Glossary of Geological & Mining Terms
Plain-English definitions of the geology, exploration, and capital-markets terminology used throughout Eastfield's project and investor pages.
This glossary provides general educational information about mineral exploration. For information concerning Eastfield's mineral projects, readers should refer to the Company's project disclosures, news releases and continuous-disclosure filings on SEDAR+.
Geology
16 termsAlaskan-Type Complex
An Alaskan-type (or Ural-Alaskan) complex is a concentrically zoned mafic-ultramafic intrusion, typically with a dunite core grading outward through pyroxenite to hornblendite and gabbro. These bodies are recognised hosts for platinum-group element and associated copper-cobalt mineralization linked to chromite-rich and sulphide-bearing zones. Their distinctive geophysical signature makes them attractive critical-minerals targets.
Chalcopyrite
Chalcopyrite is a copper-iron sulphide mineral (CuFeS₂) and the single most economically important source of copper worldwide. It has a distinctive brassy-yellow colour and occurs as disseminated grains, veinlets, and fracture coatings in porphyry and many other deposit types. In porphyry systems chalcopyrite commonly carries associated gold, making it a key target mineral.
Dip
Dip is the angle, measured from the horizontal, at which a geological surface such as a bed, fault, or vein is inclined. It is recorded in the direction of steepest descent and is always perpendicular to strike. Knowing the dip of a mineralized structure is essential for orienting drill holes so they intersect the target as close to true width as possible.
Gossan
A gossan is a weathered, iron-oxide-rich zone that forms at surface where sulphide minerals have oxidised and leached away. Its characteristic rusty red-brown staining can be visible from the air and on the ground, making gossans classic exploration vectors toward buried sulphide mineralization. Geologists sample gossans carefully because the original metals may have been redistributed during weathering.
Hydrothermal Alteration
Hydrothermal alteration is the modification of a rock's original minerals by hot, chemically active fluids circulating through the crust. These fluids transport metals and leave behind distinctive new mineral assemblages — such as potassic, phyllic, or propylitic zones — that form predictable patterns around many ore deposits. Mapping alteration is a primary exploration tool because the zones act as a vector pointing toward the mineralized centre.
Mineralization
Mineralization refers to the introduction or concentration of economically interesting minerals — such as copper, gold, or platinum-group sulphides — into a host rock. It is the geological phenomenon that explorers seek to find, map, and ultimately quantify. The style, intensity, and continuity of mineralization determine whether a showing might eventually support a mineral resource.
Phyllic Alteration
Phyllic alteration, also called sericitic alteration, is characterised by quartz, sericite (fine-grained white mica), and abundant pyrite. It typically forms an intermediate-temperature zone that overprints earlier potassic alteration in the upper and outer parts of porphyry systems. The high pyrite content of phyllic zones produces strong geophysical and geochemical responses that explorers use as targeting vectors.
Platinum-Group Elements (PGE)
The platinum-group elements (PGE) are a family of six chemically related precious metals: platinum, palladium, rhodium, ruthenium, iridium, and osmium. They are most commonly concentrated in magmatic sulphide and chromite-bearing zones within mafic-ultramafic intrusions. Strong demand from catalytic converters, hydrogen technologies, and other industrial uses gives PGE prominence among critical-minerals exploration targets.
Potassic Alteration
Potassic alteration is a high-temperature hydrothermal assemblage characterised by potassium-bearing minerals such as secondary biotite and potassium feldspar. In porphyry copper systems it typically forms the innermost, hottest alteration zone and is closely associated with the bulk of the copper-gold mineralization. Recognising potassic alteration helps geologists locate the centre of a porphyry system.
Propylitic Alteration
Propylitic alteration is a lower-temperature hydrothermal assemblage dominated by chlorite, epidote, calcite, and pyrite. It usually forms the outermost and most extensive alteration halo around porphyry and related systems, often extending well beyond the mineralized core. Because it is broad and easily recognised in the field, propylitic alteration is a useful early indicator that a larger system may be present.
Pyrite
Pyrite is an iron sulphide mineral (FeS₂) with a pale brassy colour, often nicknamed "fool's gold". Although pyrite itself is not an ore of iron, its abundance in and around many deposits makes it an important indicator: pyrite-rich rocks produce strong geophysical chargeability responses and can host or accompany gold. Distinguishing pyrite from valuable sulphides such as chalcopyrite is a routine but essential field skill.
Quesnel Trough (Quesnellia)
The Quesnel Trough is a long, mineral-endowed belt within the Quesnel Terrane (Quesnellia) of British Columbia. It is host to a series of important alkalic and calc-alkalic porphyry copper-gold deposits developed in Triassic-Jurassic arc rocks. Its established mineral endowment makes the trough a favoured setting for copper-gold exploration.
Stikine Terrane (Stikinia)
The Stikine Terrane, or Stikinia, is one of the large accreted terranes that make up central and northwestern British Columbia. It is renowned for hosting many of the province's significant porphyry copper-gold deposits, developed within Jurassic volcanic and intrusive rocks. Properties situated in Stikinia are commonly explored with porphyry-style targeting models.
Strike
Strike is the compass bearing of a horizontal line lying within an inclined geological surface, such as a rock layer, fault, or vein. Together with dip, strike describes the three-dimensional orientation of a structure and is fundamental to mapping and drill planning. Describing a target as "open along strike" means mineralization may continue laterally beyond the area tested.
Terrane
A terrane is a fault-bounded fragment of the Earth's crust that has a stratigraphy, structure, and geological history distinct from adjacent blocks. The Canadian Cordillera, including most of British Columbia, is an assembly of terranes that were accreted onto ancestral North America over hundreds of millions of years. Understanding which terrane a property lies within helps predict the styles of mineralization that may be present.
Ultramafic Rock
Ultramafic rocks are igneous rocks with very high magnesium and iron contents and very low silica, including types such as dunite, pyroxenite, and peridotite. They crystallise from primitive, mantle-derived magmas and are important exploration targets because some host magmatic sulphide accumulations of nickel, copper, and platinum-group elements. In Alaskan-type complexes, ultramafic rocks are spatially associated with copper-PGE-cobalt mineralization.
Deposit Types
5 termsEpithermal Deposit
Epithermal deposits form at shallow crustal levels (typically less than about one kilometre depth) from low-temperature hydrothermal fluids, commonly in volcanic settings. They host gold and silver in veins, stockworks, and breccias and can carry high precious-metal grades. Epithermal systems frequently occur in the upper or peripheral parts of larger porphyry systems, so the two are often explored together.
Magmatic Sulphide Deposit
Magmatic sulphide deposits form when an immiscible sulphide liquid separates from a cooling mafic or ultramafic magma and concentrates metals such as nickel, copper, cobalt, and platinum-group elements. The dense sulphide droplets settle and accumulate, sometimes forming massive to disseminated sulphide zones. These deposits are key sources of nickel and PGE and are explored using geophysics and geochemistry tuned to ultramafic hosts.
Massive Sulphide
Massive sulphide refers to rock that consists predominantly of sulphide minerals (generally more than about 50% by volume) rather than disseminated grains. Such accumulations can host significant copper, zinc, lead, nickel, gold, or silver depending on the geological setting. Because dense, conductive massive sulphides respond strongly to electromagnetic and other geophysical methods, those tools are central to finding them.
Orogenic Gold Deposit
Orogenic gold deposits (also called lode or mesothermal gold) form during regional mountain-building when metamorphic fluids deposit gold in quartz-carbonate veins along faults and shear zones. They are typically high-grade but structurally complex, with gold tied closely to the geometry of the controlling structures. The Cariboo and other parts of the British Columbia Cordillera have a long history of orogenic and related lode-gold production.
Porphyry Copper Deposit
Porphyry copper deposits are large-tonnage, relatively low-grade copper deposits, often with significant gold or molybdenum credits, that form around shallow intrusive porphyry stocks. Copper occurs mainly as disseminated and veinlet-hosted chalcopyrite within zoned alteration halos. Although individual grades are modest, their enormous size makes porphyry deposits the world's primary source of copper and a central target in British Columbia exploration.
Exploration Methods
12 termsAirborne Survey
An airborne survey collects geophysical data — commonly magnetic, electromagnetic, or radiometric measurements — using sensors carried by a fixed-wing aircraft, helicopter, or drone. Flying allows rapid, systematic coverage of large or rugged areas that would be slow to survey on the ground. Airborne datasets are typically used to define regional structures and prioritise targets for ground follow-up.
Anomaly
An anomaly is any measurement — geochemical, geophysical, or geological — that stands out from the surrounding background values. Anomalies are the fundamental output of exploration surveys because they flag where conditions differ from the norm and may indicate concealed mineralization. Not every anomaly reflects ore, so geologists evaluate each in its geological context before advancing it as a drill target.
Chargeability
Chargeability is the quantity measured by an induced-polarization survey, describing how strongly the ground retains an induced electrical charge after the current is switched off. High chargeability commonly reflects disseminated sulphide minerals, so chargeability anomalies are prime porphyry exploration targets. Geologists interpret chargeability together with resistivity and geology to distinguish ore-related sulphides from barren graphite or clay.
Electromagnetic (EM) Survey
An electromagnetic (EM) survey uses transmitted electromagnetic fields to detect contrasts in the electrical conductivity of the ground. Conductive bodies such as massive sulphides, graphite, or saline water produce measurable responses, making EM particularly useful for nickel-copper-PGE and other sulphide targets. EM can be deployed from the air, on the ground, or in boreholes depending on the depth and scale of interest.
Geochemical Survey
A geochemical survey involves collecting samples of rock, soil, stream sediment, or vegetation and analysing them for trace concentrations of metals and pathfinder elements. Patterns of elevated values, called anomalies, help explorers narrow large areas down to prospective ground. Geochemistry is a low-cost, early-stage tool that guides where to focus more expensive geophysics and drilling.
Geological Mapping
Geological mapping is the systematic field recording of rock units, structures, alteration, and mineralization onto a base map. It provides the geological framework that ties together geochemical and geophysical data and underpins target generation. Careful mapping, including the measurement of strike and dip, is essential before designing trenches or drill holes.
Geophysical Survey
A geophysical survey measures contrasts in physical properties — such as magnetism, electrical conductivity, density, or chargeability — to image rocks and structures that are concealed beneath surface cover. Different methods respond to different deposit types, so surveys are chosen to match the target model. Geophysics bridges the gap between surface geochemistry and drilling by helping define targets in three dimensions.
Induced Polarization (IP)
Induced polarization (IP) is an electrical geophysical method that measures how the ground temporarily stores electrical charge, a property quantified as chargeability. Disseminated sulphide minerals such as pyrite and chalcopyrite produce strong IP responses, making the method especially effective for porphyry copper targeting. IP surveys are commonly combined with resistivity measurements to map both sulphide content and rock type.
Magnetic Survey
A magnetic survey measures small variations in the Earth's magnetic field caused by differing concentrations of magnetic minerals such as magnetite in the underlying rocks. The resulting maps help interpret lithology, structure, and alteration, and can highlight intrusions or magnetite-bearing zones associated with mineralization. Magnetics are inexpensive, can be flown over large areas, and are often the first geophysical layer acquired on a project.
Rock Grab Sample
A rock grab sample is an individual, selectively collected piece of rock taken to determine the metal content of an outcrop, boulder, or mineralized showing. Because the sampler chooses the material, grab samples are inherently selective and may not represent average grade over any width. NI 43-101 requires that grab-sample results be described carefully and not presented as if they reflect a deposit's overall tenor.
Soil Sampling
Soil sampling is a geochemical method in which soils are collected systematically, usually on a grid, and analysed for metal content. Because metals can disperse upward and outward from concealed mineralization, coherent soil anomalies can outline drill targets even where bedrock is not exposed. It is a cost-effective technique widely used in early-stage exploration.
Trenching
Trenching involves digging or blasting shallow channels to remove soil and weathered overburden and expose fresh bedrock for mapping and continuous channel sampling. It provides better-controlled, more representative grade information than scattered grab samples and bridges the gap between surface geochemistry and drilling. Trenching is most useful where mineralization is shallow and overburden is thin.
Drilling
6 termsAssay
An assay is the laboratory determination of the concentration of one or more metals in a rock, soil, or core sample, typically reported in grams per tonne or percent. Assays convert physical samples into the quantitative grade data that underpin resource estimates and exploration decisions. Reliable assays depend on rigorous sample preparation and quality-control procedures.
Diamond Drilling
Diamond drilling uses a rotating, diamond-impregnated bit to cut a continuous cylindrical sample of rock, known as core, from depth. Because it preserves the rock's structure, mineralogy, and grade relationships intact, diamond drilling is the principal method for confirming and quantifying mineralization. It is more costly than other drilling methods, so targets are usually well defined by geology, geochemistry, and geophysics first.
Drill Core
Drill core is the solid cylinder of rock produced by diamond drilling. Geologists log the core in detail — recording lithology, alteration, structure, and mineralization — before splitting or cutting it so that half can be sent for assay and half retained as a permanent record. Core provides the most reliable, continuously sampled view of what lies beneath a target.
Drill Intercept
A drill intercept is a reported interval of mineralization in a drill hole, expressed as a grade over a downhole length (for example, grade over a number of metres). Intercepts are the headline results of drill programs but must be read carefully, because downhole length is usually greater than the true width of the mineralized zone. Under NI 43-101, intercepts must be verified and contextualised by a Qualified Person.
QA/QC (Quality Assurance / Quality Control)
QA/QC refers to the quality-assurance and quality-control protocols used to verify that exploration data are reliable. In practice this includes inserting certified reference standards, blanks, and duplicate samples into the sample stream and monitoring laboratory performance. Robust QA/QC is required under NI 43-101 because resource estimates and investment decisions depend on the integrity of the underlying assay data.
True Width
True width is the real thickness of a mineralized structure measured at right angles to its boundaries, as opposed to the apparent (downhole) width seen when a drill hole crosses it obliquely. Because a hole rarely intersects a body exactly perpendicular, downhole intercept lengths usually overstate true thickness. Responsible reporting states whether widths are true or apparent so investors are not misled.
Regulatory & Reporting
7 termsForward-Looking Statements
Forward-looking statements are disclosures about anticipated future events, plans, or results — such as planned drill programs or expected outcomes — that are inherently uncertain. Securities laws require companies to identify these statements and accompany them with cautionary language and risk factors. Investors should treat forward-looking statements as expectations, not guarantees, because actual results may differ materially.
Mineral Reserve
A mineral reserve is the economically mineable portion of a measured or indicated mineral resource, demonstrated by at least a pre-feasibility study that applies modifying factors such as mining, processing, economic, and regulatory considerations. Reserves are classified as probable or proven and represent a higher level of confidence than resources. Converting resources to reserves is a major value milestone but lies well beyond early-stage exploration.
Mineral Resource
A mineral resource is a concentration of mineralization in the Earth's crust, in such form, grade, and quantity that there are reasonable prospects for eventual economic extraction. Resources are classified as inferred, indicated, or measured according to increasing geological confidence. A mineral resource is not the same as a mineral reserve and does not by itself demonstrate that mining would be profitable.
NI 43-101
National Instrument 43-101 (Standards of Disclosure for Mineral Projects) is the Canadian securities rule that governs how companies publicly disclose scientific and technical information about mineral projects. It requires that material disclosure be based on work supervised or approved by a Qualified Person and sets standards for resource and reserve reporting. The rule exists to protect investors by ensuring disclosure is accurate, balanced, and not misleading.
Qualified Person (QP)
A Qualified Person (QP) is an engineer or geoscientist with the experience, professional registration, and relevant expertise required by NI 43-101 to take responsibility for a project's scientific and technical disclosure. The QP verifies data, supervises or approves technical reports, and stands behind the resulting public statements. Investors rely on the QP designation as assurance that disclosure meets professional and regulatory standards.
SEDAR+
SEDAR+ is the electronic filing system operated by the Canadian Securities Administrators where reporting issuers file public disclosure documents, including financial statements, news releases, and NI 43-101 technical reports. It gives investors free access to a company's official filings. Checking SEDAR+ allows investors to read the primary documents behind a company's public statements.
Technical Report
A technical report is a formal document prepared under NI 43-101 by or under the supervision of one or more Qualified Persons to support a company's material scientific and technical disclosure. It summarises geology, exploration, data verification, and, where applicable, resource or reserve estimates and economic analysis. Technical reports are filed publicly so investors can review the basis for a company's claims.
Capital Markets
10 termsCarried Interest
A carried interest is an ownership stake in a project whose share of costs is paid (carried) by another partner up to an agreed milestone, such as a production decision. The carried party retains its percentage interest without contributing capital during the carry period, preserving treasury while staying exposed to success. Carried interests are frequently negotiated by project generators within option and joint-venture deals.
Earn-In
An earn-in is the mechanism within an option or joint-venture arrangement by which a partner progressively earns a defined ownership percentage in a project by funding exploration and making required payments. Earn-in terms specify the spending and milestones needed to vest each tranche of interest. The structure lets the original owner advance a project with limited capital outlay while sharing future upside.
Joint Venture (JV)
A joint venture (JV) is a contractual arrangement in which two or more parties hold and develop a mineral project together, sharing costs, decisions, and benefits in proportion to their interests. JVs commonly form after a partner completes an earn-in, converting the option relationship into co-ownership. Partners that elect not to fund their share may be diluted under the JV terms.
Market Capitalization
Market capitalization is the aggregate market value of a company's outstanding shares, found by multiplying the share price by the number of shares outstanding. For junior explorers it provides a quick gauge of size and how the market values the company's projects and treasury. Because junior valuations are speculative and sentiment-driven, market capitalization can move sharply on exploration news.
Net Smelter Return (NSR)
A net smelter return (NSR) is a royalty calculated as a percentage of the revenue from metal production after deducting certain costs such as smelting, refining, and transportation. NSRs let a former owner retain ongoing exposure to a mine's cash flow without bearing operating or capital costs. They are a common way for project generators to keep long-term upside after optioning a property.
Option Agreement
An option agreement is a contract in which one party (the optionee) earns the right to acquire an interest in a mineral project by completing agreed payments, share issuances, and exploration expenditures over time. It lets a project owner advance a property using a partner's capital while retaining an interest until the option is exercised. Option agreements are a core tool of the project-generator model.
Project Generator
A project generator is a junior exploration company that acquires and advances a portfolio of projects and then options or joint-ventures them to partners who fund the most expensive work, such as drilling. This model spreads risk across multiple properties and preserves the generator's treasury and share structure while retaining exposure to discovery. It trades some upside on any single project for diversification and reduced dilution.
TSX Venture Exchange (TSX-V)
The TSX Venture Exchange (TSX-V) is a Canadian public market for early-stage and emerging companies, on which many junior mineral explorers are listed. It provides access to risk capital and a regulated venue for trading, subject to continuous-disclosure and listing requirements. A TSX-V listing brings obligations under securities law, including NI 43-101 disclosure for technical information.
Want the bigger picture? Read our plain-English explainers on deposit geology, exploration methods, and investing in junior miners.