Technical Compendium of Mining Industry Jargon, Engineering Frameworks, and International Reporting Standards

Lithological and Structural Foundations in Geology and Exploration

Every mineral deposit begins as a problem in lithology, the description of a rock unit's physical character, based on its color, mineralogical composition, texture, and grain size.

Lithology is the raw substrate on which structural geologists build their models of how a deposit formed, where its boundaries lie, and where it might continue at depth.

Before a single assay is run, the geologist is reading rock: what it's made of, how it's arranged, and what that arrangement implies about the fluids that once moved through it.

Most economically significant hard-rock deposits are hydrothermal in origin: hot, chemically aggressive fluids migrate through fractures and permeable horizons in the crust, and as pressure and temperature drop, they precipitate their dissolved metal load.

The character of that fluid, its temperature, depth of formation, and the host rock it interacts with, determines what kind of deposit results. Three genetic families dominate the comparative literature:

Epithermal systems form at shallow crustal depths, typically less than about 1 kilometer, from fluids at comparatively low temperatures.

Textbook ranges vary somewhat by classification scheme, but a commonly cited window runs from roughly 50°C up toward 300°C at the higher end.

These systems produce veins and replacement bodies and are the classic host for precious metals (gold and silver) often associated with young volcanic terranes.

Porphyry deposits sit at the opposite end of the tonnage-versus-grade spectrum: large-footprint, low-grade systems associated with felsic-to-intermediate intrusive igneous rocks.

Their defining feature is the stockwork, a dense network of mineralized veinlets radiating through the host intrusion and surrounding country rock, rather than discrete high-grade veins.

Porphyries are the workhorse deposit type behind the majority of the world's mined copper and molybdenum, frequently with associated gold credits.

Skarns form differently again: coarse-grained metamorphic rocks produced when chemically reactive, silica-iron-magnesium-rich hydrothermal fluids invade carbonate host rock, typically limestone or dolomite, at an igneous contact.

The chemical reaction between fluid and carbonate host, rather than simple fracture-filling, is what generates the deposit. Skarns commonly host copper, tungsten, iron, and gold.

A fourth genetic family operates entirely differently, forming not from fluids moving through continental crust but from fluids venting directly onto the seafloor.

Volcanogenic Massive Sulfide (VMS) deposits are stratabound accumulations of metallic sulfide, dominantly copper, zinc, and lead, precipitated where submarine hydrothermal vents discharge metal-laden fluid into cold seawater.

Because massive sulfide is highly electrically conductive, VMS deposits are exceptionally good targets for electromagnetic geophysical surveys, and much of the modern VMS exploration playbook is built around that conductivity contrast.

Before a drill ever turns, geologists rely on surface indicators to vector toward buried mineralization.

A gossan is a highly porous, cellular, iron oxide- and hydroxide-rich rock formed by the weathering and oxidative breakdown of primary sulfide minerals, chiefly pyrite, at surface. Its rusty, cavernous appearance is one of the oldest visual prospecting cues in the discipline, a literal red flag for a sulfide system weathering out below.

Float works on the same principle from the opposite direction: loose fragments of rock or ore, detached from an outcrop by erosion and carried downslope or downstream, that an explorer traces uphill or upstream to locate the parent vein.

Once a target is identified, geochemistry takes over from visual prospecting. A geochemical anomaly is a localized concentration of trace elements in soil, rock, vegetation, or water that deviates meaningfully from regional background levels, the numerical signature of mineralization even where no visible outcrop exists.

That signature doesn't sit still: primary and secondary halos describe the zones of chemical dispersion that surround an orebody.

Primary halos represent element migration outward from the hydrothermally active system itself, laid down at the time of ore formation; secondary halos are a later overprint, formed by surface weathering and transport redistributing that signature closer to today's surface.

Two further distinctions anchor how deposits are evaluated and classified. The first is grade versus assay.

Grade is the metric of economic interest, the relative concentration of a target metal or mineral in the host rock, expressed in grams per tonne (g/t) for precious metals or as a percentage (%) for base metals.

Assay is the method: the chemical laboratory test performed on a physical sample to determine that precise concentration. Grade is the number; assay is how you got it.

The second distinction is hard rock versus soft rock, and it cuts across the entire discipline of mine engineering downstream.

Hard rock mining works competent igneous or metamorphic formations to win base and precious metals, and because that host rock is structurally strong, extraction is dominated by mechanical breakage, drilling and blasting or mechanical cutting against genuinely hard material.

Soft rock mining, by contrast, extracts energy resources like coal or evaporites like salt and potash from layered sedimentary basins.

Structural competence is far lower, and the geomechanics are governed by stratigraphy, bedding planes, interburden, and roof conditions, rather than the intact-rock strength that dominates hard-rock design.

Geology and Exploration Technical Glossary

Geotechnical Engineering and Spatial Configurations in Extraction and Mine Design

Once exploration confirms a deposit, the problem shifts from "where is it" to "how do we get to it and keep the ground standing while we do." Underground access is engineered through a specific vocabulary of openings, each with a distinct geometry and purpose.

An adit is a horizontal or sub-horizontal passage driven into a hillside, providing direct surface access for drainage, ventilation, or haulage, the option of choice wherever topography allows it.

A drift runs horizontally, parallel to the strike of a mineralized vein or seam, following the ore body's trend.

A crosscut, by contrast, is driven at or near a right angle to that strike, cutting across the grain of the deposit to connect parallel drifts or link access infrastructure to active production areas.

A decline is a spiral or ramped opening driven downward from surface or an upper level, engineered specifically to let rubber-tired equipment drive between levels rather than requiring hoisting.

And a shaft is the vertical or steeply inclined opening equipped with hoisting systems, the main artery for moving people, materials, and ore between surface and depth.

With access secured, the ore itself is won through stoping: the systematic drilling, blasting, and extraction of ore that leaves behind open underground cavities called stopes.

Where ground conditions are weak, operators can't simply leave those cavities open, they use cut-and-fill or backfilling systems, packing waste rock, cement, or sand into the void to provide structural support for the next extraction pass.

For flat-lying, bedded deposits, coal, salt, potash, gypsum, limestone, the layout of choice is room-and-pillar mining, extracting ore in a grid pattern while leaving rectangular or square pillars of host rock standing for support.

In coal specifically, this same underlying method has a regionally distinct name and technical variant: bord-and-pillar, standard terminology in the UK, Australia, and India, where narrow headings called bords are driven in a grid and the resulting pillars are frequently extracted later, on retreat.

It's a case where two terms describing closely related methods carry real regional and technical weight, and using them interchangeably without noting that distinction is a common source of confusion in cross-jurisdictional technical writing.

The engineering that makes room-and-pillar (or bord-and-pillar) design work is a direct calculation of load-bearing capacity.

Vertical stress is set by the weight of overburden, how deep the workings sit. Average pillar stress is then derived using tributary area theory, which assumes each pillar supports the load of the rock column directly above it plus the load that would otherwise sit above the adjacent mined-out room:

the width of the mined room or opening and width of the structural pillar left standing. Widen the room relative to the pillar, and average pillar stress climbs, the same overburden load is now being carried by proportionally less standing pillar.

The resulting Pillar Safety Factor compares that calculated stress against the rock's actual compressive strength:

The compressive strength of the pillar material. This single ratio is the load-bearing analogue of everything downstream: when average pillar stress approaches or exceeds compressive strength of the pillar material , the safety factor collapses toward — or below — 1, and the pillar is in a regime where sudden failure becomes physically possible.

That sudden failure has two names depending on commodity, though the underlying mechanism (explosive release of stored strain energy and violent spalling of overstressed pillars) is the same.

In coal, it's called a bounce or bump; in hard-rock metal mining, the equivalent event is a rockburst. Both are direct physical consequences of the stress state described by the formulas above exceeding what the rock can sustain.

Several structural elements exist specifically to manage this risk and to keep the working environment survivable.

Barrier pillars are large, deliberately unmined blocks of coal or rock left around active entries, mine boundaries, or water-bearing zones, engineered to arrest progressive structural collapse and compartmentalize hazards like water or gas inrush.

Cribbing provides supplemental structural support in the form of timber, steel, or concrete blocks built log-cabin style to absorb high, concentrated ground loads.

And because none of this matters if miners can't breathe, brattice, a fire-resistant fabric or plastic partition strung across an opening, is used to direct fresh ventilation air to the active working face rather than letting it short-circuit through the path of least resistance.

Extraction and Engineering Technical Glossary

Chemical and Physical Dynamics in Processing and Extractive Metallurgy

Extractive metallurgy is where geology becomes chemistry: the physical and chemical processes required to separate valuable metal from non-economic gangue.

The pathway runs from size reduction, through physical or chemical concentration, to final pyrometallurgical or hydrometallurgical purification.

Everything starts with comminution, the full sequence of physical size reduction, from primary crushing down to ultra-fine grinding.

This step deserves attention because it is, without much competition, the single largest electrical energy sink on a mine site.

Its purpose is liberation: breaking rock down finely enough that discrete grains of the target mineral are physically freed from the surrounding gangue matrix, so that downstream separation processes can actually act on them.

Grinding is carried out in rotating cylindrical mills, and the choice of grinding media defines the circuit type.

Autogenous grinding (AG) uses large chunks of the run-of-mine ore itself as the grinding medium, no steel media at all, which avoids that consumable cost but demands ore competent enough to do the job.

Semi-autogenous grinding (SAG) adds a supplemental charge of steel balls to assist the ore in breaking itself; operating ranges vary meaningfully by circuit and ore hardness, but published operating data generally puts typical ball charge in the range of roughly 8% to 15% of mill volume, with some circuits running as lean as 2% or as heavy as 20–22% depending on ore competency and throughput targets.

Ball mills and rod mills dispense with autogenous media entirely, using steel balls or steel rods respectively as the sole grinding medium to take coarse feed down to a fine powder suitable for downstream chemical separation.

Once ground, the slurry moves into concentration. In froth flotation, chemical reagents (collectors, frothers, and modifiers) are added to an agitated aqueous pulp.

Collectors are the working chemistry here: they selectively bind to the surface of the target mineral grains and render them hydrophobic.

Air is then injected into the flotation cell, and those hydrophobic grains attach to the rising air bubbles and float to the surface, forming a mineralized froth that is physically skimmed off as concentrate, a separation built entirely on surface chemistry rather than density or magnetism.

For oxide ores or gold-bearing material where flotation isn't the right tool, chemical leaching takes over, dissolving the target metal into a liquid lixiviant.

Heap leaching places crushed ore on an impermeable pad and irrigates it with a lixiviant appropriate to the commodity: dilute sulfuric acid for copper oxide ores, or a weak sodium cyanide solution for gold.

The solution percolates through the pile and is collected, metal-laden, at the base.

Cyanidation runs the same basic chemistry in agitated tanks rather than a static heap, finely ground gold ore mixed directly with weak cyanide solution to dissolve the precious metal quickly and completely.

Carbon-in-pulp (CIP) is the recovery step that typically follows: activated carbon granules, commonly derived from coconut shell, are added to the cyanide-gold slurry, where they adsorb the dissolved gold and allow it to be separated from the fine slurry solids ahead of final refining.

And bioleaching takes a biological rather than purely chemical route, introducing bacterial strains, Acidithiobacillus ferrooxidans is the standard workhorse organism, to oxidize sulfide-rich ore and chemically liberate gold or base metals that would otherwise remain locked inside a refractory sulfide matrix.

Where the concentrate is destined for pyrometallurgical treatment, smelting melts it at high temperature to physically separate the metal from remaining mineral impurities.

Those impurities form slag, a vitreous silicate byproduct that, being less dense than the molten metal, floats to the top of the melt and is skimmed off, leaving refined metal behind.

The processing choices made upstream have direct downstream environmental consequences, and the physics of surface area drives much of that risk.

When sulfidic ore is ground to fine particle sizes to enable flotation or leaching, its specific surface area increases enormously, and that increased surface area is precisely what makes the resulting mill tailings geochemically reactive once exposed to air and water, accelerating acid generation and heavy-metal mobilization.

Coal processing generates a structurally different waste stream: coarse coal refuse consists of larger reject rock blocks, while fine coal refuse and wash slimes are the ultra-fine carbonaceous and mineral slurries left over from washing, materials that settle far more slowly and demand entirely different containment and compaction strategies than the sand-like mill tailings from metal processing.

Processing and Metallurgy Technical Glossary

Regulatory Compliance, Environment, and International Reporting Standards

Public disclosure in mining is governed by codes designed to protect investors from the industry's oldest problem: optimistic, unverifiable resource claims.

The two dominant frameworks are the JORC Code, published by the Australasian Joint Ore Reserves Committee, and Canada's National Instrument 43-101 (NI 43-101).

Both regulate how exploration results, mineral resources, and ore reserves may be disclosed to the public, and both rest on the same underlying classification logic even though they are administered in different jurisdictions.

That classification logic runs on a strict confidence gradient. A Mineral Resource is a concentration of material of economic interest with reasonable prospects for eventual economic extraction, a standard abbreviated as RPEEE.

Resources are ranked by geological confidence: Inferred (low confidence, limited sampling), Indicated (medium confidence, sufficient for mine planning), and Measured (high confidence, with demonstrated geological and grade continuity).

None of that, on its own, is an economic promise, it's a geological one.

An Ore Reserve is where economics enters the picture. It is the economically mineable portion of a Measured or Indicated Resource, inclusive of dilution and mining losses, and it cannot be declared without at least a Pre-Feasibility Study demonstrating the extraction is genuinely economically viable.

The conversion is specific and non-interchangeable: Measured Resources convert to Proved Reserves; Indicated Resources convert to Probable Reserves.

Inferred Resources, notably, cannot be converted into any Reserve category at all, the confidence gap is considered too wide to bridge directly.

Standing behind every one of these declarations is a named, accountable individual: a Qualified Person (QP) under NI 43-101, or a Competent Person (CP) under JORC.

Both terms require a minimum of five years of relevant experience in the specific style of mineralization and deposit type under evaluation, and both carry direct personal responsibility for signing off on the resource or reserve estimate.

This is deliberately not an anonymous corporate assurance, it's a named professional putting their standing behind the number.

The bridge between a Resource and a Reserve is a set of Modifying Factors: the mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social, and governmental considerations that must all be satisfied before a Resource can be called a Reserve.

Where older studies like a Preliminary Economic Assessment (PEA) could focus almost exclusively on core engineering, mine design, metallurgical recovery, capital cost, the modern regulatory posture treats Environmental, Social, and Governance (ESG) factors as first-class Modifying Factors in their own right.

A geologically sound resource cannot become a reserve without a demonstrated, realistic path to environmental permits, waste disposal approval, and social license, including native title or community consent where applicable.

Chief among the environmental Modifying Factors is Acid Mine Drainage (AMD), also called Acid Rock Drainage (ARD): acidic, sulfate-rich water generated when pyrite (FeS₂), exposed by excavation or processing, oxidizes in the presence of water and oxygen.

The reaction proceeds in three sequential stages. First, pyrite oxidizes directly, generating ferrous iron, sulfate, and acidity.

Second, that ferrous iron oxidizes further to ferric iron. Third, the ferric iron hydrolyzes and precipitates as ferric hydroxide, releasing yet more acidity in the process.

The compounding acidity generated across these three stages is what drives the mobilization of toxic heavy metals into adjacent watersheds, and why AMD is treated as a standing, multi-generational liability rather than a short-term operating problem.

Mitigation strategies work by attacking one of the three reactants: isolating sulfidic waste under impermeable clay caps to exclude oxygen, flooding abandoned workings to the same end, or building passive wetland treatment systems and active lime-neutralization plants to intercept and buffer the acidic, metal-laden water before it reaches the wider environment.

A related but distinct regulatory concern is TENORM, Technologically Enhanced Naturally Occurring Radioactive Material.

Certain metal mining and processing operations concentrate naturally occurring uranium, thorium, and radium in sludges, scales, and dusts to levels well above natural background, requiring specialized handling, monitoring, and disposal protocols that sit outside the standard AMD framework entirely.

Finally, two royalty structures anchor much of the industry's land-access and financing agreements.

A Net Smelter Return (NSR) royalty is paid on the net revenue received from a smelter, after transportation, refining, and insurance costs are deducted, a share of gross-ish revenue, largely insulated from the operator's cost structure.

A Net Profit Interest (NPI), by contrast, is paid on the actual net profit of the operation after all operating and capital costs are deducted, a share of the upside, but one that is directly exposed to the operator's cost discipline.

Regulatory, ESG, and Business Technical Glossary

Definitive Open-Access Institutional Glossaries