Acidic precipitation:  Snow and rain that have a low pH, caused by sulfur dioxide and nitric oxide gases from industrial activity released into the atmosphere.

Acidic rocks: 

Usually refers to an igneous rock carrying a high (greater than 65%) proportion of silica.

Acid mine drainage: 

Acidic run-off water from mine waste dumps and mill tailings ponds containing sulfide minerals. Also refers to ground water pumped to surface from mines. Such drainage often requires treatment to buffer acidity before it can be released into the natural environment.


An opening or tunnel driven horizontally into the side of a mountain or hill for providing access to a mineral deposit. Strictly speaking, an adit is open to the atmosphere at one end, a tunnel at both ends.

Aerial magnetometer: 

An instrument used to measure magnetic field strength from an airplane.


A breccia composed largely or entirely of fragments of volcanic rocks.


A method of concentrating valuable minerals based on their adhesion properties.


In metallurgy, the act or state of being stirred or shaken mechanically, some times accomplished by the introduction of compressed air.

Agitation leaching: 

Leaching of gold from the host rock by agitating the ground ore in a cyanide solution.

Airborne survey: 

A survey made from an air craft to obtain photographs, or measure magnetic properties, radioactivity, etc.


A compound of two or more metals.

Alluvial, alluvium: 

Relatively recent deposits of sedimentary material laid down in river beds, flood plains, lakes, or at the base of mountain slopes.

Alluvial deposits: 

Riverbed gravel deposits resulting from the weathering of rock formations.

Alluvial fan: 

Soil washed or drifted down from mountains forming a tapered fan-shaped slope out into the valley.
Alluvium:  The soil that forms the alluvial fan.

Alpha meter: 

An instrument used to measure positively charged particles emitted by radio active materials.

Alpha ray: 

A positively charged particle emitted by certain radioactive materials.


Any physical or chemical change in a rock or mineral subsequent to its formation. Milder and more localized than metamorphism.

Alteration (Skarn): 

A body of rock into which molten rock has intruded (see intrusive) and which has been altered by the accompanying thermal reactions. "Skarn" is a particular type of altered rock which in some areas contains commercially-recoverable amounts of metals.


An alloy or union of mercury with another metal; gold or other metal that has been coated with mercury by adhesion.
Amalgamation:  Removing precious metals from ores by use of mercury.
Amorphous:  A term applied to rocks or minerals that possess no definite crystal structure or form, such as amorphous carbon.
Analysis:  The determination of the contents in any substance.
ANFO:  Acronym for ammonium nitrate and fuel oil, a mixture used as a blasting agent in many mines.
Anhydrous:  Refers to compounds having no water in their composition.
Anneal:  Heating and cooling metals to make them harder and stronger.
Annual labor:  Yearly assessment work on unpatented mining claims.
Anode:  A rectangular plate of metal cast in a shape suitable for refining by the electrolytic process.
Anomaly:  Any departure from the norm which may indicate the presence of mineralization in the underlying bedrock. In geophysics and geochemistry, an area where the property being measured is significantly higher or lower than the larger, surrounding area.
Anthracite:  A hard, black coal containing a high percentage of fixed carbon and a low percentage of volatile matter.
Anticline:  An arch or fold in the layers of rock shaped like the crest of a wave, as opposed to a syncline, which is similar to the trough of a wave.
Apex:  The top or terminal edge of a vein on surface or its nearest point to the surface.
Appalachian Region:  The eastern geological region of Canada consisting of the Appalachian Mountains.
Apron:  The canvas or cloth part of a rocker used to catch and hold gold.
Argonauts:  Gold seekers.
Aqua Regia:  Acid mixture of 3 parts hydrochloric and 1 part nitric acid.
Aqueous:  Containing water or related to material deposited by water.
Aquifer  A rock formation or basin containing water.
Arborescent:  Minerals that branch in treelike forms.
Archean:  Refers to rocks of the Archean geological era, usually applied to the oldest Precambrian rocks.
Argentite:  A silver sulfide mineral.
Argentiferous:  Pertains to silver-bearing rocks.
Argillaceous:  Consisting of clays or having a clayey nature.
Arrastra:  Crude stone mill for grinding and amalgamating gold ores. Also called a drag mill.
Arsenical:  Pertaining to or containing arsenic.
Artesian:  An aquifer or water bearing zone where the piezometric surface (pressure level) is above ground surface.
Assay:  A chemical test performed on a sample of ores or minerals to determine the amount of valuable metals contained.
Assay foot (meter, inch, centimeter):  The assay value multiplied by the number of feet, meters, inches, centimeters across which the sample is taken.
Assay laboratory:  A laboratory in which the proportions of metal in ores or concentrates are determined using analytical techniques.
Assay map:  Plan view of an area indicating assay values and locations of all samples taken on the property.
Assay Value:  The value of an ore as determined by assay results; the amount and worth of metals or minerals in a sample.
Assay-ton:  Assaying equivalent ton, equal to 29.166 grams.
Assessment work:  The amount of work, specified by provincial law, that must be performed each year in order to retain legal control of mining claims.
Asshole inspector:  The person responsible for making sure that miners coming up from underground aren't trying to steal ore samples.

Atomic Weight: 

The relative weight of an atom of an element as compared to the most stable isotope of carbon (At. Wt. 12.01115).

Attrition:  Loss of material through friction and abrasion.
Auger:  A screw type bit to bring material to the surface along the outside of the drill itself.
Auriferous:  Refers to gold-bearing rocks, gravels and sands.
Autoclave system:  Oxidation process in which high temperatures and pressure are applied to convert refractory sulfide mineralization into amenable oxide ore.
Autogenous grinding:  The process of grinding ore in a rotating cylinder, using as a grinding medium large pieces or pebbles of the ore being ground, instead of conventional steel balls or rods.
Avoirdupois:  Common system of weights used in the U.S. and Britain.
Axis:  The centerline of a crystal, object or rotating shaft.