Deposit type governs almost everything else about a mining project: the grades you should expect, how the ore is processed, how deep it sits, and how much of it a drill hole actually proves. A 1 g/t intercept is unremarkable in a bulk-tonnage porphyry and excellent in a narrow orogenic gold vein. The vocabulary below is what lets you tell which situation you are reading about.
The list also covers the terms that decide whether a drill result means anything — true width against downhole length, strike length, cut-off grade, and the alteration signatures that suggest a system is bigger than what has been drilled so far. These are the words that appear in every exploration release, usually without explanation.
24 terms in this section.
Chemical and physical changes to rock caused by hydrothermal fluids, often associated with mineralization. Alteration patterns help geologists identify potential ore zones and understand the processes that formed a deposit.
The chemical analysis of rock, soil, or drill core samples to determine the concentration of valuable minerals or metals. Assay results are critical for resource estimation and are typically reported in parts per million (ppm) or grams per tonne (g/t) for precious metals.
A rare earth carbonate-fluoride mineral [(Ce,La,Y)CO3F] that is the primary ore mineral for light rare earth production. Major bastnasite deposits are found in China (Bayan Obo) and the United States (Mountain Pass), accounting for most global rare earth supply.
A sediment-hosted disseminated gold deposit type named after the Carlin Trend in Nevada. These deposits contain microscopic gold in altered sedimentary rocks and are processed by heap leaching or roasting.
The minimum grade of mineralization that can be economically mined and processed. Material below the cut-off grade is considered waste, while material above it is classified as ore. Cut-off grades depend on mining costs, processing costs, metal prices, and metallurgical recovery rates.
A mineral deposit formed at shallow depths and low temperatures from hydrothermal fluids. Epithermal deposits are important sources of gold and silver and are classified as low-sulfidation or high-sulfidation based on their geochemistry.
A type of mineral deposit formed by hot, rising fluids in volcanic environments at shallow depths and low temperatures. Epithermal deposits are a major source of silver and gold, characterized by high-grade veins and stockwork mineralization.
The concentration of a valuable mineral within ore, typically expressed in grams per tonne (g/t) for precious metals like gold and silver. Higher grades indicate richer ore deposits and generally better economics. For example, 5 g/t gold means 5 grams of gold per tonne of ore.
The heavier elements in the rare earth series, including europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium. HREEs are more valuable and scarcer than light rare earths, critical for high-performance magnets and advanced technology.
The length of mineralization encountered in a drill hole, typically reported with grade information. For example, '10 meters at 5 g/t gold' means the drill hole encountered 10 meters of material grading 5 grams of gold per tonne.
The lighter elements in the rare earth series, including lanthanum, cerium, praseodymium, neodymium, promethium, and samarium. LREEs are more abundant than heavy rare earths but still economically important, particularly neodymium and praseodymium for permanent magnets.
Underground reservoirs of salty water with dissolved lithium compounds, typically found in salt flats (salars) in South America. Brine extraction involves pumping to surface evaporation ponds, offering lower production costs than hard rock mining but longer development timelines.
A continuous, well-defined mass of material containing a sufficient concentration of valuable minerals to be economically mined. The size, grade, and geometry of the orebody determine the mining method and project economics.
Gold deposits formed during mountain-building (orogenic) events, typically hosted in quartz veins within metamorphic rocks. Orogenic gold deposits are found in greenstone belts worldwide and include many historic gold mining districts.
A surficial mineral deposit formed by the concentration of heavy minerals through weathering and sedimentary processes. Placer gold deposits in streams and rivers were the target of historic gold rushes and can still be mined economically.
A mineral deposit containing economically significant quantities of two or more metals, such as copper-gold, zinc-lead-silver, or cobalt-nickel. Polymetallic deposits offer revenue diversification but require more complex metallurgy and processing.
A large, low-to-moderate grade copper deposit formed by hydrothermal fluids associated with intrusive igneous rocks. Porphyry deposits account for most global copper production and often contain significant by-products including gold, molybdenum, silver, and rhenium.
A large, low-grade disseminated ore deposit typically containing copper, molybdenum, and sometimes gold. Porphyry deposits form from hydrothermal fluids associated with intrusive igneous rocks and are among the world's largest metal sources.
A lithium-bearing mineral (LiAlSi2O6) found in pegmatite deposits. Spodumene is the primary source mineral for hard rock lithium production and must be processed through chemical conversion to produce battery-grade lithium carbonate or hydroxide.
A complex network of small veins or veinlets forming a three-dimensional mesh in rock. Stockwork mineralization is common in porphyry and some gold deposits, where multiple generations of veining create economic grades.
The horizontal distance along which a mineralized zone extends. Greater strike lengths indicate larger potential deposits and are important factors in resource estimation and mine planning.
The actual thickness of a mineralized zone measured perpendicular to its orientation. Drill holes rarely intersect mineralization at perfect right angles, so true width calculations are necessary to estimate tonnage accurately.
A sheet-like deposit of minerals that fills a fracture or fault in rock. Many gold deposits occur in quartz veins where gold was deposited from hydrothermal fluids. Veins can range from millimeters to meters in width.
A type of metal sulfide ore deposit formed on the seafloor from hydrothermal vents in volcanic environments. VMS deposits typically contain copper, zinc, lead, gold, and silver in massive sulfide lenses. Found in ancient volcanic sequences now exposed on land.