Glossary of Mining Terms
The world of mining, particularly during the bustling eras of westward expansion and resource extraction, developed its own unique vocabulary. This lexicon, born from the hard labor, technological innovation, and the pursuit of precious minerals, paints a vivid picture of the mining landscape. This glossary serves as a guide to understanding the terminology used by miners, geologists, and others involved in the extraction of valuable resources from the earth. It illuminates the techniques, tools, and geological formations that defined the mining industry, offering a glimpse into a fascinating chapter of history.
A
Adit: An adit is essentially a horizontal tunnel driven into the side of a hill or mountain to access a mine. Unlike a shaft, which is vertical, an adit provides a direct, level entrance, facilitating the removal of ore and providing ventilation and drainage. Imagine miners pushing ore carts directly out of the mountainside – that’s the purpose of an adit. The image above shows an adit at the Lucky Tiger Mine, Humboldt County, Nevada.
Alluvial or Bench Deposits: These are ancient river-washed deposits of rock and gravel, often located far from any existing water source. Over geological timescales, rivers change course, leaving behind these elevated "bench" deposits. They are particularly interesting to miners because they often contain untapped gold potential, having never been previously worked. Hydraulic mining techniques were often employed to exploit these alluvial deposits.
Alluvium: This term refers to a deposit of loose gravel, sand, silt, and clay that lies between the topsoil and the bedrock. It’s the material transported and deposited by flowing water.
Amalgam: An amalgam is a mixture of gold or silver with mercury (quicksilver). The mercury acts like a magnet, attracting and binding to the precious metals.
Amalgamation: Amalgamation is the process of using mercury to extract fine gold particles from crushed ore. The mercury forms an amalgam with the gold, which can then be separated from the waste material. The gold is then recovered by heating the amalgam, which vaporizes the mercury, leaving the gold behind.
Ancient Riverbed Claims: These are claims located in the beds of rivers that no longer exist. These ancient riverbed claims represent potentially rich sources of gold that were deposited over millennia.
Arastra: An arastra is a primitive mill used to grind ore. It consists of one or more large stones dragged around a circular bed, crushing the ore into a fine powder for further processing. These were often used in the early days of mining before more sophisticated equipment was available.
Argentiferous: This term describes a substance that contains silver. Argentiferous ores are mined for their silver content.
Assaying: Assaying is the process of determining the proportion of a specific metal, such as gold or silver, in a sample of ore or bullion. Assaying is crucial for evaluating the value of a mining claim or a batch of refined metal.
Assessment: In mining, assessment refers to the amount of money or labor required to maintain a mining claim. Claimholders must perform a certain amount of work or pay a fee to retain their rights to the claim.
B
Bar Claims: Bar claims are found in low-lying accumulations of sand and gravel in rivers, exposed during periods of low water. These areas are often targeted by prospectors using pans and sluice boxes.
Barren Contract: A barren contract describes a section of a vein that contains no valuable minerals. This is a disappointing discovery for miners working under a contract.
Base Bullion: Base bullion refers to precious metals, such as gold or silver, that are contained within lead. The lead acts as a carrier metal, and the precious metals are later extracted through refining processes.
Bedrock: Bedrock is the solid rock formation that underlies the "pay dirt" or mineral-bearing material. Finding bedrock is often a key goal in placer mining, as heavier minerals tend to concentrate on the surface of the bedrock.
Bench Claims: Similar to alluvial deposits, bench claims refer to mineral deposits found on narrow, elevated terraces on hillsides above a river. These areas represent former riverbeds that have been uplifted over time.
Blende: Blende is an ore of zinc, consisting of zinc and sulfur.
Blind Lode: A blind lode is a vein of ore that does not outcrop on the surface. Finding a blind lode requires geological expertise and exploration techniques.
Blossom Rock: Blossom rock refers to loose pieces of ore found on the surface or near where a vein outcrops. It’s detached from the main vein but indicates its presence.
Bonanza: A bonanza is a rich and profitable ore deposit. The term, derived from Spanish meaning "good luck," signifies a significant discovery that brings wealth to the miner.
Breasting Ore: Breasting ore refers to the process of extracting ore directly from the face or end of a tunnel.
Bucket Line Dredge: Unlike modern suction dredges, bucket line dredges were massive machines that used a series of buckets to scoop up water and gravel and run it through a long sluice box.
C
Cage: The cage is the elevator used in a mine shaft to hoist and lower ore cars, miners, and equipment.
Cap Rock: Cap rock is the layer of rock that overlays an ore deposit or vein.
Carbonate: Carbonate refers to a geological formation containing silver ore with a lead content of 5 to 70 percent.
Carboniferous: Carboniferous describes a geological formation containing coal.
Chilean Mill: Similar to the arastra, a Chilean mill is a machine that uses heavy stone wheels rotating around a central shaft to crush ore.
Chlorides: Chlorides are compounds of chlorine and silver.
Chute: A chute is an inclined channel through which ore slides down, often used to transport ore from higher levels in a mine to lower levels or to the surface. The image above shows a large chute at the Kennecott Copper Mine in Alaska.
Chopping: Chopping refers to the rock visible on the surface that indicates the presence of a lode or vein beneath.
Claim: A claim is a parcel of land, typically 25 to 300 feet wide and 1,500 feet long, that is granted to an individual or company who discovers minerals within its boundaries. The claim grants the holder the right to mine and extract those minerals.
Conglomerate: A conglomerate is a sedimentary rock composed of gravel and pebbles cemented together.
Contact: Contact refers to the boundary or junction between two different types of rock, such as porphyry and slate.
Contact Vein: A contact vein is a vein of ore that occurs along the contact plane between two dissimilar rock masses.
Cord of Ore: A cord of ore is a measurement of 128 cubic feet of broken ore, which is roughly equivalent to seven tons of quartz rock.
Cornish Pump: A Cornish pump is a type of water pump developed in Cornwall, England, and commonly used in 19th-century deep mines to remove underground water.
Crosscut: A crosscut is a horizontal tunnel driven perpendicular to the main direction of a vein or lode.
Country Rock: Country rock is the rock that surrounds a vein or lode, usually barren of valuable minerals.
Coyote: Coyote mining involves tunneling into river-borne gravel to reach bedrock, where rich mineral deposits are often found.
Crevice: A crevice is a narrow opening or crack in rock.
Cribbing: Cribbing refers to the timber or plank lining of a shaft, used to support the walls and prevent collapse.
CrossCut: A CrossCut is a level driven across the course of a vein.
Cupriferous: Cupriferous describes a substance that contains copper.
D
Debris: In mining, debris refers to sediment and waste material generated from mining operations.
Denudation: Denudation is the process of rocks being exposed by running water or other erosional forces.
Deposit: A deposit is a body of ore that is distinct from a lode or vein.
Diggings: Diggings is a general term for placer mining operations in progress.
Diluvium: Diluvium refers to a deposit of superficial sand, loam, gravel, and pebbles.
Dip: Dip refers to the angle or slope of a vein relative to the horizontal plane.
Dredge: A dredge is a piece of mining equipment used to suck up dirt and gravel from a stream bed using water pressure.
Drift: A drift is a horizontal underground passage excavated along a rich ore vein in hard rock mining.
Dry Diggings: Dry diggings refers to earth that is excavated during the summer months and stored for washing during the winter when water is more plentiful.
Dry Washing: Dry washing is a method of separating gold from soil in arid regions by using wind to blow away the lighter soil particles.
Drywasher: A drywasher is a desert mining tool that uses wind to separate gold from other materials, similar to a high banker but without water.
Dump: A dump is a pile of ore or debris removed from a mine or tailings from sluicing operations.
E
End Lines: End lines are the lines that define the boundaries at the ends of a mining claim.
F
Face: The face is the end of a level or tunnel where mining is actively taking place.
Fathom: A fathom is a unit of measurement equal to six feet, often used to describe the dimensions of a vein.
Feeder: A feeder is a small vein that joins a larger vein.
Feldspar: Feldspar is a group of crystalline minerals consisting of aluminum silicates with potassium, sodium, calcium, or barium, an essential component of nearly all crystalline rocks.
Fissure Vein: A fissure vein is a crack or fissure in the earth’s crust that has been filled with mineral matter.
Flat Claims: Flat claims are mineral deposits found on relatively flat surfaces.
Flour Gold/Gold Dust: Flour gold is gold that is so fine it resembles flour or dust.
Float: Float refers to loose rock or isolated masses of ore that have become detached from the original formation.
Flume: A flume is a channel or trough, often made of wood, used to carry water. Unlike sluice boxes, flumes don’t have riffles and are solely for water transportation. The image above shows a ten-mile long flume in Twin Springs, ID.
Flux: Flux refers to the flow of ore in a smelter furnace.
Footwall: The footwall is the layer of rock immediately beneath a vein.
Forfeiture: Forfeiture refers to the loss of a mining claim due to failure to comply with regulations regarding the amount of work required.
Free Gold: Free gold is gold that is easily separated from quartz or dirt.
G
Galena: Galena is a lead ore consisting of sulfur and lead.
Gangue: Gangue is the worthless rock or mineral material that surrounds valuable metals in a vein.
Gash Vein: A gash vein is a vein that is wide at the top and narrow at the bottom.
Geode: A geode is a rounded rock containing a cavity that is lined with crystals or mineral matter.
Geology: Geology is the scientific study of the earth’s rocks and their formation.
Grizzly: A grizzly is a set of bars used in a flume to strain out large stones during hydraulic mining.
Gulch: A gulch is a small, narrow ravine.
Gulch Claims: Gulch claims are mineral deposits found in gullies that are typically dry for part of the year.
H
Hanging Wall: The hanging wall is the layer of rock or wall that lies above a lode.
Hard Rock Mine: A hard rock mine is a tunnel dug into solid rock to extract valuable rocks, minerals, or metals.
Heading: The heading is the vein above the drift.
Headings: In placer mining, headings refer to the mass of gravel above the head of a sluice.
Highbanker: A highbanker is a mobile sluice box that uses a pump to transport water and minerals to a different location.
High-Grade Ore: High-grade ore contains more than 20 ounces of silver per ton, with a lead content of 50 percent or more.
High Grading: High grading refers to the act of stealing valuable nuggets from sluice boxes.
Hill Claims: Hill claims are mineral deposits found in or under a hill.
Horse: A horse is a mass of rock that occurs within a vein.
Hydraulic Claims: Hydraulic claims are claims that are worked using hydraulic power.
Hydraulic “Giant” or Monitor: The hydraulic “giant” or monitor is a large nozzle that sprays vast amounts of water onto hillsides to recover gold. The image above shows hydraulic mining in Twin Springs, Idaho.
I
Inch of Water: An inch of water is a unit of measurement roughly equal to two and a half cubic feet per minute, referring to the amount of water that flows through a one-inch square opening.
Incline: An incline is a slanting shaft in a mine.
J
Jumping a Claim: Jumping a claim is the act of illegally relocating a claim on which the required work has not been done.
K
Knife Claims: Knife claims are minerals that are dug from crevices using a knife or spoon.
Kibble: A kibble is an iron Cornish bucket used to hoist ore and miners to the surface.
L
Level: A level is a tunnel cut on the vein from the main tunnel, also known as a drift.
Ledge: A ledge is a vein or lode.
Little Giant: A little giant is a movable nozzle attached to hydraulic pipes.
Locate: To locate means to establish possessory rights to a mining claim.
Lode: A lode is a metallic vein.
Long Tom: A long tom is a type of sluice box that is longer and narrower than a standard sluice box.
Low-grade Ore: Low-grade ore contains less than 20 ounces of silver per ton, with a lead content of 50 percent.
M
Metamorphism: Metamorphism is a significant change in the composition of rock due to pressure, heat, and water, resulting in a more compact and crystalline state.
Mill Run: A mill run is a test of the quality of ore after it has been processed in a mill.
Mineral: A mineral is a naturally occurring, homogeneous substance with a specific chemical composition and crystal structure. Minerals may or may not have economic value.
Mother Lode: The mother lode is the primary source of gold, often found in veins of quartz within mountainsides.
O
Open Pit Mine: An open pit mine is a mine that is excavated from the surface downward, rather than through tunnels.
Ore: Ore is a natural combination of minerals from which a metal or metals can be profitably extracted.
Outcrop: An outcrop is the portion of a vein that is visible at the surface.
P
Pack Train: A pack train is a group of horses or mules used to transport supplies to miners and loggers.
Pan or Panning: Panning is the process of using a pan, typically a shallow dish, to wash dirt and separate free gold. The image above shows gold panning in Pinos Altos, New Mexico.
Patch: A patch is a small placer claim.
Petering or Peter Out: Petering out describes the situation when an ore deposit begins to diminish or disappear.
Pitch: Pitch is synonymous with dip, referring to the angle of a vein.
Piping: Piping is the process of washing gravel in a hydraulic claim by directing water through a nozzle.
Placer: Placer refers to gold embedded in clay, sand, and gravel, encompassing all mineral deposits except veins. These claims are mined using water-based methods.
Pocket: A pocket is a cavity filled with ore or a rich deposit of precious metal.
Porphyry: Porphyry is a rock with a compact base containing crystals of feldspar.
Primary or Primitive Rocks: Primary rocks include slate, quartz, serpentine, granite, and gneiss, the lowest group of rocks.
Prospecting: Prospecting is the act of searching for mineral lodes or placers.
Pulp: Pulp is pulverized ore in the lixiviation process.
Q
Quartz: Quartz is a hard, crystalline mineral that often encases metals.
R
Reducing: Reducing is the process of separating metals from foreign substances in ores.
Retort: A retort is a vessel used for distilling or decomposing substances by heat.
Riverbed Claims: Riverbed claims are mineral deposits found in river beds, accessed by diverting the river’s natural course.
Rocker Box or Cradle: A rocker box is a device similar to a sluice box, used in areas with limited water. It is rocked back and forth like a cradle while water is poured over the material.
S
Salting a Mine: Salting a mine is the fraudulent practice of placing minerals or ore in barren areas to deceive potential investors.
Shaft: A shaft is a vertical or inclined excavation for prospecting or working mines.
Shaker Table: A shaker table is a machine that uses vibration to separate minerals based on their density.
Side Lines: Side lines are the lines that bound the sides of a mining claim.
Slag: Slag is the waste material left as a residue after smelting metallic ore.
Slimes: Slimes are the finest particles of crushed ore and gangue from mills.
Sluice Box: A sluice box is a trough through which gold-bearing gravel is washed, using riffles to trap heavier gold particles.
Sluice Claims: Sluice claims are claims that are worked with sluices.
Smelting: Smelting is the process of reducing ores to metals in furnaces.
Soft Carbonate: Soft carbonate is a silver-bearing mineral that is easily extracted with a pick and shovel, often sand impregnated with carbonated or oxidized minerals.
Sourdough: A sourdough is an experienced miner who has prospected for many years.
Square Set: A square set is a set of timbers used for support in underground mining.
Stamp or Stamp Mill: Stamp mills are machines used for crushing ores. The image above shows the Panamint, California Stamp Mill.
Stope: A stope is a step-like excavation formed by removing ore around a mine shaft.
Stoping: Stoping is the act of breaking down a stope and excavating it with a pick.
Strata: Strata is a series of beds of rock.
Stull: Stulls are platforms of timbers between levels, used to strengthen the mine, store ore, and deposit waste material.
Stull Timbers: Stull timbers are large timbers placed across a vein or lode to support the walls.
Strike: A strike is a valuable mineral development made unexpectedly.
Sulphuret: A sulphuret is a combination of sulfur with a metallic, earthy, or alkaline base.
Sump or Sumph: A sump is a pit at the bottom of a mine to collect water.
T
Tailings: Tailings are the gravel, dirt, and rocks left behind after extracting the minerals. The image above shows miners in the Greenwater Mining District of California.
Tunnel: A tunnel is a level driven at right angles to the targeted mineral vein.
Tunnel Claims: Tunnel claims refer to gold-bearing earth removed from tunnels and subsequently washed.
V
Vein: A vein is an aggregation of mineral matter in fissures of rocks.
W
Walls: Walls are the sides next to the lode.
Wash: Wash is the first geological formation, composed of earth, sand, gravel, and other minerals, washed down from the mountains.
Waste: Waste is rock containing no ore but removed during mining operations.
Whim: A whim is a winding machine used for hoisting ore out of a shaft.
Windlass: A windlass is a device smaller than a whim, used to raise ore from a shaft.
Winze or Wizen: A winze is a shaft sunk from one level to another.