Lacustrine deposit: 

Sediments deposited on the bottom of lakes.


Planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks.


An igneous rock, composed of dark minerals, that occurs in the form of dykes.


A residual soil developed in tropical countries, out of which the silica and aluminum hydroxides have been leached. May form orebodies of iron, nickel, bauxite and manganese.


A chute or trough for conveying pulp, water or powdered ore in a mill.


A general name for the molten rock ejected by volcanoes.


The general direction or slope of a device or ground surface.


The amount of material which must be mined for the slope of a pit wall to be at a safe angle, usually around 45 degrees in open pit mining.


Extractable by chemical solvents.


A chemical process in which a soluble metallic compound is extracted from ore by dissolving the metals in a solvent; also, a natural process by which ground waters dissolve minerals, thus leaving the rock with a smaller proportion of some of the minerals than it contained originally.


The bottom portion of gold-bearing channel gravels, particularly in buried placers.

Leaf Gold: 

Gold that forms in very this, flat leaf like pieces.


A horizontal layer of rock.


Generally used to describe a body of ore that is thick in the middle and tapers towards the ends.


A lens-shaped deposit having roughly the form of a double convex lens.


The person leasing or optioning a mining property.


A horizontal opening in a mine; levels are usually established at regular intervals, generally about 50 feet or more apart.


A humorous term for any rock meaning: "leave it right where you found it".


A soft, low-rank, brownish-black coal.


A bedded, sedimentary deposit consisting chiefly of calcium carbonate.


A brown, hydrous iron oxide.

Line cutting: 

Straight clearings through the bush to permit sightings for geophysical and other surveys.


Along the length of an object or area.


The act of placing visible markers indicating the boundaries of a claim.


A tract of land that has been surveyed and marked off.


A mineral deposit in solid rock.


The process of recording geological observations of drill core either on paper or on computer disk.

Longitudinal Retreat Mining: 

A method of mining an orebody beginning at one stope and gradually mining new stopes towards the central ore-handling system.

Long-hole open stope: 

A method of mining involving the drilling of holes up to 90 feet long into an ore body and then blasting a slice of rock which falls into an open space. The broken rock is extracted and the resulting open chamber is not filled with supporting material.

Long ton: 

2,240 lb avoirdupois (compared to a short ton, which is 2,000 lb).

Longwall mining: 

A method of mining coal in narrow vertical slices cut by mechanical means along long straight faces or walls.


The character of light reflected by minerals.


Visible to the unaided eye.


Igneous rocks composed mostly of dark, iron- and magnesium-rich minerals.


The molten material deep in the Earth, from which rocks are formed.

Magnetic gradient survey: 

A geophysical survey using a pair of magnetometers a fixed distance apart, to measure the difference in the magnetic field with height above the ground.

Magmatic Ore Deposit: 

Formed by differentiation of mineral in magma.

Magmatic segregation: 

An ore-forming process whereby valuable minerals are concentrated by settling out of a cooling magma.

Magnetic separation: 

A process in which a magnetically susceptible mineral is separated from gangue minerals by applying a strong magnetic field; ores of iron are commonly treated in this way.

Magnetic survey: 

A geophysical survey that measures the intensity of the Earth's magnetic field.

Magnetic susceptibility: 

A measure of the degree to which a rock is attracted to a magnet.


Magnetic iron ore, being a black iron oxide containing 72.4% iron when pure.


An instrument used to measure the magnetic attraction of underlying rocks.


Easily hammered and flattened when cold; refers to metals.


Wooden hammer for driving stakes.


A form of claim-staking practiced in Nova Scotia whereby claims are staked by drawing lines around the claim on claim maps at the provincial mines branch and an appropriate fee is paid.


A metamorphic rock derived from the re-crystallization of limestone by the application of heat and pressure.

Marginal deposit: 

An orebody of minimal profitability.


The rock or gangue material containing ore minerals.


A product of a smelter, containing metal and some sulfur which must be refined further to obtain pure metal.


Element (Hg) used in the recovery of gold by amalgamation.


Related to the openings in a sieve or screen.


Science of ore processing and metals.

Metallurgical coal: 

Coal used to make steel.


The process of extracting metals from their ores.

Metamorphic rocks: 

Rocks which have undergone a change in texture or composition as the result of heat and pressure.


The process by which the form or structure of rocks is changed by heat and pressure.

Meteoric water: 

Surface water that sinks into cracks and fissures.


An explosive mine gas composed of hydrogen and carbon.

Metric tonne: 

Equal to 1.102 standard short tons (U.S.).


Rock consisting of thin, alternating layers of granite and schist.


1) A plant in which ore is treated for the recovery of valuable metals, or the concentration of valuable minerals into a smaller volume for shipment to a smelter or refinery.

2) A piece of milling equipment consisting of a revolving drum, for the fine-grinding of ores as a preparation for treatment.

Millhead grade: 

The average grade of ore fed into a mill.


A treatment plant where valuable mineral is separated from the ore.


Ore which is not high-grade, but yet contains sufficient amounts of valuable metals to warrant the cost of recovery.

Milling ore: 

Ore that contains sufficient valuable mineral to be treated by milling process.


A measure of the voltage of an electric current, specifically, one-thousandth of a volt.

Mineable reserves: 

Ore reserves that are known to be extractable using a given mining plan.

Mine call factor: 

The ratio of the grade of material received at the mill to the grade of ore calculated by sampling in stopes.


A naturally occurring homogeneous substance having definite physical properties and chemical composition and, if formed under favorable conditions, a definite crystal form.

Mineral Resource: 

A mineral deposit or portion thereof, the tonnage and grade of which is not presently considered economic to mine and is not included in mineable reserves.

Mineralized material: 

An estimate of tonnage and grade of a mineral deposit with potential economic merit. Estimates of tonnage and grade are made on the basis of continuity, size and shape of mineralization. The extent of sampling required to quantify the estimate will vary with the level of geological understanding. Tonnage and grade estimates include provision for mining dilution.

Mineralized zone: 

Any mass of host rock in which minerals of potential commercial value occur.

Miner's inch: 

Water flow measure equal to 12.5 gallons per minute.

Mining claim: 

A portion of the public lands claimed for the valuable minerals occurring in those lands; obtaining mineral rights under mining law.


Smallest atomic combination that comprises a certain compound.


A very large nozzle which was used in hydraulic mining. It was aimed at the side of a mountain to wash the soil into sluice boxes where nuggets were trapped.


A single, large block of stone.


An object placed or erected to mark boundaries of a mining claim.

Mother lode: 

A gold-bearing district in California over 100 miles long. Also refers to very rich placer in ore deposits.


Ore or rock that has been broken by blasting.

Muck Pile: 

A large quantity of muck.

Muck sample: 

A representative piece of ore that is taken from a muck pile and then assayed to determine the grade of the pile.


A mucking machine; a piece of mining equipment which consists of a ore car equipped with a pneumatically operated shovel/bucket which pushes forward on rail while scooping up muck and placing it into the ore car.


Decayed vegetable matter and black soil forming swampy areas.