Terminology

Terminology for geology


lava


Magma poured out on surface of earth or rock solidified from such magma

magma

1- Naturally occurring silicate melt, which may contain suspended silicate crystals, dissolved gases, or both. These conditions may be met in general by a mixture containing as much as 65 percent crystals but no more than 11 percent dissolved gases.

2- Naturally occurring molten rock, generated within the Earth and capable of intrusion and extrusion, from which igneous rocks are derived through solidification and related processes. It may or may not contain suspended solids (such as crystals and rock fragments) and/or gas phases. Adj: magmatic. AGI

a channel

A narrow, sinuous channel in which a lava river moves downward and away from a central vent or fissure to feed an aa flow. At the end of eruptive activity, the lava river ordinarily drains away, leaving an open channel mostly floored with spinose aa

abyssal theory

A theory of mineral-deposit formation involving the separation and sinking of ore minerals below a silicate shell during the cooling of the Earth from a liquid stage, followed by their transport to and deposition in the crust as it was fractured (Shand, 1947). Modern thought ascribes more complex origins to mineral deposits. AGI



a axis



a. One of the three crystallographic axes used as reference in crystal description. It is oriented horizontally, front to back. b. One of the three reference axes used in describing a rock fabric possessing monoclinic symmetry, such as progressive simple shear. The a axis is the direction of tectonic transport, i.e., the direction of shear. Syn: a direction CF: b axis; c axis



a direction

See: a axis

abyssal injection

The process by which magmas, originating at considerable depths, are considered to have been driven up through deep-seated contraction fissures

active mining area

a. The area, on and beneath land, used or disturbed in activity related to the extraction, removal, or recovery of coal from its natural deposits. This term excludes coal preparation plants, areas associated with coal preparation plants, and post-mining areas. SME, 1



b. The area in which active mining takes place relative also to extraction of metal ores, industrial minerals, and other minerals of economic value



aerial mapping



The taking of aerial photographs for making maps and for geologic interpretation. AGI



Babel quartz

A variety of quartz, named for the fancied resemblance of the crystal to the successive tiers of the Tower of Babel. Syn: Babylonian quartz



banded quartz-hematite ore

Braz. In the Itabira Region of Minas Gerais, schistose, specular hematite forming alternate bands with sugary quartz. Some of the beds are auriferous and contain gold-palladium alloys with manganese oxides, native copper, and talc. Writers have given the rocks various names, such as iron-glance schist, jacutinga, quartz itabirite, and bandererz. Hess



base map

a. A map on which information may be placed for purposes of comparison or geographical correlation. Base map was at one time applied to a class of maps now known as outline maps. It may be applied to topographic maps, also termed "mother maps," that are used in the construction of many types of maps by the addition of particular data. AGI



b. A map of any kind showing essential outlines necessary for adequate geographic reference, on which additional or specialized information is plotted for a particular purpose; esp. a topographic map on which geologic information is recorded. AGI



black copper ore



An earthy, black, massive, or scaley form of copper oxide, CuO. See also: melaconite; tenorite. Hess



black gold

a. A slang American term referring to crude oil.



b. Syn: Maldonite



c. Placer gold coated with a black or dark-brown substance (such as a film of manganese oxide) so that the yellow color is not visible until the coating is removed. AGI

black mica

See: biotite

blue gold

a. A gold-iron alloy containing 25% to 33.3% iron. Camm



b. A bluish collodial solution of gold prepared by reducing a solution of gold chloride with hydrazine hydrate. Camm



blue ironstone

A bluish iron-bearing mineral; specif: crocidolite and vivianite.



chert

Granular cryptocrystalline silica, similar to flint but usually light in color. Occurs as compact

massive rock or as nodules

clastic rock

A consolidated sedimentary rock composed principally of broken fragments that are derived from preexisting rocks (of any origin) or from the solid products formed during chemical weathering of such rocks, and that have been transported mechanically to their places of deposition; e.g., a sandstone, conglomerate, or shale; or a limestone consisting of particles derived from a preexisting limestone. Syn: fragmental rock; clasolite. AGI



collapse breccia

A breccia formed by the collapse of rock overlying an opening, as by foundering of the roof of a cave or of the roof of country rock above an intrusion; e.g., a solution breccia. Syn: founder breccia



copper

a. A reddish metallic element that takes on a bright metallic luster and is malleable, ductile, and a good conductor of heat and electricity. Symbol, Cu. Occasionally occurs native, and is found in many minerals such as cuprite, malachite, azurite, chalcopyrite, and bornite. Its alloys, brass and bronze, are very important; U.S. coins are now copper alloys. Its oxides and sulfates are used as an agricultural poison and as an algicide in water purification. Handbook of Chemistry and Physics, 3



b. An isometric native metal Cu ; metallic, red, soft, ductile and malleable; sp gr, 8.9; in oxidized zones of copper deposits, formerly a major source of native copper; the only native metal to occur abundantly in large masses; commonly occurs in dendritic clusters or mossy aggregates, sheets, or in plates filling narrow cracks or fissures. See also: native copper



core drilling

a. The process of obtaining cylindrical rock samples by means of annular-shaped rock-cutting bits rotated by a borehole-drilling machine. Long



b. Drilling with a hollow bit and a core barrel to obtain a rock core.

cross section

a. A diagram or drawing that shows features transected by a given plane; specif. a vertical section drawn at right angles to the longer axis of a geologic feature, such as the trend of an orebody. AGI



b. An actual exposure or cut that shows transected geologic features.--Adj: cross-sectional. Also spelled: cross-section. AGI



c. A profile portraying an interpretation of a vertical section of the Earth explored by geophysical and/or geological methods.



d. A horizontal grid system laid out on the ground for determining contours, quantities of earthwork, etc., by means of elevations of the grid points. Seelye, 2

cross-bedded

Having minor beds or laminae inclined to the main planes of stratification, e.g., cross-bedded sandstone.

cross-sectional area

The area of a surface cut by a plane passing through the body and perpendicular to the long axis of the body if one exists. If not, any such area cut by a plane

crusher rock

a. Term used in quarrying to describe the weathered overlying rock that occurs at most quarry operations and which is sold for use as road base.



b. The total unscreened product of a stone crusher. Shell



dam



a. A barrier to keep foul air or water, from mine workings. See also: stopping; bulkhead. Fay



b. An airtight barrier to isolate underground workings that are on fire. CTD



c. The wall of refractory material, forming the front of the forehearth of a blast furnace, that is built on the inside of a supporting iron plate (dam plate). Iron is tapped through a hole in the dam, and cinder through a notch in the top of the dam. See also: Lurmann front



deformation of rocks

Any change in original shape or volume of rock masses; produced by mountain-building forces. Folding, faulting, and plastic flow are common modes of rock deformation

desert

A region with an average annual rainfall of 10 inches or less and sparse vegetation, typically having thin, dry, and crumbly soil. A desert has an aridity index greater than 4.0.

diamond

A mineral composed of elemental carbon; hardest substance known. Used as a gem and, in industry, for cutting tools.



digger



a. One that digs in the ground, as a miner or a tool for digging. Webster 3rd



b. A worker who is paid by the ton for coal produced; a miner in the stricter sense. Originally the digger mined or undermined the coal; now the term is applied to the worker who merely shoots out the coal. Fay



c. A machine for removing coal from the bed of streams, the coal having washed down from collieries of culm banks above. Zern



dolomite



Mineral composed of carbonate of calcium and magnesium, CaMg(CO3)2. Also used as rock name for formations composed largely of mineral dolomite.

earthy breccia

A breccia in which rubble, sand, and silt plus clay each constitute more than 10% of the rock. AGI

fault

Surface of rock rupture along which has been differential movement.



fold

Bend, flexure, or wrinkle in rock produced when rock was in a plastic state.



fault-fold

A structure that is associated with a combination of folding and nearly vertical faulting, in which crustal material that has been fractured into elongate strips tends to drape over the uplifted areas to resemble anticlines and to crumple into the downthrown areas to resemble synclines. AGI

fossil

Evidence of past life, such as dinosaur bones, ancient clam shell, footprint of long-extinct animal, or impression of leaf in rock

fraction

A portion of an unconsolidated sediment or of a crushed consolidated rock sample or of a crushed ore or mineral sample that has been separated by some method, and is distinguished in some manner from all the other portions (or fractions) comprising the whole sample being analyzed. Also a fraction may be separated and defined on the basis of its mineral content, its specific gravity or density, its magnetism or lack of magnetism, or its solubility or insolubility in acid.

geology

Organized body of knowledge about the earth, including physical geology and historical geology, among others.



geologic-time scale

Chronological sequence of units of earth time.

geophysics

Physics of the earth

geosyncline

Literally, "earth syncline." Term now refers, however, to a basin in which thousands of meters of sediments have accumulated, with accompanying progressive sinking of basin floor explained only in part by load of sediments. Common usage includes both accumulated sediments themselves and geometrical form of basin in which they are deposited. All folded mountain ranges were built from geosynclines, but not all geosynclines have become mountain ranges.

geochronology

The study of the relationship between the history of the Earth and time.


geothermal field

Area where wells drilled to obtain elements contained in solution in hot brines and to tap heat energy.

GIS

See: Geographic Information System



gneiss

Metamorphic rock with gneissic cleavage. Commonly formed by metamorphism of granite

gold

a. An isometric mineral, native 4[Au] ; commonly alloyed with silver or copper, possibly with bismuth, mercury, or the platinum-group metals; metallic yellow; soft and malleable; sp gr, 19.3 if pure; occurs in hydrothermal veins with quartz and various sulfides; disseminated in submarine massive effusives and in placers or nuggets, fines, and dust. b. Found in nature as the free metal and in tellurides; very widely distributed. Symbol: Au. Occurs in veins and alluvial deposits; often separated from rocks and other minerals by sluicing and panning operations. Good conductor of heat and electricity. Used in coinage, jewelry, decoration, dental work, plating, and for coating certain space satellites. It is a standard for monetary systems in many countries. Syn: palladium gold


gold amalgam

Former spelling of goldamalgam. See also: amalgam


gold quartz



Milky quartz containing small inclusions of gold; may be cut and polished for jewelry. Syn: gold matrix



gravel mine



S. Afr. A mine extracting gold from sand or gravel; also called placer mine. See also: gravel pit