Acidbase accounting (ABA): Tests conducted on rocks to determine if they will form acid or neutralise acid when exposed to oxygen and water. Acid-base accounting tests are typically conducted in a laboratory and usually measure maximum values of acid-forming potential or acid-neutralising potential. Rocks that form acid are commonly labelled PAF (potentially acid forming) and rocks that do not form acid are labelled NAF (non-acid forming).
Acid mine drainage (AMD): Acidity in ground and surface waters in mines, caused by chemical interactions with rocks, especially the mineral pyrite (iron sulphide). The process is the same as for ARD, but AMD arises because of human-induced changes to the rock mass, mainly by exposing fresh rocks to oxidation. Rocks at mine sites that are considered to be potentially acid forming (PAF) must be handled and disposed of in ways that minimise acid formation at the site. PAF waste rocks are commonly mixed with, or encapsulated in, non-acid-forming rocks (NAF).
Acid-neutralising capacity (ANC): Measure of the natural ability of a rock to neutralise acid in the environment. ANC is usually dominated by the mineral calcite (calcium carbonate).
Acid rock drainage (ARD): Natural acidity in ground and surface waters that is caused by chemical interaction with rocks. The process is the same as for AMD, but ARD is a natural phenomenon.
Acidity: Acidity in AMD or ARD is composed of mineral acidity (the hydroxide ion demand by cations of Fe, Al, Mn and others) and hydrogen ion acidity (measured as pH units).
Alluvial gold: Gold that has accumulated in sedimentary rocks, particularly river gravels and beach sands.
Alteration zone: Zone immediately adjacent to the ore zone, gold.
Baseline data: Environmental data used to establish baseline conditions for a proposed mining operation.
Benthic layer: Inorganic and organic material forming the streambed.
Biofilm: Community of algae, bacteria and fungi within a matrix of polysaccharides adhered to the surface of the stream-bed substrata.
Colloid: Particulate substance that is evenly distributed in a water sample and will not settle. Colloidal particles are typically 2200 nm in diameter and can pass through filters that are designed to separate dissolved components from particulate components.
Community: Group of plant and animal populations interacting within a given location.
Coagulation: Refers to the addition of chemicals to reduce the net electrical repulsive forces at particle surfaces, promoting consolidation of particles.
Contaminant: Any physical, chemical or biological substance that is introduced into the environment. Does not imply an effect. Usually refers to substances of anthropogenic origin.
Contaminated neutral drainage (CND): Mine waters that are not acid, but contain elevated levels of metals and therefore constitute an environmental issue. Arsenic is the most common contaminant in CND.
Ecosystem: The biological community and its abiotic environment.
Eh: The Eh of a water sample indicates the potential of the system to supply or absorb electrons during oxidation and reduction reactions. Eh is measured in milivolts and low values indicate that reduced chemical species are likely or that any oxidised chemical species present will be reduced. High Eh values indicate that oxidised species are most likely or that any reduced chemical species present will be oxidised.
EPT: A collection of specific aquatic invertebrate genera: Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies), typically considered to be sensitive to aquatic pollution.
Exploration: Prospecting, sampling, mapping, and other work involved in searching for ore. In some cases exploratory mining is conducted in which small-scale mining activities are carried out to study potential ore deposits
Deposit: Mineral deposit or ore deposit used to designate a natural occurrence of a useful mineral, or an ore, in sufficient extent and degree of concentration to invite exploitation.
Ecosystem: A dynamic complex of plant, animals and microorganism communities and their non-living environment interacting as a functional unit.
Flocculation: Refers to the addition of chemicals to join particles by bridging the spaces between suspended particles. Flocculants consist of polymer chemicals that adsorb suspended particles onto polymer segments.
Flow volume: Typically the unit of interest when assessing the potential impacts of mine drainage. It combines flow rate and volume and is expressed in units of m3/second.
Food web: Network of interactions resulting in the transfer of energy between species in a given location.
Geochemistry: The study of the chemical properties of rocks.
Geological formation: Group of rocks that are recognisable over a large area (typically > 10s of km2) and have similar characteristics such as age, composition, geological history and depositional environment.
Grazer: Organism primarily feeding on living algal tissue.
Hard rock gold: Gold in quartz veins and faults in basement rocks (greywacke, schist, granite, etc.).
Historical data: Environmental data that have been collected previously. This may include data from locations impacted by historical mine drainage or pristine sites.
HFO: Iron oxyhydroxides: A general name that includes a wide range of orange and brown iron oxide minerals (‘rust’), many of which are poorly crystalline. HFO forms naturally in the weathering environment, but can be enhanced by mining activity, and commonly accompanies AMD and CND. Also called ‘yellow boy’.
Hydrogeology: Physical and chemical processes of water movement in rocks.
Hydromining: Mining of coal using high pressure water jet to extract coal and gravity fluming to transport coal from the active mine face
Iron oxyhydroxide: See HFO.
Kinetic test: Analysis method for released dissolved components from rock where the testing regime monitors changes in rock chemistry with time. Typically kinetic tests expose rocks to simulated weathering processes and analysis is completed on leachate
Leaching: A chemical process for the extraction of valuable minerals from ore. Also, a natural process by which groundwaters dissolve minerals, thus leaving the rock with a smaller proportion of some of the minerals than it contained originally.
Macroinvertebrates: Organisms without backbones (e.g. worms, snails, insects and crustaceans) visible to the naked eye (generally > 500 μm in body length).
Maximum potential acidity: A theoretical measure of the total amount of acid that can be released from a rock after complete oxidation. This is largely based on the amount of pyrite (iron sulphide) present in the rock. See section 2.3.2.
Mine drainage: Collective term for groundwater, surface water runoff, and mine process water at a mine site.
Mine waste: Collective term for mine tailings, mine water and mine waste rocks.
Macroinvertebrate Community Index: A biotic index based on the relative abundance of specific aquatic macroinvertebrate genera.
Non-acid forming (NAF): See Acid mine drainage.
pH: A measure of the acidity or alkalinity of water, sediment or soil. The measure is based on the concentration of hydrogen ions and gives the negative logarithm of the hydrogen (H+) ion, corresponding to 10-7. A pH value of 7 is neutral. All values higher are considered alkaline, and all values lower are considered acidic.
Precipitation: The condensation of a solid from a solution
Ore: A natural mineral deposit in which at least one mineral occurs in sufficient concentrations to make mining the mineral economically feasible
Oxidation: A chemical reaction in which electrons are lost from an atom and the charge of the atom becomes more positive. Normally, oxidation involves the addition of atmospheric oxygen or water. Oxidation occurs concurrently with reduction.
Oxide minerals: A group of minerals whose fundamental unit is oxygen, O2-. The common cations in oxides include Cu2+, Mg2+, Al3+, Fe2+, Mn2+.
Oxides: See Oxide minerals.
Potentially acid forming (PAF): See Acid mine drainage.
QMCI: Quantitative Macroinvertebrate Community Index, a biotic index based on the relative abundance of specific aquatic macroinvertebrate genera.
Reactive transport modelling: Chemical modelling to predict the partitioning of dissolved, solid, gaseous and adsorbed phases in aqueous environments. Commonly reactive transport modelling involves mixing water from different sources with different chemical compositions to assess the physiochemical conditions and concentrations in the downstream environment.
Residence time: Length of time mine water spends in a passive treatment system.
Shredder: Organisms that primarily feed on coarse particles (> 1 mm) of dead or decaying vegetation including both leaves and wood.
SQMCI: Semi-Quantitative Macroinvertebrate Community Index, a biotic index based on the relative abundance of specific aquatic macroinvertebrate genera.
Tailings: Unwanted rock residues discharged from a mine processing site, commonly stored on a mine site behind a dam.
Taxon: Short for taxonomic unit, and is a common unit of identification among similar individuals. Often used when different types of organisms are identified to different levels (e.g. some to species, some to genus). Plural taxa.
Toxicity: The extent to which a substance, typically a contaminant, can cause damage to an exposed organism.
Sulphate mineral: A mineral characterised by the bonding of a sulphate anion with a metal such as calcium, lead or copper. Sulphates may or may not include water in their structure. Common examples include gypsum (CaSO4·2H2O).
Sulphates: See Sulphate mineral.
Sulphide mineral: A metallic mineral characterised by the covalent bonding of sulphur with a metal or semi-metal, such as iron, copper, lead, or zinc. An example of a common sulphide mineral is pyrite, which has the chemical formula FeS2. Sulphide minerals occur in a wide range of geological environments.
Sulphides: See Sulphide mineral.
Suspended solids: A solid substance present in water in an undissolved state, usually contributing directly to turbidity
Total Suspended Solids(TSS): The weight of material per volume of water and is reported in units of milligrams of suspended solids per litre of water (mg/L).
Toxicity: The inherent potential or capacity of a material to act on a group of selected organisms, under defined conditions. An aquatic toxicity test usually measures the proportion of organisms affected by their exposure to specific concentrations of chemical, effluent, elutriate, leachate, or receiving water.
Toxicity test: The means by which the toxicity of a chemical or other test material is determined. A toxicity test is used to measure the degree of response produced by exposure to a specific level of stimulus (or concentration of chemical).
Trophic level: Functional classification of organisms according to their feeding relationships. The basal level consists the primary food resource (plants, algae, detritus), followed by herbivores, predators, etc.
Turbidity: Measure of the amount of light scattered by suspended particles in a sample, typically reported in units of nephelometric turbidity units (NTUs).
Unconformity: The boundary between a group of older rocks and a group of younger rocks typically referred to in the context of alluvial gold. An unconformity normally represents a long time gap in the geological record, where uplift and erosion has occurred. Alluvial gold accumulates on unconformities during this erosion.
Waste rock: Rock which does not contain any minerals in sufficient concentration to be considered ore, but which must be removed in the mining process to provide access to the ore, but that has no immediate value itself and has to be stored on the mine site. Waste rock may be in situ, or excavated.
X-ray fluorescence: A common analytical method that determines the elemental composition of most substances to 1-10 ppm concentration level for most elements. XRF is mostly a laboratory-based analytical method, although field portable instruments are becoming more common. XRF does not analyse elements with lower atomic mass than fluorine.