Mining Glossary Of Terms

Prospecting And Mining Glossary
The following is a glossary of mining terminology popular with old prospectors and modern miners.

Alphabetical Order Terms

ADIT -- A horizontal or inclined entrance into a mine.

ALCHEMY -- The forerunner of modern chemistry. Its chief aims were the transmuting of baser metals into gold, and the discovery of an elixir of life.

ALLOY -- When two or more metals are melted or joined together, an alloy is formed. This is done to harden or strengthen other metals, such as silver added to gold; or to form a metal not found in nature, e.g., copper and zinc to form brass. Alloys have different properties from their constituent elements; e.g., they are poorer conductors of heat and electricity, often harder, and, with the exception of aluminum alloys, more resistant to corrosion.

ALLUVIAL MINING -- The practice of working a natural alluvial fan where centuries of erosions has washed down great mountains into wide, sloping deposits of loosely packed dirt, stones, gravel and boulders. (See also Deposits)

AMALGAMATION -- This is a mining term relating to the combination of metal such as silver, platinum or gold, with mercury. Amalgamation is one of the simplest and easiest ways of recovering fine gold from concentrates.

ANALYSIS (See Assay)

ANCIENT STREAMBED -- Due to landslides, earth tremors and other natural forces, the course of a river was often dammed and forced to seek alternate routes. These "old channels", or ancient riverbeds are eagerly sought by prospectors, as their gold-bearing gravels have never been touched.

ANNEAL -- The process of heating, then cooling slowly, for the purpose of making metals less brittle.

APRON -- The burlap or canvas apron is the part of the rocker that is stretched across a frame, at an incline, beneath the hopper. It traps the fine particles of gold as they fall through the perforated holes of the hopper's bottom.

AQUA REGIA -- A mixture containing one part nitric acid to four parts of hydrochloric acid which is strong enough to dissolve gold and platinum.

ASSAY -- The evaluation or analysis of ore to determine the proportion of gold, silver or other valuable metals. Usually an assay is done by chemical methods and was fairly accurate.

ASSIMILATE -- This is the ability of mercury to absorb gold, silver or platinum into a common ball, or alloy, called amalgam, while ignoring lighter sands and gravel.

AURIFEROUS QUARTZ MINING --These are mines where the production of gold is the main ore, not a by product.

AVOIRDUPOIS WEIGHT -- This refers to the common English and American system of weight measure. This system is not used for medicine, gold or other precious minerals.

437 Omega=1 ounce

7000 grains=16 ounces

16 ounces=1 pound

BAKED POTATO METHOD -- A method of separating gold from the amalgam.

BAR -- This term was given to submerged sandbars that formed in a creek or river. It increased in size as dirt, sand, gravel, black sands and gold were deposited. Sandbars have produced great quantities of gold in the past and should not be overlooked today, if you employ equipment which can wash it rapidly.

BARREN -- An area of a river or stream that is incapable of producing gold, or produces exceedingly little.

BASE-METAL MINING -- This is the mining of metals such as copper, lead, zinc, tin, aluminum, etc., as opposed to precious metals such as silver, gold or platinum.

BATTERY -- Another name for a stamp mill.

BEDROCK -- Originally, this referred to the solid rock bottom of a stream or river. A false bedrock is formed when the feldspar portion of eroded rocks gathers and settles. creating a tough clay or cemented-gravel. The largest quantities of gold are generally recovered within a couple of feet above bedrock.

BENCHES -- A flat area above a stream or river.

BLACK SAND -- Usually composed of hematite and magnetite, black sands are heavier than ordinary sands and settle much in the same manner as does gold. For this reason, black sands are good indicators of gold and should never be overlooked. When panning, black sands will normally comprise most of the concentrates remaining in the pan.

BONANZA -- This is a term used to describe an exceptionally rich and persistent vein of ore, usually gold.

BULLION -- A term used to describe raw gold or silver that is ready to be shipped to the mint. When the metal has been reduced to nearly pure form, it is then cast into bars or ingots for easy storage and shipping. Occasionally other forms were used. The famed Bullion Mine in the Cariboo once melted one big clean-up into the form of a large naval gunshell. It weighed 650 lbs. and was valued at $178,000.

BYPRODUCT -- A secondary product obtained while mining something else. For example, gold is often a byproduct of a copper mining operation, which means copper is the main metal mined, but some gold is also recovered.

CACHE -- This was a temporary hiding place for gold or other wealth, including supplies, food or equipment. Basically, anything hidden by the owner until his return.

CALAVERITE -- A gold ore with a whitish, metallic luster composed of gold in combination with tellurium.

CARAT -- A measure of weight for gold or precious gems. Pure gold is 24 carats.

CELESTIALS -- An expression used to describe Chinese miners. The term was in wide-spread use during the California gold rush, and was brought into British Columbia when the Forty-Niners came north. The word originated from the Celestial Empire of China.

CEMENTED-GRAVEL -- A hard, tightly-packed material that is frequently rich in gold. It can accumulate and form a false bedrock.

CHAMOIS -- A kind of soft leather used to squeeze out the mercury from the amalgam before burning.

CHINA DIGGINGS -- A term used to describe an area which was abandoned as unprofitable, but was still being worked by the Chinese. Some of these often proved to be far richer than thought.

CLAIM JUMPER -- Someone who seizes, or illegally restakes a claim which has already been filed by another prospector.

CLAIM -- An area that has been filed with the proper government agency for the extraction of gold or other metals. It gave the prospector the rights to the minerals within his claim for a certain period of time. The boundaries of the claim were marked by stakes, piles of rocks, etc. A can containing the description and particulars of the claim was usually placed on or near one of the posts.

CLAY (See Cemented-Gravel)

CLEAN-UP -- A term used to describe the cleaning-up of concentrates from the riffles of rockers, sluices, dredges, etc., after the gold-bearing gravel has been washed. These concentrates are then processed, usually through amalgamation, to recover the gold.

COARSE GOLD -- Rough, unrefined nuggets of gold which vary in size. Gold that has travelled a considerable distance is usually worn smooth; therefore, coarse gold is an indication of limited travel.

COLOR --A term used to describe the minute specs of gold in gravel. Colors, though themselves minuscule, are indicators of gold in a particular stream or river.

CONCENTRATES -- This is the name given to the material that remains in the gold pan, rocker, sluice, etc., after washing. Concentrates are usually composed of black sands, gold and silver, but particles of platinum and a variety of other minerals could be included.

CONDUIT -- A channel or pipe used for conveying water.

CORE DRILL -- These are usually core samples extracted from solid rock to test for mineral content without blasting away tons of rock.

CREVICE -- A crack or narrow fissure in bedrock which tends to accumulate and trap gold. Small cracks can hold large quantities of gold, and are usually the best prospects for the gold panner.

DEAD WORK -- This phrase was used by prospectors to describe the work of clearing away over-burden to get at the gold-bearing gravel.

DEPOSITS -- This usually refers to an area where gold or other metal has been found. There are two types of placer deposits; eluvial deposits, located near the originating lode; and alluvial deposits, found at considerable distances from the originating lode.

DIGGINGS -- This name usually applied to claims that were currently being worked for gold, silver, or other ore.

DISCOVERY CLAIM -- This was the first claim filed on a given stream or river. The other claims were then staked above and below the discovery claim, which was legally larger than any other claim on the creek.

DREDGE -- A dredge is a machine used for scooping or sucking goldbearing gravel from the riverbed. There are numerous types and sizes, ranging from the small, portable, compact models that can easily be operated by one man, to large barge-type dredges for clearing mud from harbour entrances. Next to hydraulic mining, nothing destroys the landscape faster than dredges.

DRIFT -- "Drift" mining simply means tunnelling a horizontal shaft that leads from a central deposit or ore. Drifts can run for hundreds, even thousands of feet, as miners traced tiny seams of gold fanning out from the original strike.

DRY PLACER -- A deposit of gold or precious metal found on dry ground.

DRY WASHER -- This is a device used to work claims without the use of water. Instead, a small billows blows away the light materials, leaving the gold and heavy particles to be panned later.

DUCTILITY -- The ability of metals to be drawn out in fine wires without breaking.

DUST -- This term refers to particles of gold so minute that they resemble dust. In the old days, the amount of gold dust a miner could pinch between his thumb and forefinger constituted one dollar, while a whisky glass full was worth $100.00.

EL DORADO -- Originally derived from the Spanish, referring to a legend about a land of gold and plenty. It is now used frequently to describe a place of fabulous wealth, a region abounding in gold and precious gems.

ELECTRUM -- An alloy of gold and silver.

FELDSPAR -- A constituent of granite, basalt, and other igneous rocks that form a large part of the earth's crust. Clay is the chief substance formed when weathering decomposes feldspars. (See also Bedrock)

FINE GOLD -- Generally, this term refers to gold which can pass through a 40-mesh screen. It includes fine gold and dust, which, in your pan, will appear as colour so small that it can only be collected by amalgamation.

FINENESS -- This is a word used to indicate the purity of gold.

FLAKE GOLD -- These are small chips of gold, or pieces that have been flattened in transit.

FLAT -- A word describing a level spot, often near a stream or river, that was suitable for a settlement.

FLOATATION PROCESS -- A method for recovering gold from crushed ore and concentrates.

FLOUR GOLD -- An extremely fine gold that is difficult to save. It is uneconomical to pan flour gold because of its almost powdery, size and weight.

FOOL'S GOLD -- (See Pyrite)

FLUME -- An inclined waterway, most often a channel dug in the hillside to transport water to hydraulic mining camps. Simply described, they are similar to a long series of sluices, and in fact, the name flume was once synonymous with sluice.

FRACTION -- A small portion of ground lying between two claims which could not be staked by either as it exceeded their legal limits. "Twelve-foot" Davis , was so named after a 12-foot fraction on Williams Creek which he worked between two other claims. After recovering over $12,000, Davis sold the fraction, which then yielded over $100,000.

FULMINATE OF MERCURY -- An explosive substance made by dissolving mercury in nitric acid and adding alcohol.

GANGUE -- The worthless minerals associated with metal ore deposits.

GEOLOGY -- The science of the rocks and strata of the earth's crust.

GIANT MONITOR -- An apparatus fitted with a nozzle used in hydraulic mining. Water is forced through the nozzle under great pressure, then directed against gold-bearing gravel. The material is then washed into sluices where the gold can be separated.

GLORY HOLE -- A term used by miners to describe a small, but unusually rich deposit of gold.

GOLD BEATER -- Someone who beats gold into thin sheets.

GOLD LEAF -- Gold beaten into extremely thin sheets.

GOLD RUSH -- The wild scramble by prospectors to reach the new goldfields.

GRADIENT -- The slope or descent of a stream or river.

GRAIN -- This term is used to describe small particles of gold, and is also used as a unit of weight. (See Avoidupois and Troy Weights)

GRAVEL -- The gold-bearing material in a stream which you must wash to recover gold.

GRIZZLY -- A device used to keep rocks and boulders out of a sluice box.

HALF-LIFE -- The rate of decay of radioactive materials.

HALOGENS -- Any member of the family of very active elements consisting of fluorine, chlorine, bromine, and iodine. Chemically the hologens resemble one another closely and form a saline compound by simple combination with a metal.

HARDROCK MINING -- This usually refers to quartz mining and is said to have originated in California about 1850. First a main shaft had to be sunk, then horizontal shafts or drifts would be cut that followed the various seams of gold as it led from the main deposit. As this type of mining required a sizable investment, the small operator was quickly eliminated.

HARDPAN (See Cemented-Gravel)

HEAD FRAME -- This applied to the heavy timber frame found above most hardrock mine sites. It was used to hoist ore from the depths of the mine, and also as an elevator to hoist and lower workmen.

HEMATITE -- A form of native iron ore, blood-red in color. (See Black Sand).

HIDDEN VALUE -- The unseen values usually found in black sands, which in many cases, could not be detected by the naked eye.

HOPPER -- The tray in the upper end of a rocker.

HYDRAULIC MINING -- In hydraulic mining, water under great pressure was discharged through monitors against a gold-bearing hillside. The force of the water would wash away the hillside, flushing the silt and gravel through sluices where it could be separated and the gold recovered. Hydraulicking could-and often did-completely ruin the landscape.

HYDROCHLORIC ACID -- The only known compound of hydrogen and chlorine made by dissolving the corrosive gaseous compound, hydrogen chlorine, in water. (See also Aqua Regia).

INGOT -- A metal bar, especially of silver or gold, usually cast from a mold for convenience in handling and measuring.

IRIDIUM -- A silvery metallic element belonging to the platinum group.

JADE -- A very hard, semi-precious stone, usually dark green in color, that is carved for ornaments or used in jewelry. Frequently found in British Columbia .

JIGA -- partly or fully watersubmerged screen that is shaken to wash or sort particles by weight and size. Also called jigger.

LODE --A metallic vein in the earth's crust, especially silver or gold. These lodes were the original source of placer gold.

LONG TOM -- This was a special sluice box of extra length so that it could capture extra fine particles of gold.

LOW GRADE -- Deposits of gold, silver, or other metals, which exist in insufficient quantities to be worked economically, except through large-scale methods.

MAGNETITE -- A magnetic form of iron ore also known as lodestone. (See Black Sand).

MALLEABLE -- The ability of a metal to be hammered without breaking.

MARCASITE -- A white iron pyrite used in jewelry because of its brilliance.

MERCURY -- A heavy, liquid metal, silvery-white in colour, with a very low melting point. Used to recover gold, silver and platinum from concentrates. Also called Quicksilver.

METALLURGY -- The art of working metals or of obtaining metals from ores.

MONITOR (See Giant monitor)

MOSS -- Small, thickly growing, cryptogamous plant which thrives on moist surfaces. Gold often accumulates in moss, which should be broken up and panned carefully before discarding.

MOTHER LODE -- A vein or streak of gold or other precious metal in the earth's crust from which placer deposits originate.

NITRIC ACID -- A highly corrosive, colorless liquid that emits choking fumes into air. A diluted solution is used to clean the gold-bearing concentrates before amalgamation, and also to clean mercury that has become dirty. (See Aqua Regia).

NOBLE METALS -- Metals which do not have great chemical activity, particularly gold, which is neither corroded by moisture nor affected by oxygen or ordinary acids.

NOVICE -- An amateur or inexperienced prospector or miner.

NUGGET -- A rough lump or mass of native gold of no particular size. These range in size from the head of a match to nearly 200 pounds. The largest United States nugget,

OIL -- The preservative coating which must be burned off steel gold pans before using.

OLD CHANNEL (See Ancient Streambed)

ORE -- Rock containing metals or their compounds in sufficient quantities to be mined.

OUNCE A DAY -- In the early days, ground that yielded an ounce of gold a day, through panning, was considered rich ground.

OUTCROP -- The point where the vein or lode of a metal comes to the surface of the earth's crust and is visible.

OVERBURDEN -- Generally, the low-grade material which must be first cleared away to get at the rich gold-bea ring gravel just above bedrock.

PALLADIUM -- A rare metal of the platinum group.

PAN -- A broad shallow vessel of metal or plastic used to wash gold-bearing gravel.

PANNING -- The act of washing gold-bearing gravel with a gold pan, batea, or other similar vessel.

PAY -- A word used to describe gold-bearing gravel that returns wages or better to the miner.

PAYDIRT -- This is a term used to describe an area where a prospector has found gold, e.g., "struck paydirt."

PENNYWEIGHT -- A Troy weight of 24 grains. (See Troy Weights)

PETER OUT -- A common expression that applied to a claim, mine, or deposit that had been thoroughly worked over, leaving only the worthless rubble behind.

PLACER -- Generally, this word refers to deposits of gold-bearing gravel. (See Deposits)

PLACER MINING -- The act of recovering gold from placer deposits by means of a gold pan, rocker, sluice, dredge, etc. Placer mining depends largely on water for washing and separating the gold and gravel.

PLATINUM -- A rare, silvery-white malleable metal. It is harder than gold, but very ductile. In B.C. it was discovered in the Similkameen region, but was discarded as worthless by all except the Chinese.

PLAYED-OUT (See Peter-Out)

POCKET -- An unusually large concentration of gold in a small area was often referred to as a pocket". (See also Glory Hole)

POKE -- A small leather bag or pouch, usually two inches wide and six inches deep, with a drawstring at the top. These were used as wallets by miners to carry gold dust and nuggets.

POORMAN'S DIGGINGS -- This term did not mean that the area being worked was low grade or yielding small quantities of gold, but rather that it could be worked by a miner with a rocker or sluice with very little capital. Hence, it could be worked by a poor man.

POT HOLE -- A cavity formed in bedrock by the action of stones in the eddy of a stream. They are highly overrated as gold producers, as the gold is eventually ground into fine dust and escapes.

PRODUCTION -- The total yield or "production" of gold or other precious metal from a mine, claim or deposit.

PROSPECTING -- The act of searching for gold, silver, copper, lead, or any other valuable metal. In the case of placer gold deposits, the prospector retrieves the gold as he finds it, thus becoming a miner. If lodes or low-grade metals are located, the prospector usually sells or leases the rights to them to a large mining company which has the necessary equipment and resources to mine them, and he continues looking, or "prospecting," for new finds.

PUDDLING BOX -- A box used to break up tough clay or cementedgravel.

PYRITE -- A name for many compounds of metals with sulpher or arsenic, especially iron pyrites or copper pyrites. Pyrite is brassyellow and brittle, but because of its color, is often mistaken for gold, hence the name "fool's gold."

QUARTZ -- One of the most common materials found in the mother lode. It consists of pure silica or silicon dioxide and is formed in massive and in hexagonal crystals. Quartz may be transparent, translucent, opaque, colourless or coloured. Most of the hardrock mining done for gold comes from quartz veins.


REAGENT -- Any substance, generally in a solution, employed to bring about a characteristic reaction in a chemical analysis.

RECOVERY -- The act of "recovering" fine gold from the heavy concentrates, usually through amalgamation.

REFINE -- To reduce crude metals to a finer, purer state.

RETORT -- An apparatus used to separate an amalgam of gold and mercury, through heating, which saves the mercury for future use.

RHODIUM -- A hard, silver-white metallic element found in river sands or rocks associated with other members of the platinum family to which it belongs.

RICH -- Ground where gold or other precious metals abound.

RIDDLE -- A large perforated iron sheet which forms the bottom of the hopper in a rocker, used for sifting or screening gravel. (See diagram and description on page 60).

RIFFLES -- Simply stated, these are obstructions which line the bottom of a rocker, sluice or dredge, collecting the fine gold. Different types of riffles include; common riffles, zig-zag riffles, block riffles, stone riffles, poles riffles, etc. (See diagrams and description on pages 62 & 63).

RIM -- The outer border or edge of a gold pan.

ROCKER -- A device consisting of a box which rests on "rockers," and which is used to wash placer deposits. (See diagram and description on page 60).

SKIM -- The practice of removing the froth from the surface during the floatation method of recovering gold.

SLOPE -- The gradient of a stream or terrain.

SLUICE BOX -- The sluice was invented by a party of Nevada miners in 1850. It consisted of a long trough leading down from their claim to their Long Tom. The sluice was an immediate success, becoming a standard tool of the California gold rush, and was later brought north into Canada .

SLUICING -- The act of washing gold from river gravel through the use of a sluice box.

SNIPING -- In miner's jargon, this word meant the act of prospecting and re-working old claims, dumps, and other sites that have been abandoned. It also refers to cleaning out bedrock cracks.

STAKE -- This could refer to the act of "staking" a legal claim by following the necessary regulations (See Claim), or it could refer to the occasions when a miner had accumulated enough gold to retire, either temporarily or permanently. In the latter case, the miner is said to have "made a stake."

STAMP MILL -- A piece of heavy machinery that is power-operated and smashes the hardrock ore into a powder so that it can be processed for gold or other precious metals.

STRIKE -- This usually denoted the discovery of gold or silver. Once a ',strike", or discovery had been made, hundreds, or even thousands, would swarm into the area.


TAILING -- This word describes the waste material that is left or discarded after the gold is removed. Also called dumps, these are generally piles or rocks or debris left from the mining operation. Once considered worthless, tailings have become a target for modern prospectors. Occasionally large nuggets were discarded with the stones; or valuable metals, unknown to early prospectors, were tossed aside.

TAILING WHEELS -- These were wheels used to transport the waste material from the mines to a place some distance away.


TRAY (See Hopper]

TRESTLE -- In mining a trestle is a wooden frame consisting of braced legs fixed underneath horizontal bars, used to support
a sluice or series of sluices.

TRIBUTARY -- A branch of a stream flowing into a larger stream.

TROUGH -- A long, open vessel carrying water and gold-bearing gravel.

TROY WEIGHT -- A system of weight measurement for precious gems and metals. This system is different from avoir dupois weight with which most of us are familiar.

24 grains=1 pennyweight

20 pennyweights=1 troy ounce

12 troy ounces=1 troy pound

UNALLOYED -- A metal in the pure state, not alloyed with any other metal.

UNDERCURRENT -- A current under the surface of the main stream, sometimes flowing in a contrary direction.

UNPRODUCTIVE -- A mine or stream that was abandoned because it was unprofitable to work. Due to the recent escalation in the price of gold, many of these abandoned areas are being reopened.

WASHING -- Any material that is considered worthless after the gold has been removed. (See Tailing)

WEATHERED -- A term meaning well-worn, generally referring to bedrock, and a result of glacial and water action.

WET PLACER -- A deposit of gold or other precious metal located under water.

WELCOME STRANGER NUGGET -- An enormous nugget of gold weighing 2,280 ounces and yielding 2,248 ounces of gold.

WHEEL -- This refers to a variety of water-wheels employed to provide water for mining. These were put to effective use on the Fraser river.

WING-DAM -- This was a dam that divided a riverbed miners wanted to work, lengthwise, allowing water to flow through sluice boxes and other devices set up to wash the gravel. These were put effective use on the Fraser River .

WORKED OUT (See Peter out)


Geology Glassary
The following is a glossary of geological terminology

Alphabetical Order Terms

abyssal plain -- The ocean floor offshore from the continental margin, usually very flat with a slight slope.

accrete -- v. To add terranes (small land masses or pieces of crust) to another, usually larger, land mass.

alkaline -- Term pertaining to a highly basic, as opposed to acidic, subtance. For example, hydroxide or carbonate of sodium or potassium.

allochthonous -- Refers to something formed elswhere than its present location. Antonym of autochthonous.

alluvial fan -- n. A fan-shaped deposit of sand, mud, etc. formed by a stream where its velocity has slowed, such as at the mouth of a ravine or at the foot of a mountain.

alluvium -- n. a deposit of sand, mud, etc., formed by flowing water; alluvial - adj.

amber -- Fossilization where the organism is entrapped in resin and preserved whole.

andesite -- Igneous volcanic rock, less mafic than basalt, but more mafic than dacite; rough volcanic equivalent of diorite.

anticline -- A fold of rock layers that is convex upwards. Antonym of syncline.

archipelago -- n. A group of islands; an expanse of water with scattered islands.

asphalt -- A dark bituminous substance found in natural beds. Residue from petroleum distillation.

autochthonous -- Refers to something formed in its present location. Antonym of allochthonous.

Banded Iron Formation -- n. Rock consisting of alternating light and dark layers of iron-rich chert (the dark layers have more iron minerals) formed from 3.8 to 1.7 billion years ago.

basalt -- Highly mafic igneous volcanic rock, typically fine-grained and dark in color; rough volcanic equivalent of gabbro.

basement rock -- n. The oldest rocks in a given area; a complex of metamorphic and igneous rocks that underlies the sedimentary deposits. Usually Precambrian or Paleozoic in age.

basin -- n. Any large depression in which sediments are deposited.

Basin and Range Province -- n. One of the most extensive systems of fault-bounded mountains separated by sediment-filled valleys, extending across Idaho, Oregon, Nevada, Utah, Arizona, New Mexico, California, and northern Mexico. Basin and Range topography The surface features typical of the Basin and Range Province.

bedrock -- n. The general term referring to the rock underlying other unconsolidated material, i.e. soil.

biostratigraphy -- n. The study of rock layers (e.g., distribution, environment of deposition, age) based on their fossils;

biostratigraphic- adj.

biostratinomy -- The study of what happens between the death of an organism and burial. Part of taphonomy.

bioturbation -- n. The disturbance of sediment by organisms, e.g. burrows, trails, or complete mixing.

blueschist -- Metamorphic rock formed under great pressures, but not so great temperatures.

brackish -- adj. Slightly salty.

calcareous -- adj. Term used to describe a structure, secreted by an organism, that consists of or contains calcium carbonate (CaCO3), e.g., the shell of a bivalve.

caldera -- n. A large circular volcanic depression, often originating due to collapse.

carbon film -- Thin layer of carbon remains of past life found in sedimentary rocks.

carbonate -- n. (adj.) A mineral composed mainly of calcium (Ca) and carbonate (CO3) ions, may also include magnesium (Mg), iron (Fe) and others; n. rock or sediments derived from debris of organic materials composed mainly of calcium and carbonate (e.g., shells, corals, etc.) or from the inorganic precipitation of calcium (and other ions) and carbonate from solution (seawater). For example, limestone or dolomite. carbonate platform – n. A broad (100s of meters), flat, shallow submarine expanse of carbonate rock, more common in the early-middle Paleozoic. carbonate bank – n. A narrow (10s of meters), fairly flat, shallow, submarine plateau of carbonate rock, more common from the middle-late Paleozoic to the present, e.g., the Bahama Banks.

casts -- Fossils formed when water containing minerals leaks into a mold. The minerals harden to form a copy of the original structure or organism.

chalk -- A soft compact calcite, CaCO3, with varying amounts of silica, quartz, feldspar, or other mineral impurities, generally gray-white or yellow-white and derived chiefly from fossil seashells.

chert -- Hard, dense sedimentary rock, composed of interlocking quartz crystals and possibly amorphous silica (opal). The origin of the silica is normally biological, from diatoms, radiolaria or sponge spicules. Synonymous with flint.

clast -- n. An individual grain or constituent of a rock; clastic- adj. Describes a rock or sediment composed mainly of fragments of preexisting rocks or minerals that have been transported some distance from their place of origin, e.g., sandstone, shale.

compactions -- Fossils that have undergone some degree of flattening of their three-dimensional structure.

compression -- Fossil formed when an organism is flattened (compressed) and a thin film of organic material from its body is left in the rock.

concretion -- n. A hard, rounded mass, commonly of silica, calcite, dolomite, iron oxide, pyrite, or gypsum, that formed within a rock from the precipitation of these minerals around a nucleus, such as a leaf, bone, shell, or fossil, and ranging in diameter from centimeters to meters.

conglomerate -- A coarse-grained sedimentary rock, with clasts larger than 2 mm.

continental crust -- The Earth's crust that includes both the continents and the continental shelves.

continental margin -- n. The ocean floor from the shore of continents to the abyssal plain.

continental rise -- n. Part of the continental margin; the ocean floor from the continental slope to the abyssal plain. The continental rise generally has a gentle slope and smooth topography.

continental shelf -- n. The part of the continental margin from the coastal shore to the continental slope; usually extending to a depth of about 200 meters and with a very slight slope, roughly 0.1 degrees; includes conetinental and oceanic sediments down to the ocean floor.

continental slope -- n. Part of the continental margin; the ocean floor from the continental shelf to the continental rise or oceanic trench. Usually to a depth of about 200 meters. The continental slope typically has a relatively steep grade, from 3 to 6 degrees.

copal -- Brittle aromatic yellow to red resins of recent or fossil origin, obtained from tropical trees.

coprolites -- Fossilized feces.

core -- That portion of the interior of the Earth that lies beneath the mantle, and goes all of the way to the center. The Earth's core is very dense, rich in iron and the source of the magnetic field.

craton -- n. A part of the Earth's crust that has attained stability and has been little deformed for a long period of time, refers only to continents; cratonic- adj.

cross-bedding -- (n) The arrangement of sedimentary beds tilted at different angles to each other, indicating that the beds were deposited by flowing wind or water.

crust -- n. The outermost layer of the Earth, varying in thickness from about 10 kilometers (6 miles) below the oceans, to 65 kilometers (about 40 miles) below the continents; represents less than 1 percent of the Earth's volume.

dacite -- Igneous volcanic rock, less mafic than andesite, typically fine-grained and light in color; rough volcanic equivalent of granodiorite.

delta -- n. A low, nearly flat accumulation of sediment deposited at the mouth of a river or stream, commonly triangular or fan-shaped; deltaic– adj.

dendrites -- n. Small branching patterns on rocks made of iron and manganese oxides that show the passage of fluids through the rock.

deposition -- Any accumulation of material, by mechanical settling from water or air, chemical precipitation, evaporation from solution, etc.

diagenesis -- All of the changes that occur to a fossil (or more generally any sediment) after initial burial; includes changes that result from chemical, physical as well as biological processes. The study of diagenesis is part of taphonomy.

diatomite -- Diatomite, or diatomaceous earth, is a siliceous sedimaentary rock formed from the accumulations of diatoms or other nanoplankton.

diorite -- Igneous plutonic rock, less mafic than gabbro, but more mafic than granite and granodiorite; rough plutonic equivalent of andesite.

dip -- The angle that a bedding plane or fault makes with the horizontal when measured perpendicular to the strike of the bedding plane or fault.

dolomite -- A carbonate sedimentary rock composed of more than 50 percent of the mineral calcium-magnesium carbonate (CaMg(CO3)2).

drill core -- n. A column of material (e.g., mud, ice, rock) removed from the earth by drilling. Often used as a tool for exploration of natural resources.

drumlin -- n. Elongated mound of glacial sediment deposited parallel to ice flow.

epicenter -- Point on the Earth's surface directly above the focus of an earthquake.

erosion -- n. The processes by which materials of the Earth's crust are worn away, loosened, or dissolved while being transported from their place of origin.

erratic -- n. A large, isolated boulder left behind by a glacier.

escarpment -- n. A steep or vertical cliff, either above or below sea level.

esker -- n. A ridge of glacial sediment deposited by a stream flowing in and under a melting glacier.

estuary -- n. An area where fresh water comes into contact with seawater, usually in a partly enclosed coastal body of water; a mix of fresh and salt water where the current of a stream meets the tides; estuarine– adj.

evaporite -- n. a deposit of salt minerals (e.g., halite, gypsum, anhydrite) left behind by the evaporation of seawater, usually forms within a restricted basin.

extrusive -- Igneous. Antonym of intrusive.

fault -- n. (v.) A fracture, or large crack, in the Earth's crust where one side moves up/down/sideways relative to the other; fault block- n. pieces of crust that have slipped into or alongside a fault; fault zone- n. an area with multiple faults.

felsic -- Term used to describe the amount of light-colored feldspar and silica minerals in an igneous rock. Complement of mafic.

focus -- The initial point within the Earth that ruptures in an earthquake, directly below the epicenter.

fold -- Bent rock strata.

fossil -- Any evidence of past life, including remains, traces, imprints as well as life history artifacts. Examples of artifacts include fossilized bird's nests, bee hives, etc.

fossil record -- All of the fossils that have existed throughout life’s history, whether they have been found or not.

fossiliferous -- adj. Rich in fossils.

freezing -- To preserve an organism without any significant alteration to its chemical composition by subjecting it to freezing temperatures.

gabbro -- Highly mafic igneous plutonic rock, typically dark in color; rough plutonic equivalent of basalt.

Gastroliths -- Fossilized gizzard stones, usually only applicable in the fossil study of reptiles

geologic maps -- Maps that show the types and ages of rock of an area. These maps are used by paleontologists to find areas that are likely to contain fossils they are interested in.

glass -- A non-crystaline rock that results from very rapid cooling of magma.

granite -- Highly felsic igneous plutonic rock, typically light in color; rough plutonic equivalent of rhyolite. Granite is actually quite rare in the U.S.; often the term is applied to any quartz-bearing plutonic rock.

granodiorite -- Igneous plutonic rock, less felsic than granite, typically light in color; rough plutonic equivalent of dacite.

graywacke -- Sandstone composed of poorly sorted angular clasts.


hydrothermal vent -- n. A place on the seafloor, generally associated with spreading centers, where warm to super-hot, mineral-rich water is released; may support a diverse community of organisms.

hypersaline -- adj. Extremely salty, having much more salt than normal seawater.

Ichnology -- The study of trace fossils.

igneous rock -- Any rock solidified from molten or partly molten material.

impressions -- Prints or marks made when an organism’s body has been compressed (flattened). Impressions are different from compressions because no thin organic material is left behind.

interbedded -- adj. Describes beds (layers) of rock lying between or alternating with beds of a different kind of rock.

intrusion -- n. Magma (and the rock it forms) that has pushed into pre-existing rock; intrusive- adj.; plutonic- syn. extrusive- ant.

island arc -- n. A curved chain of islands that rise from the sea floor, usually near a continent. The convex side usually faces the open ocean, while the concave side usually faces the continent, e.g., the Aleutian Islands in Alaska; volcanic arc- syn.

isotope -- One of two or more variations of the same chemical element, differing in the number of neutrons not the number of protons.

kame -- n. A short, steep-sided knoll of glacial sediment.

karst -- n. A type of topography formed by dissolution of rocks like limestone and gypsum that is characterized by sinkholes, caves, and subterranean passages.

kettle lakes -- n. Lakes formed as water fills a hole formerly occupied by a block of stranded ice.

lava -- Any molten material that is extrusive or volcanic, or the rock that forms from a molten extrusive.

limestone -- A carbonate sedimentary rock composed of more than 50 percent of the mineral calcium carbonate (CaCO3).

limy -- adj. Describes sediments, soils, or rocks that contain a significant amount of lime (calcium oxide, CaO).

loess -- n. A widespread, loose deposit consisting mainly of silt; most loess deposits formed during the Pleistocene as an accumulation of wind-blown dust carried from deserts, alluvial plains, or glacial deposits.

lowland -- n. (adj.) Large area of relatively low relief, usually applied to coastal regions that do not rise high above sea level. upland, highland – ant.

mafic -- Term used to describe the amount of dark-colored iron and magnesium minerals in an igneous rock. Complement of felsic.

magma -- n. Molten rock generated within the Earth; forms intrusive (solidifies below the surface) and extrusive (solidifies above the surface) igneous rocks.

mantle -- That portion of the interior of the Earth that lies between the crust and the core.

marine terrace -- n. A platform of marine deposits (typically sand, silt, gravel) sloping gently seaward. Such a platform may be exposed along the coast, forming cliffs, due to uplift and/or the lowering of sea level, e.g., Marine terraces of coastal Southern California.

marl -- n. A loose, crumbly deposit consisting of clay and calcium carbonate and formed in marine or freshwater conditions.

melange -- A body of rocks consisting of large blocks (mappable size) of different rocks jumbled together with little continuity of contacts.

metamorphic rock -- Any rock derived from other rocks by chemical, mineralogical and structural changes resulting from pressure, temperature or shearing stress.

metamorphism -- n. The process of altering the chemical or mineralogical composition of a rock through different amounts of heat and pressure below the surface of the Earth; metamorphose- v; metamorphic - adj.

microfossil -- n. A very small fossil, best studied with the aid of a microscope, e.g. foraminifera, radiolarians, and small vertebrate fossils such as teeth. macrofossil– ant.

mid-oceanic ridges -- Elongated rises on the ocean floor where basalt periodically erupts, forming new oceanic crust; similar to continental rift zones.

mineralization -- The process of replacing any organism’s original material with a mineral.

molds -- Fossils formed when the sediment surrounding a buried organism hardens. When the organism decays, its impression is left in the rock and can be seen if the rock is broken open.

moraine -- n. A mound or ridge of sediment deposited by a glacier; lateral moraine- n. deposited to the side of a glacier; terminal moraine- n. deposited to the front of a glacier; ground moraine- n. deposited on the land surface.

oceanic crust -- n. The Earth's crust which is formed at mid-oceanic ridges, typically 5 to 10 kilometers thick with a density of 3.0 grams per centimeter cubed.

oceanic trench -- Deep steep-sided depression in the ocean floor caused by the subduction of oceanic crust beneath either other oceanic crust or continental crust.

orogeny -- n. The tectonic processes of folding, faulting, and uplifting of the earth’s crust that result in the formation of mountains.

outcrop -- Any place where bedrock is visible on the surface of the Earth.

paleosol -- Soil horizon from the geologic past.

peat -- n. A deposit of partly decayed plant remains in a very wet environment; marsh or swamp deposit of plant remains containing more than 50 percent carbon.

permineralization -- Fossilization process that occurs when minerals, carried by ground water, enter and harden in the pores of an organism’s structures.

Phanerozoic -- n. The geologic eon that includes the interval of time from approximately 543 million years ago to the present, comprising the Paleozoic, Mesozoic, and Cenozoic eras.

pillow lava -- Lava extruded beneath water characterised by pillow-type shapes.

plate -- n. Rigid parts of the Earth's crust and part of the Earth's upper mantle that move and adjoin each other along zones of seismic activity. The theory that the crust and part of the mantle are divided into plates that interact with each other causing seismic and tecotnic activity is called plate tectonics.

pluton -- n. Any body of igneous rock that solidified below the earth’s surface.

plutonic -- Applies to igneous rocks formed beneath the surface of the Earth; typically with large crystals due to the slowness of cooling. Synonym of intrusive. Antonym of volcanic.

radio-carbon dating -- Method for determining the age of an organic substance by measuring the amount of the carbon isotope, carbon-14, remaining in the substance; useful for determining ages in the range of 500 to 70,000 years.

rebound -- v. To spring back after a weight has been removed.

red bed -- n. Sedimentary layers composed primarily of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of iron oxides; often used in reference to the Permian or Triassic sediments of the western U.S.

reef -- n. A large ridge or mound-like structure within a body of water that is built by calcareous organisms such as corals, red algae, and bivalves; barrier reef- n. A reef growing offshore from a land mass and separated by a lagoon or estuary, e.g, the Great Barrier Reef of Australia; patch reef- n. A discontinuous reef growing in small areas, separated by bare areas of sand or debris, often part of a larger reef complex.

regression -- (n) A drop in sea level that causes an area of the land to be uncovered by seawater.

replacement -- Fossilization process that occurs when an organism is completely decomposed and replaced by mineral.

rhyolite -- Highly felsic igneous volcanic rock, typically light in color; rough volcanic equivalent of granite.

rift -- n. A long, narrow crack in the entire thickness of the Earth's crust, which is bounded by normal faults on either side and forms as the crust is pulled apart; v. To split the Earth's crust; rift zone- n. The area on continents where a trough bounded by normal faults is forming; the site of crustal extension, similar to that which occurs at mid-oceanic ridges; rift basin or rift valley- n. The long, and fairly wide trough that has formed as a section of the Earth's crust has dropped down along faults, e.g., African Rift Valley in East Africa.

rock cycle -- The process through which one type of rock (igneous, sedimentary, or metamorphic) is converted into another.

salt lick -- n. A natural or artificial deposit of exposed salt that animals lick for nutrients.

sandstone -- Sedimentary rock composed of sand-sized clasts.

sea-floor spreading -- n. The process of adding to the Earth's crust at mid-ocean ridges as magma wells up and forces previously formed crust apart.

sediment -- Any solid material that has settled out of a state of suspension in liquid.

sedimentary rock -- Any rock resulting from the consolidation of sediment.

siderite -- Also called ironstone, that is a concretion of iron carbonate. Common in the Mazon Creek fossil beds.

silicification -- Process whereby silica replaces the original material of a substance. For example, silicified wood.

sill -- n. A sheet-like igneous intrusion that parallels the plane of the surrounding rock.

sinkhole -- n. A natural depression in the surface of the land caused by the collapse of the roof of a cavern or subterranean passage, generally occurring in limestone regions.

soil -- Unconsolidated materials above bedrock.

stratigraphy -- n. The study of rock layers, especially their distribution, environment of deposition, and age; stratigraphic, adj.

stratum -- A layer of sedimentary rock; plural is strata.

strike -- The direction or trend of a bedding plane or fault, as it intersects the horizontal.

subduction -- n. A geologic process in which one edge of one crustal plate is forced below the edge of another; subduct– v.; subduction zone- n. A long narrow area in which subduction is taking place, e.g. the Peru-Chile trench, where the Pacific Plate is being subducted under the South American Plate.

subsidence -- n. The sudden sinking or gradual downward settling of the Earth’s surface with little or no horizontal motion.

syncline -- A fold of rock layers that is convex downwards. Antonym of anticline.

taphonomy -- The study of what happens to a fossil, from the time of its initial creation (e.g. the death of an organism or the imprint left by the movement of an organism) and the time that the fossil is discovered by a paleontologist. For example, shells or bones can be moved my running water, and later be compressed by overlying sediment. Taphonomy is often broken into two parts, biostratinomy and the study of diagenesis.

tectonic -- adj. Describing the forces that cause the movements and deformation of Earth’s crust on a large scale, also describes the resulting structures or features from these forces.

terrane -- n. A general term used to refer to a piece of the crust that is usually smaller than a continent but larger than an island; exotic terrane- n. terrane that has an unknown origin or a different origin than its surrounding rocks.

till -- n. unstratified glacial drift consisting of clay, sand, gravel, and boulders

topography -- n. The relief features of the Earth's surface, above and below sea level; the set of landforms in a region.

trace fossil -- Evidence left by organisms, such as burrows, imprints, coprolites, or footprints. Trace fossils are not preserved parts of the organism.

transgression -- (n) A rise in sea level relative to the land.

tuff -- n. A general term for consolidated rocks made of material ejected from volcanic explosions.

turbidite -- n. The sediments or rocks that formed as a result of a turbidity flow.

turbidity current -- n. A bottom fast-flowing current that moves down a slope, depositing suspended sediments over the floor of a body of water

turbidity flow -- n. A flow of dense, muddy water moving down a slope due to a turbidity current

unconformity -- Any interruption of the continuity of a depositional sequence.

undifferentiated -- adj. Unable to distinguish between. Undifferentiated rocks: rocks for which it is not possible to specify finer age divisions.

upland -- n. (adj.) An area that is higher relative to the surrounding areas, but not mountainous; highland– syn.; lowland– ant.

uplift -- n. (v.) The process or result of raising a portion of the Earth’s crust through different tectonic mechanisms.

volcanic -- adj. Describes the action or process of magma and gases rising to the crust and being extruded onto the surface and into the atmosphere; also applies to the resulting igneous rocks that cool on the surface of the Earth, including beneath water, which typically have small crystals due to the rapidity of cooling. volcanically - adv. extrusive - syn. plutonic - ant.

volcanic arc -- n. A curved chain of islands that rise from the sea floor, usually near a continent. The convex side usually faces the open ocean, while the concave side usually faces the continent; island arc - syn.

volcanism -- n. The process by which magma and associated gases rise to the Earth’s crust and are extruded, or expelled, onto the surface and into the atmosphere.

weathering -- n. The physical, chemical, and biological processes by which rock is broken down into smaller pieces.

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