Appendix:Dictionary of Mining, Mineral, and Related Terms/F/1

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A monoclinic mineral, CaB (sub 3) O (sub 5) (OH) ; colorless; fluoresces brownish-yellow under UV light; Mohs hardness, 6; associated with halite, anhydrite, and howlite in a rock-salt drill core at Rehden, Diepholz, Germany.

Fabian system

May be described as the father of freefall drilling systems, all others having originated from it, although it is not now used in its original form. See also: free fall.


a. The spatial arrangement and orientation of the components (crystals, particles, cement) of a sedimentary rock. CF: packing.

b. The complete spatial and geometrical configuration of all those components that make up a deformed rock. It covers such terms as texture, structure, and preferred orientation. Syn: rock fabric.


A company which transforms refined metal (and sometimes scrap as well) into semifabricated products, (e.g., wire, cable, tubes, strip, rods) for sale to an end-consumer. Also called semifabricator.

fabric element

A component of a rock fabric that acts as a unit in response to deformative forces.

fabric-type dust collector

A collector that utilizes a fabric or cloth to remove dust particles from the air. The basic idea is the same as that employed in vacuum cleaners, but there is usually an automatic or self-cleaning feature for recovering the dust. Fabric-type dust collectors should not be subjected to excessively abrasive or corrosive materials, or high temperatures that might injure the fabric, unless special materials have been employed for that purpose. Bags and tubes employing glass filter fabric are capable of handling gases with temperatures up to 550 degrees F (288 degrees C), and also can withstand the action of many corrosive gases. Fabric-type collectors fall into two groups on the basis of design. One uses the fabric in a closed bag or a series of small-diameter bags commonly called tubes, while the other has the fabric on a frame like a screen.


a. The surface of an unbroken coal bed at the advancing end of the working place.

b. Sedimentary beds are said to face in the direction of the stratigraphic top of the succession (or to be directed toward the younger rocks or to the side that was originally upward), so that an overturned bed facing to the east may have a dip of 45 degrees to the west. Folds are said to face in the direction of the stratigraphically younger rocks along their axial surfaces and normal to their axes; this coincides with the direction toward which the beds face at the hinge (a normal upright fold faces upward, an overturned anticline faces downward, and an asymmetric fold faces its steeper flank). Faults are said to face in the direction of the structurally lower unit. c. The principal cleavage plane of coal, at right angles to the stratification. d. The exposed surface of a coal or ore deposit in the working place where mining is proceeding. See also: coal face; face height; working face. e. An edge of rock used as a starting point in figuring drilling and blasting. f. The part of a bit in contact with the bottom of a borehole, when drilling is in progress, that cuts the material being drilled; cutting face. g. To dress a bit. h. The bottom of a drill or borehole. i. The original upper surface of a layer of rock, esp. if it has been raised to a vertical or a steeply inclined position. j. The plane surface of a mineral crystal. k. The surface exposed by excavation. The working face, front, or forehead is the face at the end of the tunnel heading, or at the end of the full-size excavation. l. A cleat or back. m. The smooth surface of the coal as contrasted to butt. n. The main cleavage; bord cleat. o. The more or less vertical surface of rock exposed by blasting or excavating, or the cutting edge of a drill hole. p. The width of a roll crusher. q. The outer surface of a pulley in contact with a belt; the outer surface of a gear, roll, or drum usually expressed in terms of inches of width. r. The end of a drive. s. In structure, the original upper surface of a stratum esp. if it has been raised to a vertical or a steeply inclined position.


The operation of directing the intake air to and along the working face of a mine. The term was used in the early part of the 18th century to describe the coursing of air naturally induced in a coal mine. See also: circulation of air.

face area

The working area in from the last open crosscut in an entry or a room, including the pillar being extracted or longwall being mined.

face belt conveyor

A light belt conveyor employed at the face. It is the type generally used in conventional machine mining.

face belt joints

Three types of face belt joints are used: (1) hinged-plate type, which is attached to the belt by means of copper rivets and interconnected by means of pins; (2) wire-hook joints, the most popular type--the hooks are inserted by means of a hand-operated machine and are connected by a flexible steel pin; and (3) spliced joint, in which a portion on each side of the belt is cut away so as to provide a splice, and this is secured by cramped-type pins, which are inserted and knocked over by hand.

face boss

In bituminous coal mining, a foreman in charge of all operations at the working faces where coal is undercut, drilled, blasted, and loaded. Also called face foreman.

face cleat

The major joint or cleavage system in a coal seam. CF: butt cleat. See also: cleat; face.

face concentration

The ratio of pithead output (tons) to length of face (yard) or tons per yard of face. The management objective is to keep this figure as high as practicable. See also: concentration of output.

face conveyor

a. Any type of conveyor employed at the working face that delivers coal into another conveyor or into a car.

b. See: underground mine conveyor. c. A conveyor, generally 10 to 100 ft (3.0 to 30.5 m) in length, used in room and pillar mining to move material from the face to a room or section conveyor. See also: armored flexible conveyor; gate conveyor.

faced crystal

Applied in the trade to a natural mass of quartz bounded by one or more of the original crystal faces.

face-discharge bit

A bit designed for drilling in soft formations and for use on a double-tube core barrel, the inner tube of which fits snugly into a recess cut into the inside wall of the bit directly above the inside reaming stones. The bit is provided with a number of holes drilled longitudinally through the wall of the bit, through which the circulation liquid flows and is ejected at the cutting face of the bit. Also called bottom-discharge bit; face-ejection bit.

face-ejection bit

See: face-discharge bit.

face entry

An entry driven at right angles to the face cleat and parallel to the butt cleat.

face equipment

Face equipment is mobile or portable mining machinery having electric motors or accessory equipment normally installed or operated inby the last open crosscut in an entry or room.

face half and half

Eng. A longwall face crossing the main cleavage planes of the seam at an angle of 45 degrees .

face hammer

Used for rough dressing stones. It has one blunt end and one cutting end.

face haulage

The transportation of mined coal from the working face to an intermediate haulage. It is accomplished by shuttle cars, conveyors, locomotives, and mine cars, or by combinations of such equipment. See: primary haulage.

face height

The vertical height of a quarry or opencast face from top to toe; i.e., the height of overburden and coal, ore, or stone. A face height is chosen that can be reached by the excavator so that all scaling of loose material can be accomplished by the machine, thus eliminating the necessity for workers to go over the face on ropes to bar off loose ground. Where the height exceeds this figure, a form of benching may be adopted. See also: face.

face left

See: face right.


See: kaliophilite. Also spelled phacellite, phacelite.

face loading pan

A shaker conveyor pan or trough that has been widened for one-half of its length to provide a greater loading surface when used at the face.

face mechanization

On a longwall face, the term implies the use of some type of cutter loader with perhaps self-advancing ports, giving a quicker turnover and higher productivity. In the case of a rock drivage the term would mean the regular use of a shovel loader. See also: conventional machine mining.

face of hole

The bottom of a borehole.


a. A location where the face of the breast or entry is parallel to the face cleats of the seam. See: face.

b. Working of a mine in a direction parallel to the natural cleats. CF: end-on.

face on end

See: end face.

face right

Position of the vertical circle of a theodolite with respect to the telescope, viewed from the eyepiece end.

face run

N. of Eng. The time during which a coal-getting machine is moving along the face.

face sampling

The cutting of pieces of ore and rock from exposed faces of ore and waste. The faces may be natural outcrops or faces exposed in surface trenches and pits. Face samples may be taken by cutting grooves or channels of uniform width and depth across the face or sections of the face or by picking off small pieces all over the face, more or less at random.

face shovel equipment

An excavator base machine fitted with boom and bucket for excavating and loading material from an exposed face above track level.

face signal

N. of Eng. A wire stretched along the face to control, directly or indirectly, the running of the face conveyor.

face signaling

The system for transmitting signals from points on a conveyor face to the operator at the control panel near the main gate. See also: signaling system.

face slip

a. The front slip of a coal seam. CF: back slip.

b. An inclined joint in coal sloping away from the hewing face.

face stone

A diamond inset in the face portion of a bit. CF: kerf stone.


a. One of the polished plane surfaces of a gemstone, cut so as to enhance the stone's brilliance and beauty.

b. To cut facets. c. A nearly planar surface produced on a rock fragment by abrasion, as by wind sandblasting, by the grinding action of a glacier, or by a stream that differentially removes material from the upstream side of a boulder, cobble, or pebble inclined at 50 degrees or less to the direction of the impinging current. d. Asymmetrically scalloped rock surfaces. Syn: flute. e. Any plane surface produced by erosion or faulting and intersecting a general slope of the land; e.g., a triangular facet. f. Any part of a landscape defined as a unit for geographic study on the basis of homogeneous topography.

faceted boulder

A boulder that has been ground flat on one or more sides by the action of natural agents, such as by glacier ice, streams, or wind. CF: faceted pebble.

faceted pebble

A pebble on which facets have been developed by natural agents, such as by wave erosion on a beach or by the grinding action of a glacier. CF: faceted boulder.

faceted spur

The end of a ridge that has been truncated or steeply beveled by stream erosion, glaciation, or faulting. See also: truncated spur.

face timbering

The placing of safety posts at the working face to support the roof of the mine. The safety post is the most important timber in a mine because exposure is greater at this point than at any other since the newly exposed top is always of unknown quality. See also: timbering.

faceting machine

A mechanical device for holding stone during grinding and polishing facets at the exact angles that theoretically produce the most brilliant stone. Rarely used in fashioning diamonds or other valuable stone where preservation of weight is more important than maximum brilliancy.

face transfer point

See: transfer point.

face wall

A wall built to sustain a face cut into the earth, in distinction to a retaining wall, which supports earth deposited behind it.


A term of wide application, referring to such aspects of rock units as rock type, mode of origin, composition, fossil content, or environment of deposition. CF: lithofacies.

facies change

A lateral or vertical variation in the lithologic or paleontologic characteristics of contemporaneous sedimentary deposits. It is caused by, or reflects, a change in the depositional environment.

facies contour

A line indicating equivalence in lithofacies development; e.g., a particular value of the sand-to-shale ratio.

facies fauna

A group of animals characteristic of a given stratigraphic facies or adapted to life in a restricted environment; e.g., the black-shale fauna of the Middle and Upper Devonian of the Appalachian region of the United States.

facies fossil

A fossil, usually a single species or a genus, that is restricted to a defined stratigraphic facies or is adapted to life in a restricted environment. It prefers certain ecologic surroundings and may exist in them from place to place with little change for long periods of time.

facies map

A map showing the distribution of different types of rock attributes or facies occurring within a designated geologic unit.


a. Aust. The main vertical joints often seen in coal seams; they may be confined to the coal, or continue into the adjoining rocks. See also: cleat.

b. A face slip or joint as opposed to a back slip. The plane is inclined towards the observer from floor to roof. c. A powdered substance (such as graphite) applied to the face of a mold or mixed with sand that forms it, to give a smooth surface to the casting. d. Applied to the original direction of a layer. e. In machining, generating a surface on a rotating workpiece by the traverse of a tool perpendicular to the axis of rotation. f. In founding, special sand placed against a pattern to improve the surface quality of the casting. g. Any material, forming a part of a wall, used as a finishing surface.

facing of strata

The direction of the top of beds is esp. important in steeply dipping or overturned beds. The tops of the beds or their facing is determined by ripple marks, graded bedding, crossbedding, mud cracks, pillow structure, etc.

fact cut

A type of cut gem bounded by planar faces as distinguished from cabochon cut or other unfaceted cut. Also called faceted cut.

factor of safety

The ratio of the ultimate breaking strength of the material to the force exerted against it. If a rope will break under a load of 6,000 lb (2,724 kg), and it is carrying a load of 2,000 lb (908 kg), its factor of safety is 6,000/2,000 = 3, or f.s 3. See also: allowable stress.

Fagersta cut

This cut is drilled with handheld equipment. The empty hole is drilled in two steps, the first as an ordinary hole and the second as an enlargement of this pilot hole. The cut is something between a four-section cut and a double-spiral cut. The Fagersta cut is drilled with light equipment, which makes it suitable for use in mines and in small drifts, where drilling with heavy machines is not profitable.


A hexagonal mineral, (Mn,Mg)Fe (sub 2) Be (sub 2) (PO (sub 4) ) (sub 4) .6H (sub 2) O ; forms tufts, rosettes, or botryoidal masses of fibers coating primary minerals, such as muscovite and quartz; in pegmatites, Minas Gerais, Brazil.


A term originally used by German miners to indicate a band of sulfide impregnation in metamorphic rocks. The sulfides are too abundant to be classed as accessory minerals, but too sparse to form an ore lens. Fahlbands have a characteristic rusty-brown appearance on weathering.


Ger. A gray copper ore. Sometimes called fahl ore. Syn: tetrahedrite; tennantite.


Altered cordierite.


Commonly used thermometer scale in which the freezing point of water is 32 degrees and the boiling point is 212 degrees . To convert from the Fahrenheit scale to the centigrade or Celsius scale, subtract 32 and multiply by 5/9. Symbol, F. See also: temperature.

Fahrenwald machines

These include (1) a hydraulic classifier and (2) a flotation cell marketed as the Denver Sub A.

failed hole

A drill hole loaded with dynamite that did not explode.

failure by rupture

See: shear failure.


A hexagonal mineral, K (sub 2) Ca(CO (sub 3) ) (sub 2) ; dimorphous with bueschliite; in fused wood ash in partly burned trees.


a. A triclinic mineral, Ca (sub 2) (Mn,Fe)(PO (sub 4) ) (sub 2) .2H (sub 2) O ; transparent pearly to subadamantine; in granite pegmatites in Fairfield County, CT, as an alteration of dickinsonite and a pseudomorph after rhodochrosite.

b. The mineral group cassidyite, collinsite, fairfieldite, messelite, and roselite-beta. Syn: leucomanganite.


a. A device that lines up cable so that it will wind smoothly onto a drum.

b. Applies to the swivel pully on the drag rope of a dragline excavator. c. A block, ring, or strip of plank with holes that serves as a guide for the running rigging or for any ship's rope and keeps it from chafing.

fairy stone

a. A cruciform-twinned crystal of staurolite, used as a curio stone without fashioning for adornment. The term is also applied as a syn. of staurolite, and esp. to the variety occurring in the form of a twinned crystal. See also: staurolite.

b. Any of various odd or fantastically shaped calcareous or ferruginous concretions formed in alluvial clays. c. A fossil sea urchin. d. A stone arrowhead.

fake reflection

Accidental lineup of disturbances on a seismogram simulating a reflection.

Falconbridge process

Recovery of nickel from a nickel-copper matte. After crushing and roasting to remove sulfur, the copper is acid-leached, filtered off, and electrolyzed. The residual solids are melted, cast as anodes, and refined to produce nickel.

falding furnace

A mechanically raked muffle furnace having three hearths with combustion flues under the lowest hearth.


a. A mass of rock, coal, or ore that has collapsed from the roof or sides of a mine roadway or face. Falls of ground are responsible for the greatest proportion of underground deaths and injuries.

b. A length of face undergoing holing or breaking down for loading. c. The rolling of coal from the face into the room, usually as the result of blasting; sometimes the amount blasted down. Locally, also the caved roof after the coal is extracted. d. To blast, wedge, or in any other way to break down coal from the face of a working place. e. A system of working a thick seam of coal by falling or breaking down the upper part after the lower portion has been mined. CF: caving system. f. A mass of roof or side that has fallen in any subterranean working or gallery, resulting from any cause whatever. g. The collapse of the roof of a level or tunnel, or of a flat working place or stall; the collapse of the hanging wall of an inclined working place or stope. h. To crumble or break up from exposure to the weather; clays, shales, etc., fall.


Movable supports for a cage. Also called fangs; keps.

fallhammer test

A test used to determine impact sensitivity of an explosive conducted by allowing standard hammer weights to fall on an amount of confined explosive charge and measuring the fall height required to decompose or detonate the charge.

falling-head test

A soil permeability test in which the borehole is filled up with water and the rate at which the water falls is observed.

falling-pin seismometer

A limit recorder of the intensity of ground vibrations initiated by a quarry or opencast blast. It consists essentially of a level glass base on which a number of pins 1/4 in (0.64 cm) in diameter and of lengths ranging from 6 to 15 in (15 to 38 cm) are stood upright. The pins stand inside hollow steel rods so that each pin can fall over independently of the others. The longer the pin, the less energy required to topple it. In practice it has been accepted that if the shorter pins (up to 10 in or 25 cm) remain standing, then there is no possibility of structural damage to a building by a quarry blast. See also: vibrograph.

falling slag

Blast furnace slag that contains sufficient calcium orthosilicate to render it liable to fall to a powder when cold. Such a slag is precluded from use as a concrete aggregate by the limits of composition specified in British Standards 1047.

fall line

An imaginary line or narrow zone connecting the waterfalls on several adjacent near-parallel rivers, marking the points where these rivers make a sudden descent from an upland to a lowland, as at the edge of a plateau; specif. the fall line marking the boundary between the ancient, resistant crystalline rocks of the Piedmont Plateau and the younger, softer sediments of the Atlantic Coastal Plain in the Eastern United States. It also marks the limit of navigability of the rivers. Syn: fall zone.

fall of ground

Rock falling from the roof into a mine opening. See also: fall.

fall ridder

See: bordroom man.

fall table

A hinged platform to cover the mouth of a shaft.

fall velocity

See: settling velocity.

fall zone

See: fall line.

false amethyst

An early name for violet-colored fluorite when cut as a gem. Other colors of the same mineral were called false emerald, ruby, sapphire, or topaz.

false anticline

An anticlinelike structure produced by compaction of sediment over a resistant mass, such as a buried hill or reef.

false bedding

See: crossbedding; current bedding.

false bottom

a. An apparent bedrock underlying an alluvial deposit that conceals a lower alluvial deposit; e.g., a bed of clay or sand cemented by hydrous iron oxides, on which a gold placer deposit accumulates, and under which there is another alluvial deposit resting on bedrock.

b. A strip of wire screening nailed to a wooden frame that fits into the bottom of a sluice box to trap fine sand containing gold. When the frame is removed, the fine sand, containing gold, is scraped up and placed in pans for washing down. False bottoms are employed for saving both fine and coarse gold. c. Aust.; U.S. A bed of drift lying on the top of other alluvial deposits, beneath which there may be a true bottom or a lower bed of wash resting directly upon the bedrock. d. A floor of iron placed in a puddling machine. e. A flat, hexagonal or cylindrical piece of iron upon which the ore is crushed in a stamp mill; the die. In Victoria, Australia, it is called stamper bed. f. An insert put in either member of a die set to increase the strength and improve the life of the die.

false chrysolite

See: moldavite.

false cleavage

a. See: strain-slip cleavage.

b. A secondary cleavage superposed on slaty cleavage. c. Closely spaced surfaces, a millimeter or so apart, along which a rock splits. The surfaces are either minute faults or the short limbs of small folds. d. A quarrying term for minor cleavage in a rock, such as slip cleavage, to distinguish it from the dominant cleavage. Geologically, the term is misleading and should be avoided.

false diamond

Any colorless mineral that if cut and polished makes a brilliant gem; e.g., zircon, corundum, and topaz. Having less dispersion, lower refractive index, and birefringence, they are easily distinguished from diamond.

false equilibrium

The growth of a metastable or monotropic phase under conditions apparently indicating true equilibrium, as in the development of andalusite crystals in which sillimanite actually represents the stable phase.

false form

See: pseudomorph.

false galena

An obsolete term for blende. See also: sphalerite.

false gate

A gate carried forward in the seam thickness only (which must be over 3 ft or 0.9 m), with cut-throughs as required to the main gate. The false gate has a short conveyor that takes the face conveyor coal and delivers it to the main gate conveyor through a crosscut a short distance behind the face. This layout enables the main gate rippings to be worked on three shifts.

false gossan

A laterally or vertically displaced, rather than indigenous, iron-oxide zone. It may be confused with the iron oxide of a gossan, which is weathered from underlying sulfide deposits.

false horizon

See: artificial horizon.

false hyacinth

See: essonite.

false lapis

a. See: lazulite.

b. Agate, jasper, or other varieties of chalcedony dyed blue. Syn: false lapis lazuli; Swiss lapis; German lapis.

false lapis lazuli

See: false lapis.

false-leg arches

Temporary arch legs used adjacent to the face conveyor in an advance gate to allow the conveyor to be moved forward and still maintain the gate supports. The conveyor side half-arch is temporarily replaced by props and crossbars (false legs). When the conveyor has passed, the half-arch is bolted back in position.

false ruby

Some garnets, e.g., Arizona ruby, Bohemian ruby, Cape ruby, and some spinels, e.g., balas ruby, ruby spinel, are ruby colored. See also: balas ruby; Elie ruby.

false stratification

An old term for cross-stratification.

false stull

A stull so placed as to offer support or reinforcement for a stull, prop, or other timber.

false topaz

a. A transparent yellow variety of quartz, specif. citrine. See also: citrine. CF: gold topaz; topaz; Madeira topaz.

b. A yellow variety of fluorite.


A tetragonal mineral, Cu (sub 3) SbS (sub 4) ; stannite group; occurs with enargite, tetrahedrite-tennantite, chalcopyrite, and covellite in copper ores worldwide, notably at Mankayan, Luzon, Philippines; Famatina, Argentina; and Butte, MT.


The basic unit of the clan of igneous rocks.


a. To drill a number of boreholes each in a different horizontal or vertical direction from a single drill setup.

b. An accumulation of debris brought down by a stream descending through a steep ravine and debouching in the plain beneath, where the detrital material spreads out in the shape of a fan, forming a section of a very low cone. See also: alluvial fan.

fan cleavage

Cleavage that, if studied over a large enough area, dips at different angles so that, like the ribs of a fan, it converges either upward or downward.

fan cut

A cut in which holes of equal or increasing length are drilled in a pattern on a horizonal plane or in a selected stratum to break out a considerable part of it before the rest of the round is fired; the holes are fired in succession in accordance with the increasing angle they form in relation to the face.


A term applied to semiprecious stones prized for qualities other than intrinsic value.

fancy lump coal

a. Soft coal from which all slack and nut coal has been removed.

b. Ark. Semianthracite coal of larger size than grate coal.

fan drift

a. The short tunnel connecting the upcast shaft with the exhaust fan. See also: ventilation.

b. The enclosed airtight passage, road, or gallery from the mine to the fan. c. The passage or duct for the intake of a ventilating fan on a mine. d. An airway leading from a mine shaft, or airway, to a fan.

fan drift doors

When there are two fans at a mine it is necessary to install isolation doors for each drift leading to a fan in order to prevent the working fan from drawing air from the outside atmosphere. With modern fan layouts, the fan drift may be 5 m or more square and pass 300 m (super 3) /s of air and sometimes more. Modern fan drift doors can be fixed in any position from fully open to fully closed and can be manipulated by one person from outside the fan drift. Doors of the butterfly type are often used and can be opened manually or by power. See also: main separation door.

fan efficiency

The ratio obtained by dividing useful power output by power input. This is expressed as a percentage. Fan efficiency is understood to mean that air power is calculated from volume flowing and total pressure, on the assumption that the air does not change in volume. The velocity head, present in the air leaving the evase, is considered as a loss. The power input is that supplied to the fan shaft and thus includes the loss in the fan bearings but excludes all losses in the drive.

fan exhaust

An electric fan used for the removal of enamel dust from the spray booth, or fumes from the pickle room, thus safeguarding the health of the worker.

fan fireman

In bituminous coal mining, a person who tends and fires the boiler generating steam for driving fans used for mine ventilation.

fan fold

A fold with a broad hinge region and limbs that converge away from the hinge.

fang bolt

Used for attaching ironwork to timber. The nut is a plate with teeth, which bite into the wood. To tighten, the bolt is turned while the nut remains stationary.


A sedimentary rock consisting of slightly waterworn, heterogeneous fragments of all sizes, deposited in an alluvial fan and later cemented into a firm rock; it is characterized by persistence parallel to the depositional strike and by rapid thinning downdip.

fan laws

The general fan laws are the same for either axial-flow or centrifugal fans. These laws are as follows: (1) air quantity varies directly as fan speed; quantity is independent of air density (twice the volume requires twice the speed); (2) pressures induced vary directly as fan speed squared, and directly as density (twice the volume develops four times the pressure); (3) the fan-power input varies directly as the fan speed cubed and directly as the air density (twice the volume requires eight times the power); and (4) the mechanical efficiency of the fan is independent of the fan speed and density.


Scot. A small portable hand fan.

Fanning's equation

Frictional pressure drop (Delta p (sub t) ) of fluid flowing in a pipe; Delta p (sub t) = 2f(v (super 2) /g)(l/d) , where f is a function of the Reynolds number, v = rate of flow, g is acceleration due to gravity, l and d are length and diameter of pipe.

Fann viscosimeter

A specific make of viscosimeter. See also: viscometer.

fan rating

The head, quantity, power, and efficiency to be expected when a fan is operating at peak efficiency.

fan scarp

A fault scarplet or small fault scarp entirely in piedmont alluvium or in an alluvial fan.

fan shaft

a. The ventilating shaft to which a mine fan is connected.

b. The spindle on which a fan impeller is mounted.

fan shooting

A type of seismic survey in which detectors are laid out along an arc so that each detector is in a different direction at roughly the same distance from a single shot point. It was used in the 1920's and 1930's to detect the presence of shallow salt domes intruding low-velocity sediments. Syn: arc shooting.

fan static head

See: fan static pressure.

fan static pressure

a. The total ventilating pressure required to circulate the air through a mine less the natural ventilation pressure. Also called fan useful pressure.

b. The difference between fan total pressure and fan velocity pressure. Syn: fan static head.

fan structure

The fold structure of an anticlinorium.

fan total head

Equal to the fan static head plus the velocity head at the fan discharge corresponding to a given quantity of air flow. See also: total ventilating pressure.

fan total pressure

The algebraic difference between the mean total pressure at the fan outlet and the mean total pressure at the fan inlet.

fan velocity pressure

The velocity pressure corresponding to the average velocity at the fan outlet.

Far East Rand

S. Afr. The area between Boksburg and Heidelburg, Transvaal, limited in the north and east by the outcrops or sub-outcrops of the Main Reef, but not yet limited in the south.

farewell rock

The highest rock formation of the Millstone Grit of South Wales, occurring immediately beneath the Coal Measures. Since all workable coal seams occur in the Coal Measures, it is useless to search for coal in these rocks, hence the miner's term.

Farrar process

Method of case-hardening iron by use of ammonium chloride, manganese dioxide, and potassium ferrocyanide.


A monoclinic mineral, Mg (sub 3) (PO (sub 4) ) (sub 2) , with iron and silicon present; colorless, wax-white, or yellow; peripheral to olivine nodules in the Springwater pallasite meteorite discovered near Springwater, SK, Canada.

fascicular schist

A schist with elongated ferromagnesian minerals lying in a plane but otherwise unoriented.

fashioned gemstone

Gemstone that has been cut and polished.

Fashoda garnet

Dark-red to brownish-red pyrope garnet from Tanzania, the clear blood-red specimens used as gems.


a. See: augite.

b. Ferrian aluminian diopside or augite.

fast cord

Igniter cord consisting of three central paper strings coated with a black powder composition and held together with cotton countering. These are then enclosed in an extruded layer of plastic incendiary composition and finished with an outer plastic covering. The overall diameter of fast igniter cord is approximateiy 0.10 in (2.5 mm).

fast country

Solid or undisturbed rock. Syn: fast ground.

fast-delay detonation

A loosely applied term for any method for the firing of blasts involving the use of the blasting timer or millisecond-delay caps.

fast end

a. The part of the coalbed next to the rock.

b. A gangway with rock on both sides. See also: loose end. c. The limit of a stall in one direction, or where the face line of the adjoining stall is not up to or level with, nor in advance of, it.

fast feed

See: fast gear.

fast-feed gear

See: fast gear.

fast gear

a. As used by drillers in referring to the feed gears in a gear-feed swivel head, the pair of gears installed in the head that produces the greatest amount of bit advance per revolution of the drill stem. Also called fast feed; high feed.

b. As used by drillers in referring to the speed at which the drill motor rotates the drill stem or hoist drum, the transmission gear position giving the fastest rotation per engine revolutions per minute.

fast ground

See: fast country.

fast junking

See: junking.

fast line

That portion of the cable or wire line, reeved through a block and tackle, that runs from the stationary block to the hoisting drum on a drill machine. CF: deadline.

fast powder

Dynamite or other explosive having a high-speed detonation.

fast side

a. The rock adjoining the coal.

b. The end of the face where there is a solid face more or less at right angles.

fat clay

A cohesive and compressible clay of high plasticity, containing a high proportion of minerals that make it greasy to the feel. It is difficult to work when damp, but strong when dry. CF: lean clay. Syn: long clay.


A continuous profile of the depth obtained by echo soundings.


An instrument used in measuring the depth of water by the time required for a sound wave to travel from surface to bottom and for its echo to be returned. It may also be used for measuring the rise and fall of the tides in offshore localities.


The weakening or failure of a material after many repetitions of a stress that of itself is not strong enough to cause failure.

fatigue limit

The maximum stress below which a material can presumably endure an infinite number of stress cycles.

fatigue of metals

A deterioration in the crystalline structure and strength of metals due to repeated stresses above a certain critical value. See also: annealing.

fatigue ratio

The ratio of the fatigue limit for cycles of reversed flexural stress to the tensile strength.

fat stone

Stone with fracture surfaces having a greasy luster. Syn: nepheline.

fatty amber

A yellowish amber resembling goose fat; not as opaque as cloudy amber. Syn: flohmig amber.

fatty luster

Having the brilliancy of a freshly oiled reflecting surface; characteristic of slightly transparent minerals, e.g., serpentine and sulfur. Syn: greasy luster.

Fauck's boring method

An earlier percussive boring method used largely in Europe for exploration, etc. The cutting tool is given a rapid but very short stroke, and the hole is flushed by water passing down through the hollow rods. No beam is used, but the rope to which the boring tools are suspended has an up-and-down motion imparted to it by an eccentric. The arrangement gives up to 250 strokes/min with a stroke length as low as 3-1/4 in (8.3 cm).


The tymp arch or working arch of a furnace.

faulding boards

Catches in a mine shaft to facilitate the stopping of the cage at intermediate coal seams.


a. A fracture or a fracture zone in crustal rocks along which there has been displacement of the two sides relative to one another parallel to the fracture. The displacement may be a few inches or many miles long.

b. A break in the continuity of a body of rock. It is accompanied by a movement on one side of the break or the other so that what were once parts of one continuous rock stratum or vein are now separated. The amount of displacement of the parts may range from a few inches to thousands of feet. Various descriptive names have been given to different kinds of faults, including closed fault; dip fault; dip-slip fault; distributive fault; flaw fault; gravity fault; heave fault; hinge fault; horizontal fault; longitudinal fault; normal fault; oblique fault; oblique slip fault; open fault; overthrust fault; parallel displacement fault; pivotal fault; reverse fault; rotary fault; step fault; strike fault; strike-slip fault; thrust fault; transcurrent fault; translatory fault; underthrust; vertical fault; want. c. In coal mining, a sudden thinning or disappearance of a coal seam. Also known as a want or pinchout.

fault basin

A region depressed relative to the surrounding region and separated from it by bordering faults.

fault bench

A small fault terrace.

fault block

a. A mass bounded on at least two opposite sides by faults. It may be elevated or depressed relative to the adjoining region, or it may be elevated relative to the region on one side and depressed relative to that on the other side.

b. A body of rock bounded by one or more faults. c. The displaced mass of rocks on either side of a fault plane. See also: footwall; hanging wall.

fault-block mountain

See: block mountain.

fault breccia

a. The assemblage of angular fragments resulting from the crushing, shattering, or shearing of rocks during movement on a fault; a friction breccia. It is distinguished by its cross-cutting relations, by the presence of fault gouge, and by blocks with slickensides.

b. Angular to subangular fragments of crushed rock, up to several meters in size, filling a fault. Syn: fault stuff. CF: tectonic breccia.

fault casing

A layer of hardened clay lining the fault plane and often showing groovings and striae due to the rock movement along the fault plane. See also: fault gouge.

fault complex

An intricate system of interconnecting and intersecting faults of the same or different ages.

faulted mountain

See: block mountain.

fault embayment

A depressed region in a fault zone or between two faults, invaded by the sea. The Red Sea and Tomales Bay on the San Andreas fault in California are examples.

fault escarpment

See: fault scarp.

fault fissure

A fissure that is the result of faulting. It may or may not be filled with vein material.


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.

fault gap

A depression between the offset ends of a ridge developed on a resistant rock layer that has been displaced by a transverse fault.

fault gouge

A layer of hardened clay lining a fault plane, commonly showing grooves and striae indicating the direction of most recent movement. Syn: fault casing. CF: slickensides. See also: clay gouge; gouge.

fault groove

One of the undulations on a fault surface, deeper than fault striae but similarly formed. They record larger movements and have greater significance as indicating the direction of movement.

fault growth

Intermittent, small-scale movement along a fault surface that, accumulated, results in considerable displacement.

fault heave

The amount of lateral movement of the strata at a fault. The fault throw and heave are essential elements of a fault and form basic values when exploring and driving to recover the disrupted coal seam. See also: fault shift.


The process of fracturing and displacement that produces a fault.

fault inlier

An isolated exposure of the overridden rock in a region of thrust faulting. It is surrounded by rocks of the overriding block and is thus separated from other surface exposures of rock like itself.

fault line

The intersection of a fault surface or a fault plane with the surface of the Earth or with any artificial surface of reference. Syn: fault trace; fault trend.

fault-line scarp

An escarpment that is the result of differential erosion along a fault line rather than the direct result of movement along the fault; e.g., the east face of the Sierra Nevada in California.

fault-line valley

A valley that follows the line of a fault. Fault valleys are usually straight for long distances.

fault mosaic

An area divided by intersecting faults into blocks that have settled in varying degrees.

fault plane

A fault surface without notable curvature. See also: plane. CF: fault surface.

fault scarp

An escarpment that owes its relief to a line of faulting, the escarpment occurring on the upthrown side of the fault. See also: scarp.

fault set

A group of faults that are parallel, or nearly so, and that are related to a particular deformational episode. CF: fault system.

fault shift

The lateral movement of the rocks at a fault. In a normal fault it represents the barren ground on a plan of the area (coal mining). Syn: fault heave. See also: shift.

fault striae

The scratches on faulted surfaces caused by forced movement of particles or projecting hard points against the fault walls. They may indicate the direction of movement on the fault. CF: slickensides.

fault strike

The direction, with respect to north, of the intersection of the fault surface, or of the shear zone, with a horizontal plane. See: strike.

fault stuff

Rock filling a fault. See also: fault breccia.

fault surface

The surface of a fracture along which dislocation has taken place. CF: fault plane.

fault system

Two or more fault sets that were formed at the same time. CF: fault set.

fault terrace

An irregular, terracelike tract between two fault scarps, produced on a hillside by step faulting in which the downthrow is systematically on the same side of two approx. parallel faults. CF: fault bench.

fault trace

See: fault line; rift.

fault trap

A trap, the closure of which results from the presence of one or more faults.

fault trend

See: fault line.

fault trough

See: rift valley.

fault-trough coast

See: fault embayment.

fault vein

A mineral vein deposited in a fault fissure.

fault wedge

A wedge-shaped block of rock between two faults.

faulty structure

Irregularities of gemstone crystallization and subsequent breakage or separation, such as cleavage cracks, clouds, or feathers.

fault zone

A fault that is expressed as a zone of numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as hundreds of meters. CF: step fault. Syn: distributive fault. Less preferred syn., shatter belt.


The entire animal population, living or fossil, of a given area, environment, formation, or time span. CF: flora. Adj. faunal.


Of or pertaining to a natural assemblage of animals.


A triclinic mineral, (Zn,Cu)Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 8) .4H (sub 2) O ; turquoise group; in fine grained apple-green masses in Eureka County, NV.

Faust jig

A plunger-type jig, usually built with multiple compartments. It has three distinguishing features: (1) plungers on both sides of the screen plate, are accurately synchronized; (2) the refuse is withdrawn through kettle valves near the overflow lips in the respective compartments; and (3) the hutch is commonly discharged periodically by the operator by means of suitable hand valves operated from the working floor. This jig is used extensively on slack sizes of bituminous coal.


A system of drilling that provides for the continuous removal of the detritus from the well by means of a water flush or current of water.


Braz. In the diamond fields, brown pebbles consisting of a hydrated phosphate, or of titanium and zirconium oxides; regarded as good indications of the presence of diamonds.

favorable locality

The experienced prospector always seeks a favorable locality, which may be in the neighborhood of a mining district or else in a locality that contains favorable rocks and structures and appears as if it might contain the mineral sought. See also: critical area.


An orthorhombic mineral, 4[Fe (sub 2) SiO (sub 4) ] ; olivine group, with iron replaced by magnesum toward forsterite or by manganese toward tephroite; greenish-yellow to yellowish-amber; a common rock-forming mineral in iron-rich metasediments, quartz syenites and granites, ferrogabbro, and some felsic and alkaline volcanic rocks.

Fayol's theory

See: harmless depth theory.


Shrop. Workable measures, usually ironstone. Syn: fey.

feasibility studies

Studies gathering together the information that is required for a decision whether and how to proceed further. A study of this kind may vary from a preliminary estimate of mill cost to a very complete survey that may include a market analysis, mining plan with ore grades and mining cost, metallurgical testing, process development, plans for the mill, cash flow analysis, etc.

feather alum

See: alunogen; halotrichite.

feather amphibolite

A metamorphic rock in which porphyroblastic crystals of amphibole (usually hornblende) tend to form stellate or sheaflike groups on the planes of foliation or schistosity. CF: amphibolite. Syn: garbenschiefer.

feather edge

a. The thin end of a wedge-shaped piece of rock or coal.

b. A sharp edge, such as that produced when a brick is cut lengthwise from corner to corner to produce a triangular cross section. See also: knife edge.

feather ends

Firebricks with tapered ends.

feather gypsum

See: satin spar.

feather metal

Copper granulated by being poured molten into cold water.

feather ore

a. See: jamesonite.

b. A capillary, fibrous, or feathery habit of an antimony-sulfide mineral, specif. jamesonite, but including stibnite and boulangerite.

feather quartz

Imperfect quartz crystals that meet at an angle of a crystallographic plane so that a cross section somewhat resembles a feather.

feathers of litharge

Litharge crystals.

fecal pellet

An organic excrement, mainly of invertebrates, occurring esp. in modern marine deposits but also fossilized in some sedimentary rocks; usually of a simple ovoid form less than a millimeter in length, or more rarely rod-shaped with longitudinal or transverse sculpturing, devoid of internal structure, and smaller than a coprolite. Also spelled faecal pellet.

Federov stage

See: universal stage.


a. Material treated for removal of its valuable mineral contents. Also, feed to any machine or process along a mill's flow line. Also called mill-head ore.

b. The process of supplying material to a conveying or processing unit. c. The forward motion imparted to the drills or cutters of a rock-drilling or coal-cutting machine. d. A mechanism that pushes a drill into its work. e. The longitudinal movements imparted to a drill stem to cause the bit to cut and penetrate the formation being drilled. f. See: drill feed. g. The distance that the drill stem on a diamond drill may be advanced before the rods must be rechucked. h. In stonecutting, sand and water employed to assist the saw blade in cutting.

feed control

System of valves or other mechanical device controlling the rate at which longitudinal movements are imparted to the diamond- or rock-drill stem and/or the cutting teeth on a coal-cutting machine.

feed-control valve

A small valve, usually a needle valve, on the outlet of the hydraulic-feed cylinder on the swivel head of a diamond drill; used to control minutely the speed of the hydraulic piston travel and, hence, the rate at which the bit penetrates the rock being drilled. Also called drip valve; needle valve.

feed-end blocks

In rotary kilns, special fire-clay shapes or rotary-kiln blocks so installed as to reduce the kiln diameter.


a. Small fissures or cracks through which methane or other gases escape from the coal. As working faces are advanced, fresh feeders are encountered in each fall of coal.

b. Any flow of water or gas entering a mine. c. A conveyor or bunker structure for delivering coal or other broken material at a controllable rate. See also: feeder conveyor; Lofco car feeder. d. A flow of water from the strata or from old workings. e. A small ore vein leading to a larger one. See also: feeder vein.

feeder and catchers tables

A pair of reversible conveyors, entry and exit, which provide for repeat feeding of metal being processed through a rolling mill.

feeder breaker

A portable feeding and crushing unit which can move on its own or often be installed in a stationary position. The unit has a feed chain (often referred to as a flight chain) inside a shallow built-on hopper that drags the mined ore into a rotating breaker head (shaft), which has various sizes of breaker heads (known as piks). These piks rotate downward as the chain drags the stone or ore into it, crushing the ore to various sizes depending on the height of the mounted rotating breaker head. Syn: stamler.

feeder circuit

A feeder circuit is a conductor or group of conductors and associated protective and switching devices installed on the surface, in mine entries, or in gangways, but not extending beyond the limits set for permanent mine wiring.

feeder connection

The opening or surrounding blocks in a furnace wall to receive the channel leading to the feeder.

feeder conveyor

a. A short auxiliary conveyor designed to receive coal from the face conveyor and load it onto the gate conveyor. Also called stage loader. See also: feeder; gate-end feeder; gate-end loader.

b. Any conveyor that transports material to another conveyor.

feeder trough

In a duckbill, the trough that is attached to the conveyor pan line and serves as a base on which the feeder trough rides.

feeder vein

A small ore-bearing vein joining a larger one. See also: feeder.

feed gear

The gearing or assemblage of three to four pairs of matched gears in a gear-feed swivel head of a diamond drill by means of which the drill string coupled to the feed screw is made to advance and penetrate the formation. See also: gear.


See: swivel head.

feeding baffle

A door or gate that can be opened or closed to regulate the discharge of material from a hopper, bin, or chute.

feed pressure

a. Total weight or pressure, expressed in pounds or tons, applied to drilling stem to make the drill bit cut and penetrate the formation being drilled.

b. Pressure, expressed in pounds per square inch, required to force grout into a rock formation. CF: injection pressure.

feed pump

The pump that provides a steam boiler with feedwater.

feed rate

Rate at which a drilling bit is advanced into or penetrates the rock formation being drilled, expressed in inches per minute, inch per bit revolution, number of bit revolutions per inch of advance, or feet per hour. Also called cutting rate; forward speed. Syn: penetration rate; bit feed; cutting speed; drill rate; penetration feed.

feed ratio

The number of revolutions a drill stem and bit must turn to advance the drill bit 1 in (2.54 cm) when the stem is attached to and rotated by a screw- or gear-feed-type drill swivel head with a particular pair of the set of gears engaged. (E.g., when a screw-feed swivel head of a diamond drill equipped with three pairs of gears, having a feed ratio of 100, 200, and 400, is operated with the 100-pair engaged, the drill stem must revolve 100 times to advance the bit 1 in, if the 200-pair is engaged, the drill stem rotates 200 times/in (508 times/cm) advanced, and if the 400-pair is engaged the stem must rotate 400 times to advance the bit 1 in).

feed shaft

A short shaft or countershaft in a diamond-drill gear-feed swivel head rotated by the drill motor through gears or a fractional drive and by means of which the engaged pair of feed gears is driven. Syn: feed spindle.

feed speed

Normally used by drillers to denote feed ratios.

feed spindle

See: feed shaft. Sometimes incorrectly used as a synonym for drive rod and/or feed screw.

feed travel

The distance a drilling machine moves the steel shank in traveling from top to bottom of its feeding range.


Water that is often purified, heated to nearly boiler temperature, and deaerated before being pumped into a steam boiler by the feed pump.

fee engineer

Person (usually an engineer) who looks after the interest of the owner of mineral rights. Specific duties are to check on the amount of ore mined by the lessor (operator), see that no undue waste is permitted, and see that royalties are paid according to contract.


Refuse or dirt from ore or coal.


A jewel diamond having its grain in regular layers. CF: naetig.


a. A monoclinic or triclinic mineral with the general formula XZ (sub 4) O (sub 8) where (X= Ba,Ca,K,Na,NH (sub 4) ) and (Z= Al,B,Si); a group containing two high-temperature series, plagioclase and alkali feldspar; colorless or white and clear to translucent where pure; commonly twinned; 90 degrees or near 90 degrees prismatic cleavage; Mohs hardness, 6. Constituting 60% of the Earth's crust, feldspar occurs in all rock types and decomposes to form much of the clay in soil, including kaolinite. Also spelled felspar, feldspath. CF: sanidine. See also: moonstone.

b. The mineral group albite, andesine, anorthite, anorthoclase, banalsite, buddingtonite, bytownite, celsian, hyalophane, labradorite, microcline, oligoclase, orthoclase, paracelsian, plagioclase, reedmergnerite, sanidine, and slawsonite.

feldspar convention

See: rational analysis.

feldspar jig

A small coal washer to deal with the 1/2- to 0-in (1.3- to 0-cm) range. It works on the same basic principle as the Baum washer, but in view of the small-size material a feldspar (sp gr, 2.6) bed is provided on the perforated grid plates to prevent the bulk of the feed from passing straight through the perforations. Stratification of the raw feed takes place in the usual way.

feldspar sunstone

See: sunstone.

feldspar-type washbox

A washbox to clean small coal, in which the pulsating water is made to pass through a layer of graded material, such as feldspar, situated on top of the screen plate. See: jig.


Said of a rock or other mineral aggregate containing feldspar.

feldspathic emery

Emery similar to spinel emery but contains in addition from 30% to 50% plagioclase feldspar. Pure magnetite often is found in streaks within this mass.

feldspathic graywacke

A graywacke characterized by abundant unstable materials; specif., a sandstone containing generally less than 75% of quartz and chert and 15% to 75% detrital clay matrix, and having feldspar grains (chiefly sodic plagioclase, indicating a plutonic provenance) in greater abundance than rock fragments (indicating a supracrustal provenance) (Pettijohn, 1954; 1957). CF: lithic graywacke.

feldspathic sandstone

A feldspar-rich sandstone; specif., a sandstone intermediate in composition between an arkosic sandstone and a quartz sandstone, containing 10% to 25% feldspar and less than 20% matrix material of clay, sericite, and chlorite. See also: arkose.


See: feldspathoid.


The introduction of feldspar into a rock, or the replacement of other rock-forming minerals by feldspar. Material for the feldspar may come from the country rock or be introduced by magmatic or other solutions.


a. A group of comparatively rare rock-forming minerals consisting of aluminosilicates of sodium, potassium, or calcium and having too little silica to form feldspar. Feldspathoids are chemically related to the feldspars, but differ from them in crystal form and physical properties; they take the places of feldspars in igneous rocks that are undersaturated with respect to silica or that contain more alkalies and aluminum than can be accommodated in the feldspars. Feldspathoids may be found in the same rock with feldspars but never with quartz or in the presence of free magmatic silica. See also: foid; lenad.

b. A mineral of the feldspathoid group, including leucite, nepheline, sodalite, nosean, hauyne, lazurite, cancrinite, and melilite. Syn: feldspathide.


A rock having a fine granular structure, and composed chiefly of feldspar and quartz.


A constituent of portland cement clinker. Also spelled felith. See: belite; larnite.


a. One of the many names for lead ore.

b. The finer pieces of ore that pass through the riddle in sorting.


A group of minerals comprising the feldspars and feldspathoids. CF: feldspathoid.


See: block field.


A mnemonic adj. derived from (fe) for feldspar, (l) for lenad or feldspathoid, and (s) for silica, and applied to light-colored rocks containing an abundance of one or all of these constituents. Also applied to the minerals themselves, the chief felsic minerals being quartz, feldspar, feldspathoid, and muscovite. Syn: acidic; silicic. CF: mafic.


A general term for any light-colored, fine-grained or aphanitic extrusive or hypabyssal rock, with or without phenocrysts, and composed chiefly of quartz and feldspar; a rock characterized by felsitic texture. Syn: felstone; aphanite. CF: felsophyre.


A textural term ordinarily applied to dense, light-colored igneous rocks composed of crystals that are too small to be readily distinguished with the unaided eye; microcrystalline. It may also be used as a microscopic term for the groundmass of porphyritic rocks that are too fine-grained for the mineral constituents to be determined with the microscope; cryptocrystalline.


An informal term applied to any light-colored igneous rock in which the mineral grains are too small to be distinguished by the unaided eye. CF: felsite. Syn: aphanite.


An orthorhombic(?) mineral, Al (sub 4) (SO (sub 4) )(OH) (sub 11) .5H (sub 2) O ; massive; soft; snow white; associated with marcasite, stibnite, and barite at Felsoebanya, Romania. Also spelled felsoebanyite. CF: basaluminite.


A general term for any porphyritic felsite. Syn: aphanophyre. CF: vitrophyre; granophyre.


A British spelling of feldspar following an error by Kirwan.


An obsolete synonym of felsite.


See: felty.


Said of the texture of dense, holocrystalline igneous rocks consisting of tightly appressed microlites, generally of feldspar, interwoven in irregular, unoriented fashion. CF: trachytic. Syn: pilotaxitic; felted.


Said of an igneous rock having one or more normative, dark-colored iron-, magnesium-, or calcium-rich minerals as the major components of the norm; also, said of such minerals. Etymol. a mnemonic term derived from ferric + magnesium + ic. CF: basic; salic; mafic; felsic.


Fragile, weak, or slender as in the case of a thin, soft roof bed over a coal seam.

fence diagram

Three or more geologic sections showing the relationship of wells to subsurface formations. The scales diminish with distance from the foreground to give proper perspective. When several sections are used together, they form a fencelike enclosure, hence the name. Similar in some respect to a block diagram, but it has the advantage of transparency, which is not possible in a block diagram.


A thin pillar of coal, adjacent to the gob, left for protection while driving a lift through the main pillar.


A quartzo-feldspathic rock that has been altered by alkali metasomatism at the contact of a carbonatite intrusive complex. The process is called fenitization. Fenite is mostly alkalic feldspar, with some aegirine, subordinate alkali-hornblende, and accessory sphene and apatite.


See: window. Etymol. German, window.


A monoclinic mineral, FeWO (sub 4) ; wolframite series with manganese replacing iron toward huebernite; weakly ferrimagnetic; sp gr, 7.5; in quartz veins; an ore of tungsten. Syn: eisinwolframite.


A very rare, strongly radioactive, possibly orthorhombic, sulfur-yellow translucent mineral, U (sub 3) (VO (sub 4) ) (sub 2) .6H (sub 2) O ; found associated with other uranium minerals. Ferganite may be a leached or weathered product of tyuyamunite. A source of vanadium.


See: ferganite.


Monoclinic (beta) and orthorhombic minerals (Ce,Nd,La,Y)NbO (sub 4) , further speciated according to the predominant rare-earth element; dull to vitreous brownish black; in pegmatites associated with euxenite, monazite, gadolinite, and other rare-earth minerals in North Carolina, South Carolina, Virginia, Texas, Norway, Sweden, and Africa.


The process of decomposition of carbohydrates with the evolution of carbon dioxide or the formation of acid, or both.


A hexagonal mineral, (Ca,Sr) (sub 5) (AsO (sub 4) ,PO (sub 4) ) (sub 3) (OH) ; apatite group; in veinlets in manganese ore at Sitipar, Chindwara district, India.


a. A vanadium ore.

b. A monoclinic mineral, Ca (sub 3) V (sub 40) O (sub 100) .50H (sub 2) O; dull-green, cryptocrystalline to fibrous masses in the oxidized zone of the abandoned Minasragra vanadium deposit near Cerro de Pasco, Peru.

Ferraris screen

A screening machine, utilizing inclined supports, developed in southern Europe for screening small sizes of ore and sand. The wooden screen frame is set horizontally and supported on flexible wooden staves inclined at about 65 degrees from the horizontal. The connecting rod also is inclined to the screen frame, so as to be approx. at right angles to the supports.

Ferraris truss

Supporting batten used originally as a slanting support under a shaking screen. When the screen was pushed forward the radial motion of the truss caused it to rise slightly, giving a throwing motion to the load and aiding the gravity-assisted return as the reciprocating action of the screen vibrator was reversed. The principle is used in shaking tables such as the James.


Any of various classes of compounds containing iron and oxygen in the anion.

Ferrel's law

The statement that the centrifugal force produced by the rotation of the Earth (Coriolis force) causes a rotational deflection of currents of water and air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

ferreto zone

Reddish-brown or reddish zone in permeable near-surface material that is produced under conditions of free subsurface drainage by the deposition of secondary iron oxide.


Of, pertaining to, or containing iron in the trivalent state; e.g., ferric chloride, FeCl (sub 3' .

ferric furnace

A high, iron blast furnace, in the upper part of which crude bituminous coal is converted into coke.


A triclinic mineral, Fe (sub 5) (SO (sub 4) ) (sub 6) (OH) (sub 2) .20H (sub 2) O ; copiapite group.


a. A conglomerate consisting of surficial sand and gravel cemented into a hard mass by iron oxide derived from the oxidation of percolating solutions of iron salts.

b. A ferruginous duricrust. Etymol. "ferr"uginous + con"crete." CF: calcrete; silcrete.


a. A general term for an indurated soil horizon cemented with iron oxide, mainly hematite.

b. The hard crust of an iron concretion.


A member of a group of elements that are similar chemically to iron. The group includes chromium, cobalt, manganese, nickel, titanium, vanadium, and other elements.


Monoclinic and orthorhombic minerals, (Na,K) (sub 2) Mg(Si,Al) (sub 18) O (sub 36) (OH).9H (sub 2) O , of the zeolite group; transparent to translucent, vitreous to pearly; in spherical aggregates of thin, blade-shaped crystals at Kamloops Lake, BC, Canada and Leavitt Lake, CA.


See: laihunite.


Containing iron. Syn: ferruginous.


a. Unbalanced orientation of magnetic moments. Intermediate between ferromagnetism and antiferromagnetism.

b. Strong magnetic susceptibility caused by the overlap of adjacent d and p orbitals resulting in an unequal number of electrons aligned with spins antiparallel; e.g., magnetite, pyrrhotite, and maghemite. CF: antiferromagnetism; diamagnetism; ferromagnetism; paramagnetism; superexchange.


A possibly orthorhombic mineral, Fe (sub 2) (super 3) (Mo (super 6) O (sub 4) ) (sub 3) .8H (sub 2) O ; forms yellow earthy powder, incrustation, or silky, fibrous, and radiating crystals from reaction of pyrite with molybdenite under supergene conditions; relatively common in porphyry copper deposits of Southwestern United States in old mine dumps with jarosite and goethite. Syn: molybdic ocher; iron molybdate; molybdite.


A trigonal mineral, Na (sub 3) Fe(SO (sub 4) ) (sub 3) 3H (sub 2) O ; vitreous; soft; in the Atacama Desert, northern Chile. Formerly called ferronatrite.


An orthorhombic mineral, Li(Fe,Mn)PO (sub 4) ; forms a series with sicklerite; an alteration product of weathered triphyllite-lithiophilite in granite pegmatites, Keystone and Custer districts, Black Hills, SD; also Varutriisk, Sweden.


An amorphous mineral, Fe (sub 3) (AsO (sub 4) ) (sub 2) (OH) (sub 3) .5H (sub 2) O ; occurs with erythrite and annabergite at Cobalt, ON, Canada.


a. Native iron, such as the terrestrial iron from Disko Island, Greenland.

b. A general term applied to grains, scales, and threads of unidentifiable, more or less transparent or amorphous, red, brown, or yellow iron oxide in the groundmass of a porphyritic rock (Johannsen, 1939). CF: opacite. Syn: ferrospinel. c. A term used by Tieje (1921) for a cemented iron-rich sediment whose particles do not interlock.


The metasomatic alteration of other minerals into ferrite.


An isometric mineral, (K,Ca,Na)(W (super 6) ,Fe (super 3) )(O,OH) (sub 6) .H (sub 2) O ; in minute yellow octahedra and platy aggregates; in Uganda, Rwanda, Zaire, Portugal, France, Washington, and Nevada. Syn: tungstic ocher.


A variety of crystallized turquoise containing 5% Fe (sub 2) O (sub 3) ; from Lynchburg, VA.


A monoclinic mineral, Ca (sub 2) (Fe (super 2+) ,Mg) (sub 5) Si (sub 8) O (sub 22) (OH) (sub 2) ; amphibole group; has Mg/(Mg+Fe (super 2+) ) = 0 to 0.5; forms a series with tremolite and actinolite. Formerly called ferrotremolite.


An alloy of iron and one or more other elements useful for making alloy additions in steel or ironmaking.


A monoclinic mineral, NaCaFe(Fe,Mn) (sub 2) (PO (sub 4) ) (sub 3) ; alluaudite group; forms a series with alluaudite; in granite pegmatites.

ferroan dolomite

a. Dolomite having up to 20% of magnesium replaced by iron or manganese.

b. A mineral composition intermediate between those of dolomite and ankerite.

ferroan spinel

See: ceylonite.


A hypothetical composition, (Mg,Fe) (sub 3) Si (sub 2) O (sub 5) (OH) (sub 4) , used to describe chlorite compositions; intermediate to antigorite and greenalite.


A boron iron alloy containing 12% to 14% boron.


An orthorhombic mineral, (Fe,Mg)Al (sub 2) Si (sub 2) O (sub 6) (OH) (sub 4) ; forms series with carpholite and magnesiocarpholite; dark green; in quartz veins near Tomata, Celebes Island, Indonesia.


An alloy of iron and chromium.


See: copiapite.


A monoclinic mineral, Na (sub 3) (Fe (super 2+) ,Mg) (sub 4) AlSi (sub 8) O (sub 22) (OH) (sub 2) ; amphibole group; has Mg/(Mg+Fe (super 2+) ) = 0 to 0.49; forms a series with eckermannite.


A monoclinic mineral, NaCa (sub 2) (Fe,Mg) (sub 5) [Si (sub 7) AlO (sub 22) ](OH) (sub 2) ; amphibole group; has Mg/(Mg+Fe) = 0 to 0.49; forms a series with edenite.


Spontaneous electrical polarization with all dipoles in the same direction. The polarity can be reversed by an external electrical field.


See: barbosalite.


A gabbro in which the pyroxene or olivine, or both, are exceptionally high in iron.


A monoclinic mineral, FeSO (sub 4) .6H (sub 2) O ; hexahydrite group; transparent; forms at Vesuvius, Italy, as fine acicular crystals that are unstable under normal atmospheric conditions.


A mineral in the olivine series composed of 70% to 90% fayalite and 30% to 10% forsterite.


See: ferrosilite.


Black iron slag, said to be satisfactory for fashioning into gemstones.


Containing iron and magnesium. Applied to certain dark silicate minerals, esp. amphibole, pyroxene, biotite, and olivine.

ferromagnesian mineral

Any mineral having a considerable portion of iron and magnesium in its composition. CF: ferrous mineral.

ferromagnetic material

a. Material that in general exhibits the phenomena of hysteresis and saturation and whose permeability is dependent on the magnetizing force. Microscopically, the elementary magnets are aligned parallel in volumes called domains. The unmagnetized condition of a ferromagnetic material results from the overall neutralization of the magnetization of the domains to produce zero external magnetization.

b. The three substances, iron, nickel, and cobalt, are so considerably more magnetic than any other substances that they are grouped by themselves; they are termed ferromagnetic.


a. Spontaneous magnetic orientation of all magnetic moments in the same direction. The orientation can be reversed by an external magnetic field.

b. Strong magnetic susceptibility caused by overlap of adjacent d orbitals; e.g., iron, nickel, cobalt, and numerous alloys, both ferrous and nonferrous. CF: antiferromagnetism; ferrimagnetism.


A ferroalloy containing about 80% manganese and used in steelmaking.


A molybdenum-iron alloy produced in the electric furnace or by a thermite process. It is used to introduce molybdenum into iron or steel alloys and as a coating material on welding rods.


See: hedenbergite.


An orthorhombic mineral, FeSe (sub 2) ; marcasite group; occurs with chalcopyrite and pyrite as a cement in sandstones in the Tuva, Siberia, Russia.


Alloy of iron and silicon.


An orthorhombic mineral, (Fe,Mg) (sub 2) Si (sub 2) O (sub 6) ; pyroxene group; dimorphous with clinoferrosilite; forms a series with enstatite. Symbol, Fs. Formerly called iron hypersthene; orthoferrosilite. Syn: ferrohypersthene.


A synthetic ferrimagnetic substance having spinel structure, containing iron; conducts electricity poorly. See also: ferrite; hercynite.


A monoclinic mineral, Ca (sub 2) (Fe,Mg) (sub 3) Al (sub 2) (Si (sub 6) Al (sub 2) )O (sub 22) (OH) (sub 2) ; amphibole group, with Mg/(Mg + Fe) = 0 to 0.49; forms a series with tschermackite; a fairly common constituent of eclogites and amphibolites.


a. The term or prefix used to denote compounds or solutions containing iron in which iron is in the divalent (+2) state.

b. Of, relating to, or containing iron.

ferrous metallurgy

The metallurgy of iron and steel.

ferrous metals

A classification in the United States of metals commonly occurring in alloys with iron, such as chromium, nickel, manganese, vanadium, molybdenum, cobalt, silicon, tantalum, and columbium (niobium).

ferrous mineral

Any mineral having a considerable portion of iron in its composition. CF: ferromagnesian mineral.

ferrous oxide

This lower oxide, FeO, tends to be formed under reducing conditions; it will react with SiO (sub 2) to produce a material melting at about 1,200 degrees C, hence the fluxing action of ferruginous impurities present in some clays if the latter are fired under reducing conditions. Melting point, 1,420 degrees C; sp gr, 5.7.


An alloy of iron and vanadium.


A sintered oxide consisting mainly of the oxide BaFe (sub 12) O (sub 19) ; used for the production of permanent magnets.


An orthorhombic mineral, NaBF (sub 4) ; forms minute crystals with sassolite as a sublimate around fumaroles at Mt. Vesuvius, Italy.


a. Said of a sedimentary rock cemented with iron-bearing minerals, generally limonite; also, said of the iron-bearing cement.

b. To stain a rock with an iron-bearing compound.


a. Pertaining to or containing iron; e.g., a sandstone that is cemented with iron oxide. CF: ferriferous.

b. Said of a rock having a red or rusty color due to the presence of ferric oxide (the quantity of which may be very small).

ferruginous chert

A sedimentary deposit consisting of chalcedony or of fine-grained quartz and variable amounts of hematite, magnetite, or limonite.

ferruginous ores

Gangue; principally oxides, silicates, or carbonates of iron.

ferruginous rock

Rocks of this group are usually carbonate of iron that has partially or wholly replaced limestone.

ferruginous sandstone

A sandstone containing iron oxide as the cementing material, as grains, or both.

Fersman's law

Parallel orientation of feldspar prism edges with the edge between two adjacent rhombohedral planes of quartz in graphic granite so that the c axis of the quartz forms an angle of 42 degrees 16' with the c axis of the feldspar.


An orthorhombic mineral, (Ca,Ce,Na)(Nb,Ta,Ti) (sub 2) (O,OH,F) (sub 6) ; weakly radioactive; in syenites, may be associated with pyrochlore, alkali hornblende, apatite, sphene, magnetite, zircon, xenotime, or allanite; also in some marbles with columbite and monazite.


See: davidite.


A monoclinic mineral, Fe (sub 4) (VO (sub 4) ) (sub 4) .5H (sub 2) O ; golden brown; in uranium-vanadium deposits of the Colorado Plateau.

Fery radiation pyrometer

An instrument in which heat radiated from the hot body is focused, by means of a concave mirror, on a small central hole behind which a small thermocouple is placed in front of two small, inclined mirrors. The instrument is sighted onto the hot body and focused by rotating a screw until the lower and upper halves of the image coincide; the electromotive force generated by the thermocouple is indicated on a galvanometer. The instrument, once focused, gives continuous readings and may be connected to a recording indicator.