Delving into the rich history of mineral extraction reveals a specialized lexicon, essential for understanding the trials, triumphs, and techniques of prospectors and miners. This comprehensive glossary of mining terms provides insight into the language that shaped an industry, from the early gold rushes to the complex operations of today. Understanding these mining terms is crucial for anyone interested in the heritage and evolution of mining, offering a window into a world often hidden beneath the earth’s surface, particularly in regions renowned for their rich mineral deposits.
A
Adit – An entrance to a mine, typically a horizontal tunnel driven into the side of a hill or mountain. Adits serve various purposes, including drainage, ventilation, and access for ore removal.
Alluvial or Bench Deposits – These refer to ancient river-washed rock and gravel bars, which can be located thousands of feet from modern streams, creeks, or rivers. Alluvial deposits often hold untapped potential for finding gold because such areas may have never been thoroughly worked. Historically, hydraulic giants were extensively used to process these types of deposits.
Alluvium – A geological deposit of loose gravel, sand, silt, or clay, typically found between the superficial covering of vegetable mold and the underlying bedrock. It is often deposited by moving water.
Amalgam – A metallic alloy of mercury with another metal, most commonly gold or silver. In historical mining, mercury was used to chemically bind with precious metals.
Amalgamation – The specific technique of using mercury to attract small particles of crushed gold or silver and join them into an amalgam. The gold or silver could then be recovered by distilling off the mercury, a process that, while effective, carried significant environmental and health risks.
Ancient Riverbed Claims – These claims specifically target gold found in the beds of now-extinct or re-routed rivers, which often hold significant concentrations of placer gold.
Arastra – A primitive but effective mill used for grinding ore. It consists of one or more large stones dragged in a circular motion on a paved bed, crushing the ore through friction and weight.
Argentiferous – A descriptive term meaning bearing or producing silver, often applied to ores or geological formations rich in silver content.
Assaying – The process of chemically analyzing ore or bullion to determine the percentage of a given metal (like gold, silver, or copper) it contains, crucial for valuation.
Assessment – In mining finance, this refers to an amount levied on capital stock, often to fund ongoing operations or exploration.
B
Bar Claims – These are mining claims where gold or other minerals are found in low collections of sand or gravel within rivers, typically exposed during periods of low water.
Barren Contract – Refers to a section of a contract vein, or a specific place within it, where no valuable mineral deposits are found, indicating a lack of pay dirt.
Base Bullion – Precious metals (such as gold or silver) that are still contained within a lead alloy, typically requiring further refining to separate the pure metals.
Bedrock – The solid rock formation that underlies the more superficial layers of soil, gravel, or pay dirt. It is often the ultimate resting place for heavy minerals like gold in placer deposits.
Bench Claims – Claims for minerals found in a narrow tableland or terrace located on a hillside, typically situated above a river or stream where ancient deposits may reside.
Blende – A common ore of zinc, chemically composed of zinc and sulfur (zinc sulfide), known for its distinct metallic to submetallic luster.
Blind Lode – A lode or vein of mineral that does not have an outcrop, meaning it is not visible at the surface and must be discovered through subsurface exploration.
Blossom Rock – Also known as float ore, this refers to loose rock or isolated masses of ore found on the surface or near where lodes or ledges outcrop, having become detached from the main formation due to weathering and erosion.
Bonanza – A Spanish term literally meaning good luck or fair weather, but in mining, it signifies a mine that is yielding a substantial profit or a particularly rich strike of ore. A mine is “en bonanza” when it is highly productive.
Breasting Ore – The specific act of extracting ore from the working face, breast, or end of a tunnel or drift. It is the active removal of valuable material.
Bullion – Refers to precious metals, such as gold or silver, in bulk form (e.g., bars or ingots) before they have been coined or processed into other finished products.
Bucket Line Dredge – A large and complex piece of mining equipment, unlike modern suction dredges. These massive machines would scoop up vast amounts of water and gravel using an endless chain of buckets and then run the material through a long sluice box to recover minerals.
C
Cage – An essential piece of equipment in vertical shaft mines, serving as an elevator for hoisting and lowering ore cars, personnel, and mining materials safely within the shaft.
Cap Rock – A geological formation that overlays the ore body or vein stone, often acting as an impermeable barrier or a distinct layer above the valuable deposit.
Carbonate – In the context of silver mining, this refers to a geological formation or ore type that carries significant silver ore, often ranging from 5 to 70 percent of lead content alongside the silver.
Carboniferous – A geological term indicating the presence of coal or coal-bearing strata within a rock formation, particularly prevalent during the Carboniferous period.
Chilean Mill – A grinding machine somewhat similar to an arrastra, where heavy stone wheels turn about a central shaft, crushing ore through both grinding and impact forces.
Chlorides – A chemical compound primarily consisting of chlorine and silver, typically referring to silver chloride ores which were a significant source of silver in many historic districts.
Chute – An inclined channel or passage through which ore or other mined material slides by gravity from a higher level to a lower one, often used for loading ore cars.
Chopping – Refers to the visible rock or mineral indications that appear on the surface, signifying the potential presence of an underlying lode or vein.
Claim – A legally defined piece of land, typically 25 to 300 feet wide and 1,500 feet long, which a government grants or recognizes to an individual who discovers minerals within its boundaries, establishing possessory rights for mining.
Conglomerate – A type of clastic sedimentary rock composed of rounded fragments (pebbles, cobbles, or boulders) cemented together in a matrix, often referred to as pudding stones.
Contact – In geology, this describes the touching, meeting, or junction of two different kinds of rock, such as porphyry and slate, which can often be zones of mineralization.
Contact Vein – A mineral vein that is situated along the contact plane of, or precisely between, two dissimilar rock masses, often indicating a favorable environment for ore deposition.
Cord of Ore – A traditional unit of measurement for broken ore, equivalent to 128 cubic feet. In quartz rock, this volume typically weighs approximately seven tons.
Cornish Pump – A highly robust and efficient type of reciprocating steam pump, developed in Cornwall, England. It was commonly used in 19th-century deep mines to effectively raise large quantities of underground water, preventing flooding.
Crosscut – A horizontal tunnel or passage driven perpendicular to the main direction or strike of a vein or ore body. Its purpose is often to explore for parallel veins or to provide access to different parts of the mine.
Country Rock – The barren rock formation found on either side of a lode, ledge, or vein. It is the permanent rock that encloses the valuable mineral deposit.
Coyote – A specific digging method used in river-borne gravel, involving tunneling horizontally until bedrock is reached. This tunnel is meticulously dug to locate and extract rich bedrock deposits deep within a gravel bar.
Crevice – A narrow opening, crack, or fissure in rock formations, which can sometimes contain concentrations of minerals or gold.
Cribbing – A timber or plank lining used to support the walls of a shaft or drift, preventing collapse and confining loose wall-rock. It is a critical component of mine safety and structural integrity.
CrossCut – A level driven across the course of a vein, often for exploration or access.
Cupriferous – A descriptive term indicating that something contains copper or is capable of producing copper, commonly applied to copper-rich ores or regions.
D
Debris – General term for sediment, rock fragments, and waste material that accumulates from mining operations, often discharged into natural water systems.
Denudation – The process by which rocks and landforms are laid bare or worn away by natural agents such as running water, ice, or wind, often exposing underlying geological features or mineral deposits.
Deposit – A significant body of ore or mineral wealth that is distinct from a mere ledge or vein, suggesting a larger, more concentrated accumulation.
Diggings – A colloquial term applied to placer mining sites or areas where active mineral extraction is taking place, especially in historical contexts.
Diluvium – A geological deposit composed of superficial sand, loam, gravel, pebbles, and other unconsolidated material, often associated with ancient flood events.
Dip – The slope, pitch, or angle that a vein, lode, or rock stratum makes with the plane of the horizon. Understanding the dip is crucial for planning underground mining operations.
Dredge – A common piece of mining equipment, historically designed to suck up dirt and gravel from within a stream bed or river bottom using water pressure, separating out heavier minerals like gold.
Drift – A horizontal underground passage excavated along the strike of a rich ore vein. Drifts are primarily used in hard rock mining to follow and extract the valuable mineral deposit.
Dry Diggings – Refers to areas where earth and gravel were excavated in the dry season (summer) and then stockpiled to be washed in the winter when water became more plentiful, a common practice in arid mining regions.
Dry Washing – A method of recovering gold in arid environments where water is scarce. Fine soil and lighter materials are blown away by wind or forced air, leaving the heavier gold particles behind.
Drywasher – A specific desert mining tool, similar in function to a high banker but designed to operate without water. It uses forced air or wind to separate light waste material from heavier gold in a specialized sluice box.
Dump – A pile of ore, waste rock, or debris removed from mines, or tailings (processed waste material) resulting from sluicing or milling operations.
E
End Lines – The legal boundaries that define the ends of a mining claim, particularly important in determining the extent of a claim holder’s extralateral rights along a vein.
F
Face – The actively worked end of a level, drift, or tunnel where ore or rock is currently being excavated. It is the leading edge of mining operations.
Fathom – A unit of measurement, specifically six feet square on a vein, used to quantify the extent of a mineral body or excavation.
Feeder – A smaller vein or stringer of mineralized material that branches off or joins a larger, more significant ore vein, often contributing to its overall richness.
Feldspar – A group of crystalline minerals consisting of aluminum silicates with either potassium, sodium, calcium, or barium. Feldspars are essential constituents of nearly all crystalline (igneous and metamorphic) rocks and are very common rock-forming minerals.
Fissure Vein – A geological formation consisting of a crack or fracture (fissure) in the earth’s crust that has subsequently been filled with mineral matter, often containing valuable ores.
Flat Claims – Mining claims specifically located on flat terrain, usually referring to placer deposits found in broad, level areas rather than in riverbeds or hillsides.
Flour Gold/Gold Dust – Gold particles that are so exceedingly fine that they resemble flour or dust in texture. While plentiful, they are challenging to recover due to their small size and buoyancy.
Float – Loose rock, isolated masses of ore, or fragments of ore that have become detached from their original formation (the lode) and are found scattered on the surface or in superficial deposits.
Flume – A constructed boxing or piping system designed for carrying water, often over uneven terrain. Similar to sluice boxes but without riffles, flumes are solely used for water transport in areas where ditches are impractical, such as cliffsides.
Flux – A substance, often a mineral, added to ore in the furnace of a smelter to promote melting and assist in separating the desired metal from impurities by forming a slag.
Footwall – The layer of rock immediately underlying a vein or ore body. Miners historically referred to it as the wall upon which they would stand.
Forfeiture – The loss of a mining claim or property due to a failure to comply with legal requirements, such as performing the prescribed quantity of annual assessment work.
Free Gold – Gold that is easily separated from the surrounding quartz rock or dirt without complex chemical processing, typically found in its native metallic state.
G
Galena – A common and historically significant lead ore, chemically composed of sulfur and lead (lead sulfide), recognized by its distinctive metallic luster and cubic crystals.
Gangue – Refers to the worthless rock or mineral material that is intimately mixed with and encloses the valuable metals within a vein or ore body. It is the waste material that must be separated from the ore.
Gash Vein – A type of vein that is characteristically wide above and progressively narrows as it extends downward, often filling irregular fractures in soluble rocks.
Geode – A geological formation consisting of a cavity within a rounded stone or rock mass, whose inner surface is studded with crystals or other mineral matter, typically forming inwardly.
Geology – The scientific study of the Earth’s physical structure, substance, history, and the processes acting upon it. In mining, it involves understanding rock formations, mineral deposits, and their genesis.
Grizzly – A set of parallel bars or gratings, typically made of heavy timber or metal, set into a flume or sorting platform. Its purpose is to strain out and separate large stones and debris from finer material, particularly used in hydraulic mining.
Gulch – A narrow and deep ravine, especially one marking the course of a torrent or stream, often a site for placer mining.
Gulch Claims – Mining claims for minerals found within gullies or narrow ravines, which are often dry for part of the year but can carry significant placer deposits during seasonal flows.
H
Hanging Wall – The layer of rock or wall that lies immediately over a lode or vein. Miners historically referred to it as the wall that seemed to “hang” over their heads.
Hard Rock Mine – A type of mine characterized by tunnels and shafts dug into solid rock formations, specifically for the purpose of finding and extracting valuable rocks, minerals, or metals embedded within the rock itself, as opposed to placer deposits.
Heading – In underground mining, this term refers to the vein or ore body situated above the level of a drift or working passage.
Headings – In placer mining, this specifically refers to the mass of gravel or pay dirt situated above the head (intake) of a sluice, waiting to be processed.
Highbanker – A portable and mobile sluice box system. Unlike traditional sluice boxes placed directly in a creek, a highbanker uses a pump to draw water and transport both water and mineral-bearing material to its elevated sluice, allowing for processing away from the immediate water source and often processing more material efficiently.
High-Grade Ore – Ore that contains a particularly rich concentration of valuable metals. In the historical context provided, it was often defined as ore containing more than 20 ounces of silver per ton, with 50 percent or more lead content.
High Grading – A colloquial term, often with negative connotations, referring to the act of a miner stealing valuable nuggets or rich ore directly from the sluice boxes or ore chutes, bypassing official measurement.
Hill Claims – Mining claims for minerals found in or directly under a hill, often implying hard rock lode deposits rather than placer formations.
Horse – In mining geology, this refers to a mass of barren rock matter that occurs within or between the branches of a vein, essentially a non-mineralized inclusion within the ore body.
Hydraulic Claims – Mining claims that are specifically worked or exploited using hydraulic power, typically involving powerful jets of water to dislodge and process material.
Hydraulic “Giant” or Monitor – A powerful, firehose-type nozzle used in hydraulic mining. These giants sprayed vast amounts of high-pressure water onto hillsides and gravel banks to wash away overlying material and expose gold-bearing layers.
I
Inch of Water – A historical unit of water measurement, approximately two and a half cubic feet per minute. It refers to the volume of water that will flow out of an opening one inch square under specific pressure conditions.
Incline – A slanting shaft or tunnel in a mine, dug at an angle rather than vertically or horizontally. Incline shafts are used to follow dipping veins or to provide access to different levels.
J
Jumping a Claim – The act of illegally or improperly relocating a mining claim, often on ground where the original claim holder has failed to perform the required annual assessment work, thereby forfeiting their rights.
K
Knife Claims – A type of placer mining claim where minerals, particularly gold, are dug from narrow crevices or cracks in bedrock using simple tools like a knife or spoon, due to their accessibility.
Kibble – An iron bucket, often of Cornish origin, specifically designed and used in early mining operations to hoist ore, waste rock, and sometimes miners themselves to the surface from shafts.
L
Level – A horizontal tunnel or passage excavated along the course of a vein or ore body from the main shaft or tunnel. It is essentially a drift used for extraction and exploration.
Ledge – Another term for a vein or lode, referring to a distinct body of mineralized rock, often appearing as a prominent geological feature.
Little Giant – A smaller, more portable version of the hydraulic giant or monitor, a movable nozzle attached to hydraulic pipes used for directing powerful jets of water in mining operations, particularly in smaller-scale hydraulic mining.
Locate – To establish the legal possessory right to a mining claim by following the prescribed procedures, which typically involve discovery of minerals, marking boundaries, and filing paperwork.
Lode – A metallic vein, typically a fissure or fracture in rock filled with mineral-bearing material. Lode mining involves extracting minerals directly from these veins in solid rock.
Long Tom – A piece of placer mining equipment, similar to a sluice box but typically longer and narrower. It was used to wash gold-bearing gravels, separating the gold from lighter materials.
Low-grade Ore – Ore that contains a relatively small or uneconomical concentration of valuable metals. In the historical context provided, it was defined as ore containing below 20 ounces of silver per ton, with a lead content of 50 percent of the total ton or less.
M
Metamorphism – A fundamental geological process involving a pronounced change in the constitution, texture, or structure of rock, primarily affected by intense pressure, heat, and the presence of water. This often results in a more compact and highly crystalline condition, sometimes leading to the formation of new minerals.
Mill Run – A test conducted to assess the quality and recoverability of ore after it has undergone reduction or processing through a mill. It provides an indication of the potential yield.
Mineral – A naturally occurring substance, typically inorganic, with a definite chemical composition and an ordered atomic structure. It may or may not be of economic value, often appearing in crystal or grain form within the Earth’s crust.
Mother Lode – A primary, extensive, and rich vein of gold-bearing quartz within a mountain or geological formation. Land erosion causes gold to break away from this source, eventually washing into rivers to form placer deposits. The term often implies the ultimate source of a region’s gold.
Conclusion
The intricate world of mining is deeply reflected in its specialized language. These mining terms, from “Adit” to “Mother Lode,” encapsulate centuries of human endeavor, technological innovation, and geological understanding. They narrate the arduous journey of extracting valuable resources from the earth, detailing the challenges faced by prospectors and the ingenious methods developed to overcome them. For historians, geologists, and enthusiasts alike, mastering this lexicon of mining terminology offers a profound appreciation for the rich legacy and ongoing significance of the mining industry in shaping economies and societies worldwide. This glossary serves as a foundational guide to understanding the enduring impact of mineral extraction.
