stream

Sediment - Matter that settles to the bottom of a liquid; matter deposited by wind (sand, silt, dirt, etc.) MTDEQ

Settling pond – a permanent or semi-permanent structure such as a pit or impoundment that is filled with water and used to remove suspended silt and waste metals from mine drainage.

Shaft - A vertical or steeply inclined excavation penetrating the earth’s surface that is connected to a mine. MTDEQ

Slag - the waste product of the process of smelting. PADEP

Slope – horizontal distance over vertical distance; angle

Smelting - the chemical reduction of a metal from its ore and certain fluxes by melting at high temperatures. The non-metallic material floats on top of the heavier metallic constituents in the molten state and remains in that position when it cools and hardens. MTDEQ

Subsidence - The collapsing of overburden materials resulting from underground mining or associated underground excavations that cause depressions or holes on the surface and damage to structures. MTDEQ

Tailings - the refuse material resulting from washing, concentrating or treating ground ore that is discharged from a mill. MTDEQ

Tailings pond - a pond of water with a constraining wall or dam into which mill effluents are deposited. MTDEQ

Topsoil - the upper surface layer of soil, usually darker andricher than the subsoil, that is naturally present and necessary for the growth and regeneration of vegetation on the surface of the earth. MTDEQ

Vein – a layer of ore between layers of rock

Waste rock - the rock or mineral which must be removed from a mine to keep the mining scheme practical, but which has no value PADEP

Watershed – an area of land which drains toward a single channel. EPA