Mineral Processing Glossary

Mineral Processing Glossary

Metallurgical Content

 

A

ABC Assay Based Controls are changes made to regulatory set-points that are biased on the level or changes in the level of the valuable metal being recovered.
Activators Cause a particular mineral to float with a collector when it otherwise would not.
Adsorption The gathering of a gas, liquid, or dissolved substance on a surface in a condensed layer.
Aggregate A group of unit or parts associated with one another. For example, a particle connected to a bubble.
Agitator A device for shaking or stirring.
Air Lock The blockage of a conduit by an air pocket which prevents flow – the flow resumes when the inlet pressure is high enough to dislodge the air bubble.
Analog Output See manipulated variable.
Annulus A ring.
Apex The bottom opening of a cyclone through which the underflow leaves.
Assay The analysis of the ore to determine its chemical content.
Attrition Grinding Grinding by wearing away through rubbing and chipping.
Automatic Mode Controller operating mode in which the controller changes the manipulated variable to effect control.

B

Baffles Are used to help the mixing action by breaking up circular flow patterns.
Ball Mill A tumbling mill in which steel balls tumble onto ore particles to break them.
Bornite (Cu5FeS4) A brownish-bronze mineral which contains copper, iron and sulphur. Bornite is a source of copper.
Bull Gear Also called ring gear, the gear that encircles the tumbling mill and transmits the motion of the pinion gear to the mill. The mill rotates as the pinion gear meshes with the bull gear.
Bypass The fraction of fine particles entrained by water in the classifier underflow.

C

Calcite (CaCO3) A colorless or white mineral which is composed of calcium carbonate.
Calibrate To determine, check, or adjust the scale of a thermometer, gauge, or other measuring instrument.  This is usually done by comparison with a standard instrument.
Carbonate A compound which contains a carbonate group (CO3) composed of carbon and oxygen. In a carbonate mineral the carbonate is attached to a metal.
Cascade Control A control methodology where a series of controllers in which the output of one controller is the set point of the next.
Cascading The motion of the charge in a tumbling mill which occurs when the grinding media roll down from the top of the load to the toe of the load.
Cataracting The motion of the charge in a tumbling mill which occurs when the grinding media are ejected from the top of the load onto the toe of the load.
Cavitation The formation and subsequent collapse of bubbles in a liquid.
Centrifugal Force The force that pushes a rotating object outward.
Chalcocite (Cu2S) A black mineral which contains copper and sulphur. Chalcocite is a source of copper.
Chalcopyrite (CuFeS2) A brass-yellow mineral which contains copper, iron and sulphur. Chalcopyrite is an important source of copper.
Circuit A link of all flotation stages.
Circulating Load The quantity of material recycled in a closed circuit. The circulating load is calculated by dividing the flow of material in the recycle by the flow of material in the feed.
Classification The separation of a mixture containing particles of different sizes into a stream containing coarse particles and a stream containing fine particles.
Cleaners A stage in a flotation circuit that treats concentrates from previous stages.
Closed Circuit A grinding circuit in which the underflow from the classifier at the mill discharge returns to the mill while the overflow leaves the circuit. In a normal closed circuit, the feed enters the circuit through the mill. In a reversed closed circuit, the feed
CMC Carboxyl Methyl Cellulose is a depressant that adsorbs in preference to collectors and gives hydrophilic products.
Coagulate The change from a liquid form into a thickened mass.
Coalescence What happens when two or more bubbles join together to form a single large bubble.
Comminution The breaking of large particles into small particles. The most common comminution processes are crushing and grinding.
Concentrate The valuable product from a mineral processing plant.
Concentrator A plant where mineral processing takes place – also called a mill.
Conditioner A tank, usually agitated by an impeller, used to allow mineral particles to react with reagents.
Controlled Variable Variable that the controller tries to maintain at set point
Coriolis Meter A device that uses the bending force generated when a fluid changes direction, through a bend for example, to calculate mass flow.
Correlation A relationship between two things.
Covalent Bond A bond formed by sharing electrons.
Cut Size The particle size at which the classifier feed particles have an equal chance of going to the overflow or the underflow.
Cyclone A classifier which uses centrifugal force to separate a mixture containing particles of different sizes into a coarse stream and a fine stream.

D

DCS A Distributed Control System distributes the monitor and control duties among several devices.
Density The mass of a material divided by its volume.
Depressants Prevents flotation of a particular mineral which otherwise would not float.
Digging Shoes Pick up the grinding media and ore particles that settle at the bottom of the tower mill.
Dispersants Reagents that dispose the slimes which often agglomerate and cover the surfaces of larger particles, therefore preventing them from being recovered.
Drag Retarding force on a body resulting from the resistance to flow put up by the viscosity of the surrounding fluid.

E

Eh Pulp Potential.
Electrochemical Electron transfer from one substance to another.
Electrometallurgy The process of using electricity to extract the valuable metal from the concentrate – aluminum is extracted by electrometallurgy.
Electrons Revolve around the nucleus of an atom and have a negative charge.
Electrowinning A refining process which uses electricity – gold is refined by electro-winning.
Entrainment A way in which particles enter the froth by being carried in the water that accompanies each bubble in the film and the wake.
Extraction The removal of the valuable metal from the concentrate – the main extraction methods use heat, chemicals, or electricity.

F

Flotation A process which uses the fact that different minerals have different affinities for certain chemicals in order to separate the valuable minerals from the gangue. The chemicals loaded with minerals are removed from the slurry by air bubbles.
Froth Bubbles formed on or in a liquid.
Froth Freezing A froth too dry to move.
Fuzzy Logic Control Fuzzy Logic Control determines control action using rules that are based on loose description of the process, for example, “if the level is high then reduce the water flow somewhat”.

G

Galena (PbS) a bluish gray mineral with which contains lead and sulphur. Galena is a source of lead.
Gamma Gauge A device which uses a weak radioactive source to produce gamma rays to measure density (% solids).
Gangue The unwanted portion of an ore.
Gland Seal A device which consists of packing compressed in a stuffing box for preventing slurry leakage around the rotating shaft joint.
Grade The percentage of a metal in a product.
Grain A small lump of a given mineral. In a typical large ore particle, the grains of valuable minerals are distributed throughout the gangue minerals.
Graphite A soft, black form of carbon with a metallic luster, used for lead in pencils, for lubricating machinery, etc.
Grind Out Procedure in which the mill is run without any solids feed for a short period to time to get rid of slurry in the mill.
Grinding Media Solid bodies which tumble onto ore particles to break them into smaller particles. The most common grinding media are steel balls, steel rods, and large ore particles.

H

Hardness Term referring to the ability to withstand penetration and deformation.
Head Pressure The energy supplied by the pump to the slurry. The head pressure is the difference between the pump discharge pressure and the pump suction pressure.
Head Tank A tank situated higher than the equipment is feeds. Flow to the equipment is under the force of gravity.
High Intensity Conditioner A conditioner where a vigorous stirring action is used.
Hydraulic Gradient Slope or change of height required for flow.
Hydrocarbon Any of a class of compounds containing only hydrogen and carbon.
Hydrocyclone A cyclone whose feed is a slurry of water and particles. It is also called a wet cyclone.
Hydrogen Bonds Bonds that result from the polar nature of water.
Hydrometallurgy The process of using chemical solutions to extract the valuable metal from the concentrate – gold and silver are extracted by hydrometallurgy.
Hydrophilic Water loving. Hydrophilic surfaces prefer to be in contact with water.
Hydrophobic Water fearing. Hydrophobic surfaces prefer to be in contact with something other than water, air for example.
Impact Grinding Grinding by the violent shattering which results from striking the particles.

I

Impede To obstruct.
Impeller The rotating blade of a centrifugal pump or blower.
Inching Slowly turning the mill to a new position. This is normally performed when relining the mill.
Induction Time The time it takes a particle to penetrate the water film and reach the air in the bubble.
Interface The boundary between any two phases (solid, liquid or gas).
Interlocks A control methodology where equipment can be permitted to start, started or shutdown based on certain conditions.
Ion A neutral atom that has electrons added or removed from it.
Ionic Bond A bond formed by donating atoms.

K

Keying the Charge To hold the charge. Lifters key the charge, preventing slippage and allowing the charge to rise. In practice only the bottom layer (height of the lifter) of the charge is actually keyed.
Kinetics The description of the rate of change in a physical or chemical system.

L

Launder A trough conveying a slurry.
Leaching An extraction method which uses the fact that different minerals have different solubility in chemical solutions to extract the valuable metal from the concentrate – gold and silver are normally extracted by cyanide leaching.
Liberated Particle A particle composed mostly of a single mineral.
Liberation The fundamental step of mineral processing by which the valuable minerals are freed from the gangue mineral. Liberation takes place through size reduction.
Lifters Pieces that “key” the charge to promote the tumbling action.
Liners Pieces that protect the mill shell from wear.
Locked Particle A particle composed of several minerals.
Logarithm In mathematics, an exponent of the power to which a fixed number (usually 10) must be raised in order to produce a given number.

M

Manipulated Variable The variable that the controller changes.
Manual Mode Controller operating mode in which the manipulated variable is kept constant. The controller suspends control action.
Marcy Scale An apparatus used to measure the density of a slurry.
Massive Sulphide Rock or ore composed mainly of sulphide minerals, both valuable minerals and gangue.
Measured Variable See controlled variable.
Mesh Size The number of openings per linear inch in a screen.
MIBC Methylisobutylcarbinol. A widely used frother.
Micron A measurement unit for length. There are 10,000 microns per centimeter, and 25,400 microns per inch.
Middlings A mixture of partly liberated particles.
Mill Charge See mill load
Mill Load The contents of the mill composed of grinding media and slurry. The total mill load also includes mill shell, liners, etc. that increase the weight at the trunnions.
Mineral Any compound with a fixed chemical composition and fixed physical properties found in the crust of the earth.
Mineral Processing The process of concentrating the valuable minerals in the ore in preparation for the extraction of the valuable metal.
MSDS The material safety data sheet outlines the hazards and first aid measures for each chemical.
MV See measured variable.

N

Net Smelter Return The economic value of the concentrate after transportation, smelting, refining and penalty charges are applied.
Neutrons Found in the nucleus of an atom and have a neutral charge.
Niobium A rare, steel gray, metallic chemical element that resembles tantalum in chemical properties.

O

Open Circuit A grinding circuit in which the particles go through the mill once. An open circuit has no classifier at the mill discharge to control particle size.
Ore A mineral deposit that can be mined at a profit.
Overflow The undersize material that leaves a cyclone.
Overload Unstable condition where the amount of material in the mill or in the circulating load increases and is compounded by a reduction in grinding capacity.
Oxide A compound which contains oxygen (O). In an oxide mineral, the oxygen is attached to a metal.

P

Particle A single physical entity.
Partition Curve A plot which describes how the particles fed to a classifier are divided between the overflow and the underflow. A partition curve gives the percentage of feed particles that report to the underflow for each particle size.
Percent (%) Solids The percentage by weight of solids in a slurry (often called pulp or slurry density).
pH A symbol used to express acid or alkaline content.
PID Controller A common controller which compensates proportionally to the error (P – proportional), compensates for sustained errors (I – integral) and compensates for changes in error (D – derivative).
Pinion The gear connected to the mill motor which causes the mill to rotate as its teeth mesh with the teeth of the bull gear.
Polar Bond A special type of covalent bond produced where there is an uneven sharing of electrons.
Polarity The uneven sharing of electrons.
Polymetallic Containing several valuable metals.
Porphyry Deposit A deposit where the sulphides are distributed through out a non-sulphide gangue. Usually a low grade deposit.
Power Energy per unit of time.
Precipitate To separate (a substance) out from a solution as a solid.
Process Variable See controlled variable.
Product The valuable stream that leaves the circuit.
Promoter A collector normally used in conjunction with another collector.
Protons Found in the nucleus in an atom and have a positive charge.
Pulp See slurry.
Pump Box A vessel which provides the pump with surge capacity.
PV See process variable.
Pyrite (FeS2) a pale brass-yellow mineral which contains sulphur and iron. It is also known as fool’s gold.
Pyrometallurgy The process of using heat to extract the valuable metal from the concentrate – iron is extracted by pyro-metallurgy (smelting).
Pyrrhotite (FeS) A bronze-colored mineral which contains sulphur and iron.

Q

Quiescent Zone The region between the mixing zone and the froth zone.

R

Ratio The relationship in quantity, amount or size between two things. Usually calculated by dividing one value by the other.
Ratio Control A control methodology where the controller output is calculated so that a ratio with a measured variable is maintained.
Reagent A substance used for its chemical activity.
Reagents Substances used to produce a desired chemical reaction.
Recovery The percentage of the valuable metal present in the feed that reports to the concentrate.
Recycle The stream that returns to pass again in the equipment. For example, the cyclone underflow in a closed ball mill circuit or the cleaner scavenger concentrate returned to the regrind mill.
Refining The process of removing impurities from the metal after it has been extracted from the concentrate.
Regulatory Control Refers to the low-level control used to stabilize the process. An example of regulatory control is the simple control loop used to maintain tonnage at a fixed value.
Residence Time See retention time.
Retention Time The length of time a slurry spends in a vessel.
Roping The condition which occurs when the air core inside a cyclone collapses and the spiralling motion is almost lost. When roping occurs, the discharge has the appearance of a thick rope.
Rougher The first stage in a flotation circuit that treats the fresh circuit feed.
RTD A resistance thermal device is a way of measuring temperature.  It varies resistance proportional to the temperature.

S

Scavenger A stage in a flotation circuit that treats the tailings from previous stages.
Sedimentation The settling of solid particles as a result of either gravity or centrifugal action.
Separation The fundamental step of mineral processing by which the product from the size reduction step (liberation) is separated into a valuable mineral stream (concentrate) and a gangue stream (tailings).
Set Point Desired value that a controller attempts to maintain.
Settling The motion of a solid within a liquid created by a force such as gravity.
SG See Specific Gravity.
Sharpness of Separation A measure of classification efficiency. The sharpness of separation is related to the slope of the partition curve.
Sieve A laboratory screen used to separate particles according to their size.
Silicate A compound which contains silica (Si).
Slimes Very fine particles, usually undesirable.
Slurry A mixture of ore particles and water.
Slurry Density The percentage of solids by mass.
Smelting An extraction method which uses heat to recover the valuable metal – iron and copper are usually extracted by smelting.
Sparger Is used to inject gases, usually air into the pulp.
Specific Gravity The mass of a substance compared to the mass of an equal volume of water. It is calculated by dividing the density of the substance by the density of water.
Sphalerite (ZnS) a mineral which contains zinc and sulphur. Sphalerite is a source of zinc.
Sulphate Any salt of sulphuric acid.
Sulphide A compound which contains sulphur (S). In a sulphide mineral, the sulphur is attached to a metal.
Sump Can refer to a floor sump (a pit used to collect spilled water or slurry), or can refer to the pump box.
Supervisory Control Refers to the high-level control that does not directly manipulate the valves and motors in the plant.
Surface Tension The tension in the interface between two phases. For example, a high surface tension at the air/water interface of a bubble means that it will rupture easily, like a stretched piece of cloth.
Surging Large fluctuations such as in flow or current.
System Dynamics The behavior of a system during a period of change.

T

Tailings The rejected material from a concentrator.
Talc A soft, smooth silicate of magnesium.
Tangential Which follows along a straight line that touches a curve at one point only.
Thickening The process of removing water to increase the concentration or density.
Ton A measurement unit for mass. There are 2,000 pounds in one ton.
Tonne A measurement unit for mass. There are 1,000 kilograms in one tonne.
Torque A force causing rotation.
Tower Mill A vertical cylinder with a special screw or stirrer designed to move the grinding media. Grinding is achieved by the rubbing action of the media as it moves.
Trommel The rotating cylindrical screen at the mill discharge which rejects coarse objects.
Trunnion The point of entry and discharge for the tumbling mill. The trunnion bearings support the mill at either end and ease rotation.
Tumbling Mill A rotating horizontal cylinder partially filled with grinding media that tumble onto the ore to grind it.
Tungsten A heavy, steel-grey metallic chemical element having the highest melting point of any of the metals.

U

Ultrasonic Probes A level of measurement in flotation cells.
Underflow The oversize material that leaves a cyclone.

V

Velocity Speed.
Viscosity The resistance of a fluid to flow.
Vortex Finder The top opening of a cyclone through which the overflow leaves.

X

X-Ray Fluorescence A phenomenon where material bombarded by X-Rays emits X-Rays of its own at specific frequencies.

 

404 Basic Mineral Processing Terms

Common Crushing Industry Terms & Vocabulary