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abandoned mine; abandoned workings - (2) Excavations, either open, caved, or sealed, that are deserted and in which further mining is not intended.

abiotic - (4) environmental influences that arise form non-living entities, for example, climate; not biological, not produced by a living organism.

absorption - (4) the uptake of a gas by a solid or liquid, or a liquid by a solid. Absorption differs from adsorption in that the absorbed substance permeates the bulk of the absorbing substance. Also used to describe uptake by plants and animals.

acid/base accounting - (4) a series of chemical analyses and calculated values that provide a preliminary evaluation of the amounts, and relative balance, of the acid generation potential (AP or MPA) and acid neutralization potential (NP or ANC) of a sample. The calculated values are used to make preliminary projections about whether a sample will produce acid drainage. See also neutralization potential and acid potential

acid generation - (4) production of acidity. Various oxidation reactions produce acidity, including the decomposition of organic matter. The primary sources of acid generation in mine materials are sulfide oxidation and dissolution of residual acidic sulfide oxidation products. Generated acidity may be neutralized, released directly into solution or retained in the form of acid salts with the potential to dissolve at a later time. This term may be confused with the generation of acid drainage phenomena that require water drainage in addition to acid production . See ARD generation.

acid mine drainage (AMD); acid rock drainage (ARD) - (3) the exposure, usually as a result of mining, of sulfide bearing minerals to air and water, forming sulfuric acid. This acid dissolves metals such as lead, zinc, copper, arsenic, selenium, mercury, and cadmium into ground and surface water. Acid rock/mine drainage can poison ground and drinking water and destroy aquatic life and habitat. Commonly mined ore bodies that pose the risk of acid rock drainage include gold, silver, copper, iron, zinc and lead. (4) low pH drainage derived from materials with an insufficient capacity to neutralize the acidic products of sulfide and elemental sulfur oxidation and the dissolution products of acidic minerals and amorphous materials. ARD is produced when the neutralization potential is no longer capable of maintaining neutral pH conditions. In the context of mining, may be referred to as acid mine drainage (AMD).

acid mine water - (2) mine water which contains sulfuric acid, mainly due to oxidation of iron pyrite.

acid potential (AP) - (4) the maximum potential acid generation (MPA) from a sample. The calculation of AP (or MPA) is an integral part of acid/base accounting.

acidity - (4) a measure of the capacity of a solution to neutralize a strong base. Analytically determined by titration. A measure of excess hydrogen ions in solution and dissolved species (for example, trivalent aluminum and hydroxyaluminum complexes) capable of producing an excess. The acidity of a solution generally increases as its pH decreases. However, solutions with similar pH values may have very different acidities. See also alkalinity.

actinomycetes: Unicellular filamentous microorganisms that branch monopodially or more rarely dichotomously and form radiating colonies; mainly found in the soil, and cause of its characteristic odor.

acute toxicity - (3) any poisonous effect produced by single short-term exposure and resulting in severe biological harm or death. (4) lethal effects occuring over a short period of time. See also chronic toxicity.

adit - (2) a horizontal or nearly horizontal passage driven in rock from the surface for the working or dewatering of a mine.

adsorption - (4) process by which atoms, molecules or ions are retained on the surfaces of solids by chemical or physical binding. Not to be confused with absorption, which is the uptake of a gas by a solid or liquid, or a liquid by a solid.

aerobic - (4) in the presence of oxygen. See also anaerobic.

alkalinity - (4) a measure of the capacity of a solution to neutralize a strong acid. Analytically determined by titration. A measure of excess bicarbonate/carbonate and/or hydroxide ions in solution, or of a solid material's ability to produce an excess. The alkalinity of a solution generally decreases as its pH decreases. However, solutions with similar pH values may have very different alkalinities. See also acidity.

alluvial - (3) pertaining to material that is carried and deposited by running water.

alluvial fan - (3) a low, outspread, relatively flat to gently sloping mass of loose rock material deposited by a stream where it flows from a narrow mountain valley onto a plain or broad valley.

alluvium - (2) sediments deposited on land by streams and rivers. (3) any sediment deposited by flowing water, as in a river bed, floodplain, or delta.

aluminosilicates - (4) compounds containing silica, aluminum and oxygen as main constituents. See also silicates.

amorphous - (4) substances lacking detectable crystal structure or order. Usually used with reference to oxides or organic matter. See also mineral.

amalgam - (1) the combination of mercury (quicksilver) with one or another metals after milling, principally gold and silver.

amalgamation -(1) the process of bringing particles of free gold or silver into contact with mercury. The most common practice was to pass a slurry of crushed gold ore over large copper plates that had been coated with mercury. In the case of silver, a slurry mix of crushed silver ore was run through metal pans containing mercury. (2) the process by which mercury is alloyed with some other metal to produce an amalgam. Used at one time for the extraction of gold and silver from pulverized ores.

anadromous fish - (3) fish, such as salmon and steelhead, that hatch in fresh water, migrate to the ocean, mature there, and return to fresh water to reproduce.

anaerobic - (4) an environment without free oxygen. See also aerobic.

ANFO - (1) blasting agents comprised of a mixture of ammonium nitrate and fuel oil.

anhydrous - (4) to exist in a dehydrated state. See also hydration.

animal unit month (AUM) - (3) the amount of forage needed to sustain one cow, five sheep, or five goats for a month.

anoxic - (4) see anaerobic.

anoxic limestone drain - (4) a limestone bed designed to receive and neutralize acidic drainage with an oxygen-consuming or relatively impervious cover to minimize oxygen entry. The incorporation of anaerobic conditions to prevent iron precipitation and the resultant armoring or "blinding" of the limestone.

anthropogenic - (4) formed or influenced by man.

annual vegetation - (3) plants that complete their life cycles and die in 1 year or less.

aqua-regia - (4) a mixture of two concentrated acids, 1 part nitric (HNO3) to 3 parts hydrochloric (HCl) acids.

aquatic habitats - (3) habitats confined to streams, rivers, springs, lakes, ponds, reservoirs and other water bodies.

aquatic resources - (3) plants and animals that live within or are entirely dependent upon water to live; living resources of aquatic habitats (fish, invertebrates, ampibians); aquatic species.

aquifer - (3) a water-bearing bed or layer of permeable rock, sand, or gravel capable of yielding large amounts of water.

aspect - (3)(a) the visual first impression of vegetation at a particular time or seen from a specific point; (b) the predominant direction of the slope of the land.

assay - (4) to determine the size or composition (verb). The mass of a metal contained within a sample of rock (noun). Assay results are determined by chemical and analytical analyses and usually expressed in one of the following units: ppm, ppb, g/t, or oz/t.

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