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GLOSSARY | |  | |
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The following is a glossary of commonly used mining and geological terms and phrases that may be of assistance.
Ag
The chemical symbol for silver.
Anomaly
An anomaly is a departure from the norm and is higher, lower or different to its general surroundings. An anomaly may indicate the presence of mineralisation in the underlying bedrock. Geochemical anomalies generated in drilling and soil sampling, and geophysical anomalies such as magnetic and induced polarization (IP) anomalies, are typical of the anomalies described in exploration.
Assay
A chemical test performed on a sample of ore, minerals or concentrate to determine its metal/mineral content. Precious metals are usually given in parts per million (ppm), ounces per short ton or grams per metric tonne, while base metals are given in percentage.
Au
The chemical symbol for gold.
Base Metals
Any non-precious metal eg copper, lead, nickel or zinc. Base metals are commonly used in industry alone rather than in alloys.
Breccia
A rock in which angular fragments are surrounded by a mass of fine-grained minerals. These fragments may be produced by volcanic explosion, faulting or sedimentary deposition.
Chalcocite
Chalcocite is a copper mineral that is common in oxide ores. It is one of the most profitable copper ores as it usually has a high copper content while the copper is relatively easy to separate from the sulfur.
Chalcopyrite
Is another copper mineral and is comprised of copper and iron. The widespread distribution of chalcopyrite make it the leading source of copper. Chalcopyrite is a common mineral and is found in almost all sulfide deposits.
Channel Sample
A sample composed of pieces of vein or mineral deposit that have been cut out of a small trench or channel. These are usually the first samples taken from an ore deposit that are of significance. Grab samples refer to samples of outcrop that are taken at the early stages of exploration, but they are not as significant as they may represent only a few highly concentrated samples based upon visual indications.
COMEX
The major trading venue for commodities in the USA. Equivalent in Europe is the London Metal Exchange (LME). COMEX trades all base and precious metals and numerous other commodities.
Concentrate
An intermediate product between ore and metal which contains a high proportion of metal and where most of the waste has been eliminated. After initial processing, concentrate is often shipped to a refinery to be further processed into metal.
Copper quote
Copper grades are generally quoted as a percentage eg 5.1% indicates that 5.1% of the quoted material contains copper.
Copper prices are quoted in either USc/pound (from COMEX) or in US$/tonne (on the LME).
Copper costs are typically quoted in USc/pound.
Crushing and Grinding
Mined ores have to be crushed and milled into a fine powder to liberate the economic mineral particles in a number of stages. The primary crushers are used for the initial phase after the ore is conveyed to stockpiles.
Conventional milling circuits take the coarse ore through secondary, and possibly tertiary, crushing which produces pebble-sized fine ore. The fine ore is then fed into a grinding circuit of rod and ball mills, which reduce the ore to fine powder. Water is added during the milling process.
Cu
The chemical symbol for copper.
Cut-off grade
The estimated lowest grade of mineralised material that can be economically extracted.
Decline
A sloping underground opening for machine access from level to level or from surface; also called a ramp.
Diamond drilling
Drilling method using a diamond bit to cut a cylindrical hole for taking core samples.
Disseminated
Refers to an ore deposit consisting of fine particles of ore mineral dispersed through the enclosing rock. Highly disseminated implies a greater degree of dispersion.
Doré
Impure and unrefined mixture of metallic gold and silver produced through the smelting of gold and silver concentrate, sand or precipitate. Typical impurities include base metals. Doré is further refined to almost pure gold by a smelter or refinery.
Drill Core
The cylindrical piece of rock, usually between one and three inches in diameter brought to surface by diamond drilling.
Environmental Impact Study
A written report, compiled prior to a production decision, that examines the effects, proposed mining activities will have on the natural surroundings.
Epithermal
A term applied to deposits containing veins and replacement bodies formed at shallow depths from ascending solutions of moderate temperatures containing precious metals (or more rarely base metals).
Feasibility study
Technical and financial study of a project at sufficient level of detail to determine whether a project should proceed. To determine the viability of a project studies are usually taken in the following order: a pre-feasibility, full feasibility and bankable feasibility.
Floatation
A milling process in which valuable mineral particles are induced to become attached to bubbles which are collected and further processed, as other materials sink.
Flotation Cells
Flotation cells are commonly used in conventional copper concentrators to separate the copper minerals from the waste rock. After being crushed and ground, the copper ore is pumped into flotation cells. Chemical reagents are added and the mixture is aerated and mechanically agitated. The mineral particles are separated from the host rock and float to the surface on air bubbles, forming a froth, which is skimmed off, filtered and dried.
Flowsheet
An illustration showing the sequence of operations, step by step, by which ore is treated in a milling, concentration or smelting process.
Geochemistry
The study of chemical properties of rocks.
Geophysics
The study of the physical properties of rocks.
Grade
Quantity of metal per unit weight of rock.
g/t
Grams per tonne, refer to grade.
Gangue
Worthless rock or other material in which valuable minerals are found.
Head grade
The average grade of ore feed to the mill.
Heap Leaching
A process whereby valuable metals (usually gold and silver) are leached from a heap, or pad, of crushed ore by leaching solutions percolating down through the heap and are collected from a sloping, impermeable liner below the pad.
Hedging
Taking a buy or sell position in a futures market that is opposite to a position held in the cash market in order to minimize the risk of financial loss from adverse price change. The most common form of hedging is the purchase of put options or forward sales.
Intrusive
A body of igneous rock formed by the consolidation of magma intruded into other rocks, in contrast to lavas which are extruded upon the surface. It is through intrusion of magma that porphyry deposits are formed.
Identified resource
Mineral occurrence in natural state quantified on the basis of geological data and an assumed cut off grade.
Indicated resource
Mineral resource sampled by drill holes and other procedures at points too widely spaced to ensure continuity but close enough to give a reasonable indication.
Inferred resource
Size of mineral resource inferred from drill holes, geoscientific evidence and other sampling procedures before testing is sufficient to allow more reliable estimation.
Leaching
A chemical process for the extraction of valuable minerals from ore: 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.
Leach pad
A large, impermeable foundation or pad used as a base for ore during heap leaching. The pad prevents the leach solution from escaping out of the circuit.
London Metals Exchange (LME)
This is the single most important metals exchange for copper and gold and is located in London.
Open-pit Mining
Open-pit mining is the most common method mining porphyry copper and these open pits account for some of the largest man made holes in the world. When determining the size of an open pit the normal ratio is 50% of the shortest distance across. In other words if a deposit is 500m long by 400m wide, the pit can be 200m deep. This is because the ramps need to be wide enough to allow large trucks to go up and down.
The open pit mine is the least expensive kind, and it is every developer's first choice where an orebody is situated close to the surface, is big enough and has little overburden.
Ore
Rock containing minerals of economic interest, extractable at a profit.
Outcrop
An exposure of rock or mineral deposit that can be seen on surface.
Overburden
The alluvium and rock that must be removed in order to expose an ore deposit.
Oxidation
A chemical reaction caused by exposure to oxygen that results in a change in the chemical composition of a mineral.
There are two major divisions of copper or gold classes found in porphyry deposits. These are oxides and sulphides. Oxide, often referred to as "supergene", is the more highly concentrated material generally found at the top of a deposit and hence is more highly desired because of the ease of processing.
Porphyries
Copper porphyries are large low-grade stockwork to disseminated deposits of copper around a large body of intrusive rock which may also carry minor recoverable amounts of molybdenum, gold and silver. They must be amenable to bulk mining methods, that is open pit or, if underground, block caving. Most deposits have copper grades of between 0.4-1%, and are up to several billion tonnes in size.
The typical porphyry copper deposit occurs in a cylindrical, stock-like, composite intrusion having an elongate or irregular outcrop about 1.5 x 2 km, often with an outer shell of equigranular medium-grained rock. The central part is porphyrite - implying a period of rapid cooling to produce the finer-grained groundmass - the porphyry part of the intrusion.
Precious Metals
Typically comprise gold, silver, platinum and palladium and are mostly used in jewellery and high end industrial applications.
Pre-Feasibility Study
A pre-feasibility study is a comprehensive study of the viability of a mineral project that has advanced to a stage where the mining method has been established, and which, if an effective method of mineral processing has been determined, includes a financial analysis based on reasonable assumptions of technical, engineering, operating, economic factors and the evaluation of other relevant factors which are sufficient for a qualified person, acting reasonably, to determine if all or part of the mineral resource may be classified as a mineral reserve.
Primary Mineralization
Valuable minerals deposited during the original period or periods of mineralization as opposed to those deposited as a result of alteration or weathering.
Proven Reserves
Reserves that have been sampled extensively by closely-spaced diamond drill holes and developed by underground workings in sufficient detail to render an accurate estimation of grade and tonnage. Also called measured reserves.
Pyrite
An iron sulfide mineral that is of little value, it is also known as "Fool's Gold" because of its bright golden colour.
Reserves
Well-defined estimate of tonnes and grade of ore. The calculated tonnage and grade of mineralization which can be extracted profitably: classified as probable and proven according to the level of confidence that can be placed in the data.
Resources
Well-defined estimate of mineralisation, not necessarily economic.
Rock chip sample
A method of sampling a rock exposure whereby a regular series of small chips of rock is broken off along a line across the face.
Scoping Study
A scoping study is the first level of study that is performed on a mineral deposit to determine its economic viability. This is usually performed to determine whether the expense of a full pre-feasibility study and later full feasibility study is warranted.
Secondary Enrichment
Secondary Enrichment refers to the process whereby a vein or mineral deposit has been enriched by minerals that have been taken into solution from one part of the vein or adjacent rocks and re-deposited in another. Secondary enrichment usually results in higher concentrations of ore although this is not always the case.
Solvent Extraction-Electro Winning (SX-EW)
A metallurgical technique, so far only applied to copper ores, in which metal is dissolved from rock by organic solvents and recovered from solution by electrolysis.
Sulphides
Minerals containing sulphur and metallic elements, often ore minerals. Copper or gold sulphide is the mineralization generally found at the bottom of a deposit.
Supergene Enrichment
A mineral deposition process in which near-surface oxidation produces acidic solutions that leach metals, carry them downward, and re-precipitate them, thus enriching sulfide minerals already present.
Copper sulphides are soluble and therefore the upper part of the orebody may be oxidized and generally leached of many of its valuable elements right down to the water table. This is called the zone of oxidation. Generally the bulk of dissolved material is carried on down to the zone of supergene enrichment.
Tailings
The material rejected from a mill after the valuable minerals have been recovered.
Vein
A zone or belt of mineralized rock lying within boundaries clearly separating it from neighbouring rock.
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