Appendix:Dictionary of Mining, Mineral, and Related Terms/P/5

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Set in motion or operated by compressed air.

pneumatic blowpipe

A long, 3/4-in-diameter (1.9-cm-diameter) metal pipe, connected to an air supply; used to blow out dust and chippings from vertical blast holes at quarries. The blowpipe is generally used for holes exceeding about 12 ft (3.66 m) deep. A stream of water is sometimes used instead of an air jet.

pneumatic caisson

Closed casing in which air pressure is maintained equal to the pressures of the water and soils on the outside. The deeper the caisson, the higher the pressure that must be maintained.

pneumatic cartridge loader

A cartridge loader widely used for underwater blasting, for blasting without removing the overburden, and for long-hole blasting. It is also being used increasingly for tunneling and other sorts of rock blasting.

pneumatic cleaning

Mineral cleaning by machines that utilize air currents as the primary separating medium. The air machines can generally be divided into three types: (1) pneumatic jigs, in which the air current is pulsated; (2) pneumatic tables, in which the refuse is diverted from the direction of flow of the clean mineral by a system of riffles fixed to the deck; and (3) pneumatic launders, in which the products are flowing in the same direction, and the clean mineral is skimmed off the top of the bed and/or the refuse is extracted from the bottom in successive stages.

pneumatic concentrator

Gravity jig, shaking table, or other device in which suitably ground minerals are separated by gravity during their exposure to a continuous or pulsating current of air.

pneumatic conveying

Use of compressed air to move fairly fine aggregates laterally and/or vertically.

pneumatic conveyor

a. A pipe or tube through which granular material is transported by airblast. It is used for pulverized coal, crushed rock (pneumatic stowing), cement, etc. The term could also be applied to a conveyor operated by compressed air.

b. An arrangement of tubes or ducts through which bulk material or objects are conveyed in a pressure and/or vacuum system.

pneumatic drill

Compressed-air drill worked by reciprocating piston, hammer action, or turbo drive.

pneumatic drill leg

See: air-leg support.

pneumatic filling

A filling method in which compressed air is utilized to blow filling material into a mined-out stope.

pneumatic flotation cell

Machine in which the air used to generate a mineralized froth is blown into the cell, either through a porous septum at or near the bottom, or by pipes that bring low-pressure air to that region.

pneumatic friction clutch

This clutch transmits power through friction shoes carried on the tube of cord and rubber construction. The pneumatic clutch is self-adjusting for wear owing to the natural resilience of the rubber tube. Disengagement is complete and automatic when the air under pressure is released. The clutch is controlled by finger pressure on a valve. The valve can be installed at the place most convenient for the operator.

pneumatic hammer

A hammer that uses compressed air for producing the impacting blow.

pneumatic hoist

A device for hoisting; operated by compressed air.

pneumatic injection

A method for fighting underground coal fires. This air-blowing technique involves the injection of an incombustible mineral, like rock wool or dry sand, through 6-in (15.2-cm) boreholes drilled from the surface to intersect underground passageways in the mines.

pneumatic jig

a. Air jig used in desert countries for concentrating ore.

b. A jigging machine in which an airblast performs the work of separation of minerals. c. See: Kirkup table; plunger jig washer.

pneumatic lighting

a. Underground lighting produced by a compressed-air turbomotor driving a small dynamo.

b. The use of compressed air to generate electric light. See also: air turbolamp.

pneumatic lubricator

See: line oiler.

pneumatic method

In flotation, a method in which gas is introduced under slight pressure near the bottom of the flotation vessel, the device used for introduction being either a submerged pipe or a porous cloth, frit, or rubber surface forming the wall of a wind box.

pneumatic mortar

Mortar applied to a surface with a cement gun in the same manner as gunite. Such mortar has a cube crushing strength of 3,000 psi (20.7 MPa) at 7 days and of 6,000 psi (41.4 MPa) at 28 days, with a water-cement ratio of 0.45.

pneumatic pick

A compressed-air-operated hand tool used to excavate coal, ore, and rock, with a punching action. Without the pick steel, its length is about 18 in (46 cm) and weight about 24 lb (10.8 kg). It delivers about 2,500 blows/min. The latest type is the water-controlled pick, so designed that the air valve is operated by water pressure. The water assists in suppressing the dust made during cutting.

pneumatic ram

A ram fed by a compressed-air pipeline. The piston is about 8 in (20 cm) in diameter, giving an area of 50 in (super 2) (323 cm (super 2) ) and exerts a pushing force of up to 4,000 lb (1,800 kg).

pneumatic riveter

A compressed-air tool used for driving rivets. See also: rivet.

pneumatic rod puller

An air-driven rod puller. See also: rod puller.


The branch of physics that deals with the mechanical properties of gases, such as their pressure, elasticity, density, and also of pneumatic mechanisms; sometimes it includes acoustics.

pneumatic shaft sinking

a. Shaft sinking with the aid of a drop shaft fitted with an air-tight deck to form a working chamber. See also: manlock.

b. The caisson-sinking process now largely obsolescent in mining practice.

pneumatic stowing

A system of filling mined cavities in which crushed rock is carried along a pipeline by compressed air and discharged at high velocity into the space to be packed, the intense projection ensuring a very high density of packed material. For stowing shallow workings--up to 200 yd (183 m) in depth--the stowing plant may be installed on the surface. The air pressure is about 60 psi (414 kPa). For deeper workings, the plant may be installed underground, and the crushed rock taken down from the surface. The stowing pipes are about 5 to 6 in (approx. 13 to 15 cm) in diameter. The system is often employed if important surface structures require protection. The material used is from old dirt heaps, screen dirt, and washery rejects. The material is crushed to -2-1/2 in (-6.35 cm) and preferably without the -1/2-in (-1.27-cm) material. See also: air-stowing machine; crusher stower; hydraulic stowing; low-pressure air stower.

pneumatic table

An appliance for the dry cleaning of ore or coal. It consists of a perforated deck, with vertical ribs or riffles, which is reciprocated; the motion keeps the bed of raw coal sufficiently mobile for the blast of air from below to effect a process of stratification (or layering). The coal rises to the surface, with dirt at the base and a central layer of middlings. See also: Birtley contraflow separator; Kirkup table; Vee table; air table.

pneumatic tamper

Essentially a long-stroke piston with a mushroom-shaped foot about 4 in (10 cm) in diameter. It operates on compressed air, which is used to lift the piston and footpiece; their combined weight, in falling, supplies the impact.

pneumatic tool

Tool operated by air pressure.

pneumatic transport

System composed of: a compressor, which provides airflow; a feeder, which meters the flow of material into a pipeline; and the pipeline-- for transporting coarse, dry, noncohesive material.

pneumatic water barrel

A special type of water barrel for removing water from a shaft sinking. By means of a hose connection to an air pump at the surface, a partial vacuum is created inside the barrel and the water lifts the valve and fills the barrel. The hose is then detached and the barrel is hoisted to the surface and discharged. Also called vacuum tank.


Said of a rock or mineral deposit formed by a gaseous agent. CF: hydatogenic; hydatopneumatogenic; pneumatolytic.


Alteration of a rock or crystallization of minerals by gaseous emanations derived from solidifying magma. Adj: pneumatolytic.


A term used in different connotations by various authors and perhaps best abandoned. It has been used to describe: (1) the surface effects of gases near volcanoes; (2) contact-metamorphic effects surrounding deep-seated intrusives; (3) that stage in igneous differentiation between pegmatitic and hydrothermal, which is supposed to be characterized by gas-crystal equilibria; and (4) very loosely, any deposit containing minerals or elements commonly formed in pneumatolysis, such as tourmaline, topaz, fluorite, lithium, and tin, and hence presumed to have formed from a gas phase. CF: pneumatogenic.

pneumatolytic metamorphism

Contact metamorphism in which the composition of a rock has been altered by introduced gaseous magmatic material.

pneumatolytic stage

That stage in the cooling of a magma during which the solid and gaseous phases are in equilibrium.


A combining form taken from the Greek meaning lung, and used in connection with the terminology of geologic processes and effects involving gases and vapors.


A disease of the lungs caused by habitual inhalation of irritant mineral or metallic particles. It occurs in any workplaces where dust is prevalent, such as mines, quarries, foundries, and potteries. Also called miner's asthma; miner's consumption; miner's lung. Also spelled pneumonoconiosis; pneumonokoniosis. CF: anthracosis; silicosis. See also: phthisis.


See: pneumoconiosis.


a. A localized enrichment; a crevice in bedrock containing gold; a rich patch of gold in a reef.

b. A rich deposit of mineral, but not a vein. c. A bin, of a capacity equal to the skip, used at the shaft bottom of an underground mine for quick and accurate skip loading. See also: shaft pocket; measuring chute. d. A receptacle, from which coal, ore, or waste is loaded into wagons or cars. e. A ganister quarryman's local term for masses of rock, 30 to 50 ft (9.1 to 15.2 m) in width, that are worked out and loaded, leaving buttresses of untouched rock between them to support the upper masses. f. A hole or depression in the wearing course of a roadway. g. A local accumulation of gas. h. A bulge, sop, or belly in a lode or bed. See also: belly. i. A cavity, whether filled with air, water, mineral, or gravel. j. In pegmatites, the central openings lined with crystals, including those of gem species.

pocket-and-fender method

In pillar extraction, a method in which lifts are mined in the same way as in the open-end method, except that a fender of coal or a series of small coal stumps is left adjacent to the gob as the lift is advanced. After the lift is completed, the fender or stumps of coal are blasted, and sometimes part of this coal is recovered.

pocket-and-stump method

A method of mining pillars in which a narrow pillar of coal, called the stump, is left along the goaf (worked-out space) to support the roof while driving the pocket. This coal acts as a protection for the miners. When the pocket has been completed, the stump is worked back, then another pocket is driven, and so on.

pocket compass

A magnetic needle enclosed in a nonmagnetic case, the needle being free to swing over a graduated face or dial. The compass is useful for experimental purposes or for direction-finding in desolate parts of the countryside, or during darkness and foggy weather.

pocket conveyor

A continuous series of pockets, formed of a flexible material festooned between crossrods, carried by two endless chains or other linkage that operate in horizontal, vertical and inclined paths.

pocket hunter

California. A miner or prospector who searches for small gold deposits which occur on the surface in the gold-bearing areas of the State.

pocket of gas

A small accumulation of methane in a roof cavity, where it is beyond the reach of the ventilating air current. See also: deflector sheet; combustible gases layer; hurdle sheet.

pocket transit

See: Brunton compass.


A rudely cylindrical orebody that decreases at the ends like a cigar or a potato. See also: lens.


See: Podzol.


A great soil group in the 1938 classification system; a group of zonal soils having an organic mat and a very thin organic-mineral layer overlying a gray, leached A2 horizon and a dark brown, illuvial B horizon enriched in iron oxide, alumina, and organic matter. It develops under coniferous or mixed forests or under heath, in a cool to temperate moist climate. Also spelled Podsol. Spelled "podzol" when used as the soil type belonging to the Podzol group. Etymol: Russian podsol, ash soil.


The process by which a soil becomes more acid owing to depletion of bases, and develops surface layers that are leached of clay and develop illuvial B horizons; the development of a podzol. Also spelled: podsolization.


The original spelling of poikilitic. Now obsolete in American usage, it is still the most accepted European spelling.

Poetsch process

a. The original freezing process of shaft sinking developed by F. H. Poetsch in 1883. See also: freezing method.

b. A process in which brine at subzero temperature is circulated through boreholes to freeze running water through which a shaft or tunnel is to be driven during development of a waterlogged mine.


See: poikilitic.


An automatic weighing device for use on belt conveyors. The device feeds the material from a hopper in a uniform stream onto a short independent belt conveyor and from there onto the main belt or bin. The weight of material on the measuring belt actuates a scale beam that raises or lowers a gate controlling the rate of flow from the feed hopper to a certain predetermined load per foot of measuring belt. A meter records the travel of measuring belt, and this figure multiplied by the weight per foot of belt, as fixed by the scale beam adjustment, gives the weight of material handled in any given period. See also: weightometer.


See: bornite. Also called poikgopyrite.


A rock texture in which numerous grains of various minerals in random orientation are completely enclosed within a large, optically continuous crystal of different composition. Also spelled poicilitic. CF: ophitic.

poikilitic texture

See: poikilitic.


a. Said of a metamorphic texture in which small grains of one constituent lie within larger metacrysts. Modern usage favors this meaning. Syn: sieve texture.

b. Said of a metamorphic texture due to the development, during recrystallization, of a new mineral around numerous relicts of the original minerals, thus simulating the poikilitic texture of igneous rocks. CF: helicitic.


a. A predetermined direction for driving a roadway underground. The point is fixed by roof plugs in the roadway. See also: alignment; spad.

b. One one-hundredth (0.01) part of a carat. When less than one carat, the weight of a diamond is usually expressed in points; e.g., 20 points equals 1/5 carat. c. A pipe through which steam or hot water is brought into contact with frozen gravel to thaw it for mining or dredging. d. See: well point. e. In quarrying, a type of wedge that tapers to a narrow, thin edge. f. The end or bottom of a borehole, as distinguished from the mouth or collar. g. A tool used in trimming and smoothing rough stone surfaces. h. Either of a pair of tapered rails at a turnout that can be adjusted to direct a set of mine cars from a straight rail track to another track branching off at an angle. See also: catch point; turnout.

point agate

See: point chalcedony.

point chalcedony

White or gray cryptocrystalline quartz flecked with tiny spots of iron oxide, giving the whole surface a uniform soft red color. Syn: point agate.

point defect

A deviation from ideal crystal structure about a point location; e.g., interstitial, atom missing (Schottky), or combined (Frenkel). CF: crystal defect; Frenkel defect; Schottky defect.

point driver

In metal mining, a person who drives steam or water points (specially made pipes with a chisel bit at one end) into the frozen ground of a placer deposit in advance of dredging operations, to thaw the ground so that it can be worked by the dredge for recovery of gold. Syn: thawing.

pointed box

A box, in the form of an inverted pyramid or wedge, in which minerals, after crushing and sizing, are separated in a current of water. See also: spitzkasten.

point group

One of 32 geometrically possible arrays of symmetry elements intersecting at a point. These symmetry elements are axes of rotation, both proper and improper (1 = i, 2 = m). All minerals having the symmetry of one point group belong to the same crystal class. CF: symmetry; crystal class; space group.

point kriging

Estimating the value of a point from a set of nearby sample values using kriging. The kriged estimate for a point will usually be quite similar to the kriged estimate for a relatively small block centered on the point, but the computed kriging standard deviation will be higher. When a kriged point happens to coincide with a sampled location, the kriged estimate will equal the sample value. See also: kriging.

point of attack

See: portal.

point of compound curvature

The point of tangency common to two curves of different radii, the curves lying on the same side of the common tangent. Abbrev., P.C.C.

point of curvature

The point where the alignment changes from a straight line or tangent to a circular curve; i.e., the point where the curve leaves the first tangent. Abbrev., P.C.

point of decalescence

See: decalescence.

point of frog

The intersection gagelines of the main track and a turnout.

point of intersection

a. The point where intersecting lines cross one another.

b. The point where the two tangents to a circular curve intersect. Abbrev., P.I. Also called vertex.

point of recalescence

See: recalescence.

point of switch

That point in the track where a car passes from the main line onto the rails of a turnout.

point of tangency

The point where the alignment changes from a circular curve to a straight line or tangent; i.e., the point where the curve joins the second tangent. Abbrev., P.T.

point plotting

In seismology, a procedure in reflection interpretation in which depth points are computed and plotted for each seismogram trace separately.

point source

A single point from which light emanates; e.g., the sun or a lamp filament, or their reflections. In the case of multiple reflections, each is a point source.


a. The unit of absolute viscosity, equal to one dyne-second per square centimeter. Named from the physicist Poiseuille.

b. The second unit of fluid viscosity, often expressed in centimeters or grams. See also: absolute viscosity; Poiseuille's law.

Poiseuille's law

A statement in physics that the velocity of flow of a liquid through a capillary tube varies directly as the pressure and the fourth power of the diameter of the tube and inversely as the length of the tube and the coefficient of viscosity. See also: poise.


a. In ion-exchange terminology, loading of resin sites with unwanted ions, thereby eliminating them as locations for loading.

b. Fouling of an organic solvent used in stripping pregnant leach liquor.

Poisson's ratio

The ratio of the lateral unit strain to the longitudinal unit strain in a body that has been stressed longitudinally within its elastic limit. It is one of the elastic constants. Symbol: sigma . CF: modulus of incompressibility.

poker man

A laborer who removes blue powder and ash residue from retorts after molten zinc has been tapped. Also called scraper.


a. Lacking a center of symmetry, with the result that crystals are acentric in their crystal forms and physical properties; i.e., electrostatic or magnetic properties are equal and opposite at the opposite ends of these crystals; e.g., tourmalines. Ant. nonpolar.

b. An optical device, such as nicol prism or polarizing filter, for the production of plane-polarized light. See also: nicol; Nicol prism.

Polar Ajax

A high-strength, high-density, nitroglycerin gelatin explosive, supplied in both unsheathed and sheathed forms. See also: Ajax.

polar curve

A graph showing the distribution of light in a flame safety lamp obtained by plotting the values obtained at intervals of 10 degrees around a full circle.

polar explosive

Explosive containing an antifreeze ingredient and distinguished by the prefix polar. Polar and nonpolar explosives of equal grade possess similar characteristics. Explosives that contain nitroglycerin tend to freeze when stored at low temperatures for lengthy periods. Syn: low-freezing explosive.


An optical device consisting of two polarizers with a space between for a crystal or rock under study. Syn: stauroscope.


In crystallography, the property of having differing types of termination at the two ends of a prismatic crystal. May be reflected in pyroelectric properties, conduction of electric current, etc.


The property of an ion or atom to deform so as to create a dipole from the displacement of its electron cloud.


a. The difference between the equilibrium value of the potential of an electrode and the value attained when an appreciable current flows through a system.

b. In electrolysis, the condition in the vicinity of an electrode, such that the potential necessary to get a desired reaction is increased beyond the reversible electrode potential. c. The production of dipoles or higher-order multipoles in a medium. d. The polarity or potential near an electrode. e. In seismology, the direction of particle motion of shear (S) waves in a plane perpendicular to the direction of propagation. f. A process of filtration or reflection by which ordinary light is converted to plane-polarized light in which the electric vector of a light ray is confined to a single plane.

polarized light

Light with its electric vector restricted to a plane or to an elliptically or circularly helical path as a result of filtration, reflection, or interaction with a crystal structure.


In a polarized-light microscope, the polarizing filter or Nicol prism (polar) located below the sample stage. See also: nicol; analyzer.

polarizing prism

A prism of an anisotropic crystal, commonly calcite, cut and cemented together so as to permit passage of one of the doubly refracted light rays while reflecting the other out of the train of a microscope. Syn: Nicol prism.

polar moment of inertia

The second moment of area about an axis perpendicular to its plane is known as the polar moment of inertia of a plane section. See also: moment of inertia.


A sheet of cellulose impregnated with optically aligned crystals of quinine iodosulfate, which permit passage of light with its electric vector in one plane while absorbing all other impinging light. It is a cheap substitute for Nicol prisms in modern polarized-light microscopes.

Polar Viking

A typical nitroglycerin powder explosive, which is now supplied only in the sheathed form.


Dutch. Low fertile land, as in The Netherlands and Belgium, reclaimed from the sea by systems of dikes and embankments.


a. Either of the two regions of a permanent magnet or an electromagnet where most of the lines of induction enter or leave. A point toward which a freely suspended ferromagnetic rod aligns itself.

b. The negative or positive electrical pole in a circuit.

pole chain

A surveyor's chain. See also: Gunter's chain.

pole figure

A stereographic projection representing the statistical average distribution of poles of a specific crystalline plane in a polycrystalline metal, with reference to an external system of axes. In an isotropic metal; i.e., in one having a completely random distribution of orientations, the pole density is stereographically uniform; preferred orientation is shown by an increased density of poles in certain areas.


See: locomotive brakeman.

pole piece

A specially shaped piece of magnetic material forming an extension to a magnet; e.g., the salient poles of a generator or motor.

pole strength

In measurement of magnetic strength, the number of unit poles in the measured field. One unit pole is the strength in a vacuum required to exert 1 dyn in a 1-cm gap between poles.


A steel-gray dioxide of manganese, MnO (sub 2) , crystallizing in the tetragonal system. It is distinguished from pyrolusite by its hardness and anhydrous character.


a. The act or process of temporarily protecting the face of a level, drift, cut, etc., by driving poles or planks along the sides of the yet unbroken ground. Used esp. for holding up soft ground. See also: forepoling. Also called spiling.

b. A step in the fire refining of copper to reduce the oxygen content to tolerable limits by covering the bath with coal or coke and thrusting greenwood poles below the surface. There is a vigorous release of reducing gases that combine with the oxygen contained in the metal. If the final oxygen content is too high, the metal is underpoled; if too low, overpoled; and if just right, tough pitch.

poling back

Carrying out excavation behind timbering already in place.

poling board

a. A forepoling board, driven horizontally ahead to support the roof when tunneling through running ground. See also: forepoling.

b. In trenching, either of a pair of side boards wedged apart.


Tripoli slate. Also called polishing slate.


An attribute of surface texture of a rock, characterized by high luster and strong reflected light, produced by agents, such as desert or glacial polish, or by artificial grinding and smoothing; e.g., marble or granite.

polished section

A slice of rock or mineral that has been highly polished for examination by reflected-light or electron microbeam techniques, a procedure mostly applied to opaque minerals. See also: thin section; reflected-light microscope.

polished surface

See: slickensides.


Removing the last traces of suspended matter from solutions by passing them through a filter coated with diatomaceous earth or similar material.

polishing cask

A barrel in which grained gunpowder is tumbled with graphite to glaze it.

polishing mill

A lap of metal, leather, or wood used by lapidaries in polishing gems.

polled stone

Som. Stone hewn into shape and faced ready for building. Building stone with one side rough faced, as opposed to hammer-and-punch dressed.

pollen peat

Peat rich in pollen grains.

poll pick

A pick with a head for breaking away hard partings in coal seams or knocking down rock already seamed by blasting. See also: hammerpick.


An isometric mineral, (Cs, Na) (sub 2) Al (sub 2) Si (sub 4) O (sub 12) .H (sub 2) O ; zeolite group; forms a series with analcime; colorless; occurs in granite pegmatites; a source of cesium and a minor gemstone. Syn: pollux.


See: pollucite.


A prefix signifying many. Used in many mineral names, such as polybasite, polycrase, polyhalite, and polyaugite.


A mixture of argentite and tetrahedrite.


A monoclinic mineral (Ag,Cu) (sub 16) Sb (sub 2) S (sub 11) ; forms a series with pearcite; pseudohexagonal; soft; metallic; gray to black; sp gr, 6.0 to 6.2; in low-temperature veins; a source of silver.


Altered cordierite.


See: pleochroism.


See: cordierite.


An orthorhombic mineral, (Y,Ca,Ce,U,Th)(Ti,Nb,Ta) (sub 2) O (sub 6) ; black; in granite pegmatites. Formerly spelled polykras.


A mineral specimen composed of an assemblage of individual crystals of various crystallographic orientations. See also: glomerocryst; syntaxy.


An aggregate of crystals of the same species.


An isometric mineral, NiNi (sub 2) S (sub 4) ; linnaeite group; easily confused with violarite.


a. Resulting from more than one process of formation, derived from more than one source, or originating or developing at various places and times; e.g., said of a mountain range resulting from several orogenic episodes.

b. Consisting of more than one type of material, or having a heterogeneous composition; e.g., said of a conglomerate composed of materials from several different sources. CF: monogenetic.


A plane figure bounded by straight lines.


A two-dimensional form having more than four regular straight sides.

polygonal method

An ore-reserve computation method in which an assumption is made that the area of influence of each drill hole extends halfway to the neighboring drill holes. Therefore, thickness and grade must vary uniformly in opposite directions and in such cases errors tend to be compensating. Where the thickness and grade vary in the same direction, the errors will accumulate and cause erroneous results.


A triclinic mineral, K (sub 2) Ca (sub 2) Mg(SO (sub 4) ) (sub 4) .2H (sub 2) O ; bitter tasting; varicolored; occurs in salt deposits in Texas, New Mexico, and Germany.


See: polycrase.


a. A compound formed by the union of two or more molecules of the same simple substance.

b. In the plural use, compounds identical in composition but which vary in molecular weight, such as ethylene (ethene), Ch (sub 2) :Ch (sub 2) ; propylene (propene), CH (sub 3) CH:CH (sub 2) ; and butylene (butene), CH (sub 3) CH (sub 2) CH:CH (sub 2) .


Union of two or more molecules of given structure to form a new compound with the same elemental proportions but with different properties and a higher molecular weight.


To chemically combine small molecules into larger molecules; to undergo polymerization.

polymetallic sulfide

A sulfide deposit rich in copper, zinc, lead, silver, or gold, which forms as a result of hydrothermal activity in the vicinity of mid-ocean spreading centers or tectonically active basins. The first discovery of these deposits was from the French submersible Cyana, in 1979, during a joint international biological investigation of thermal springs on the deep seabed. The term derives from the French "sulfides polymetalliques."


An orthorhombic mineral, (Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O (sub 4) ; radioactive; in syenites and granite pegmatites. Also spelled polymignyte.


The characteristic of a chemical compound to crystallize in more than one crystal class; e.g.: (1) kyanite, andalusite, and sillimanite; (2) quartz, tridymite, cristobalite, coesite, and stishovite. Allotropy refers specif. to chemical elements crystallizing in more than one class; e.g., graphite, diamond, chaoite, and lonsdaleite. Polymorphism limited to two or three crystal classes is dimorphism or trimorphism, respectively. Individual species are polymorphs (dimorphs, trimorphs). Polytypism refers to variable stacking of identical layer structures in different crystal classes. Adj: polymorphic (dimorphic, trimorphic). Adv: polymorphous (dimorphous, trimorphous). Syn: pleomorphism. CF: dimorphism; trimorphism; isomorphism; isotypy; polysyngony. See also: allotropic.


Variety of nigritite found in a finely dispersed state in argillaceous rocks. CF: keronigritite; humonigritite.


A montmorillonoid clay mineral in soils.


In electricity, having or producing two or more phases, such as a polyphase current. Syn: multiphase.


Having a texture consisting of numerous small grains; said of minerals.


Minerals having a texture of many small grains.


A condition where two or more minerals have the same composition, but different crystal classes owing to changed bond angles; e.g., alpha and beta quartz. CF: polytypy; polytropy; polymorphism.

polysynthetic twinning

a. Two systems of lamellar twinning at an angle with one another.

b. Successive twinning of three or more individuals, according to the same twin law, with parallel composition planes; commonly revealed by visibly striated cleavage planes; e.g., albite twinning in plagioclase feldspar. CF: cyclic twinning; twin laminae.

polythionic acid

Any of several acids in a series related to sulfurous and thiosulfuric acid.


A condition in which there is no change in the geometrical symmetry of the crystal structure of two related minerals, but a change to permit a variant in the resultant mineral; e.g., orthoclase microcline. CF: polytypy; polysyngony.


a. A condition in micas and similar clay minerals in which they show growth spirals which are due to lamellae of different orientations.

b. One-dimensional polymorphism resulting from alternate stacking of identical layers; e.g., kaolinite, nacrite, and dickite. Syn: polytypy.


A condition in which the space lattice of two related minerals is completely altered to a new type. This is illustrated by the quartz-tridymite relationship. See also: polytypism. CF: polysyngony; polytropy.

polyvinyl butyral

A resin, with a plasticizer. Provides the interlayer in standard laminated glass made from either polished plate glass or window glass.


A variety of native platinum alloyed with iron.

Poncelet wheel

A kind of undershot waterwheel suitable for falls of less than 6 ft (1.8 m), having the buckets curved so that the water presses on them without impact.

Ponsard furnace

A furnace in which the escaping combustion gases, passing through tubular flues, heat the incoming air continuously through the flue walls.


An iron rod used in glassmaking to carry and manipulate hot bottles, etc.; has a projection at the end, varying in shape according to the character of the ware carried. Also called snap; pontee; ponto; ponty; puntee; puntil; punty.


a. A float supporting part of a structure, such as a bridge.

b. A wood platform used to support machinery on soft ground.

pony set

A small timber set or frame incorporated in the main sets of a haulage level to accommodate an ore chute or other equipment from above or below.


a. To undercut or undermine material, such as coal, esp. in excavating.

b. A continuous area of porous sedimentary rock that yields petroleum or gas on drilling.

pool washing screen

A screen that is divided into alternate transverse screen cloth panels and metal plate pool sections. Water is directed to the pools, setting up a swirling motion that agitates fines into suspension. See also: vibratory screen.

poor fumes

Toxic or irritating chemicals produced by an explosion.

poorly sorted

See: nongraded sediment.


a. A short, secondary drill hole blasted to reduce larger pieces of rock or to trim a working face. Also called pophole; pop shot. See also: pop shot.

b. Explosion in sealed area of a mine. Manometers may record a sudden pressure rise due to such an explosion.

pop a boulder

To place and explode a stick of dynamite on a boulder so as to break it for easy removal from a mine.


A secondary drill hole. See also: pop.

pophole blasting

Breaking down large pieces of asbestos by means of short blastholes judiciously placed.

pop-off valve

A pressure-relief valve.


a. A pulley frame or the headgear over a shaft. A headframe.

b. A valve that lifts bodily from its seat instead of being hinged. See also: poppet valve; puppet valve.

poppet head

a. The top of a derrick where the pulley is situated.

b. See: headgear.

poppet valve

A valve shaped like a mushroom, resting on a circular seat, and opened by raising the stem. See also: poppet; puppet valve.


The drilling, charging, and firing of a hole in the center of a boulder at quarry and open-cast mines. The hole is charged at the rate of 2 to 3 oz (57 to 85 g) of explosive per yd (super 3) (74.2 to 111.3 g/m (super 3) ) of rock. The charge is pushed to the bottom of the hole and then filled with sand or soil. Also called pop shooting. See also: snakeholing.

poppy stone

Red orbicular jasper from California; popular for cutting en cabochon.


A method of drilling a hole just beyond the center of a boulder to be broken so that the charge is centrally situated. Stemming is used. Pop-shooting is economical in explosives, but drilling is required. It is somewhat difficult to control the throw of broken material, but there is little noise to cause annoyance to nearby property owners. See also: secondary blasting.

pop shot

a. In mining, a shot fired for trimming purposes.

b. In quarrying, a method of secondary blasting. c. A shot by which a boulder in a mine is broken up by placing a stick of dynamite on top of the boulder and exploding it. d. In blasting, an explosion of the charge that simply blows out the tamping. Syn: block hole shot. See also: pop.

pop valve

A pressure-relief valve.

porcelain clay

A clay suitable for use in the manufacture of porcelain; specif. kaolin.

porcelain earth

See: kaolinite.

porcelain jasper

A hard, naturally baked, impure clay or porcellanite that, because of its red color, was long considered a variety of jasper. See also: porcellanite.

porcelain oven

A firing kiln used in baking porcelain.


Resembling unglazed porcelain; e.g., said of a rock consisting of chert and carbonate impurities or of clay and opaline silica. Also spelled: porcellaneous; porcelanous.


A dense siliceous rock having the texture, dull luster, hardness, conchoidal fracture, and general appearance of unglazed porcelain; it is less hard, dense, and vitreous than chert. The term has been used for: an impure chert, in part argillaceous; an indurated or baked clay or shale often found in the roof or floor of a burned-out coal seam; and a fine-grained, acidic tuff compacted by secondary silica. Etymol: Italian porcellana, porcelain. Also spelled: porcelanite; porcelainite. See also: siliceous shale; porcelain jasper; haelleflinta.


A space in rock or soil not occupied by solid mineral matter. Syn: interstice; void.

pore pressure

See: neutral stress.

pore space

The open spaces or voids in a rock taken collectively. See also: porosity; permeability.

pore-space filling

The deposition of minerals in the voids of rocks or between the grains of loose sediment.

pore water

a. In soil technology, free water present in a soil. Normally under hydrostatic pressure. The shear strength of adjacent soil depends on this pore pressure, which reduces frictional resistance and soil stability.

b. Subsurface water in the voids of a rock. Syn: interstitial water.

pore-water pressure

See: neutral stress.


An instrument used to determine the porosity of a rock sample by comparing the bulk volume of the sample with the aggregate volume of the pore spaces between the grains. Porosimeters are of various designs, some using liquids and some using gases, at known pressures, to find the volume of openings.


a. The ratio, P, expressed as a percentage of the volume, Vp, of the pore space in a rock to the volume, Vr, of the rock, the latter volume including rock material plus the pore space; P = 100 Vp/Vr.

b. The amount of void space in a reservoir usually expressed as percent voids per bulk volume. Absolute porosity refers to the total amount of pore space in a reservoir, regardless of whether or not that space is accessible to fluid penetration. Effective porosity refers to the amount of connected pore spaces; i.e., the space available to fluid penetration. Syn: total porosity.

porosity coefficient

Evolved by Professor H. Briggs in 1931 to express the conductance of a waste to air leakage, per foot length of the roadway per foot width of the leakage zone.


Containing voids, pores, cells, interstices, and other openings, which may or may not interconnect. See also: porosity.

porous ground

Any assemblage of rock material that, as a result of fracturing, faulting, mode of deposition, etc., contains a high percentage of voids, pores, and other openings.

porous-pot electrode

Nonpolarizable electrode consisting of a metal bar immersed in a saturated electrolytic solution which is contained in a porous pot.


A native alloy of argentiferous gold with palladium, the palladium content varying up to 10%. From Porpez, Brazil. Syn: palladium gold.


An obsolete term synonymous with porphyry. The term was originally used to distinguish porphyries that contain plagioclase phenocrysts from those that contain alkali feldspar phenocrysts.


a. Said of the texture of an igneous rock in which larger crystals (phenocrysts) are set in a finer-grained groundmass, which may be crystalline or glassy or both. Also, said of a rock with such texture, or of the mineral forming the phenocrysts.

b. Pertaining to or resembling porphyry.

porphyritic obsidian

Volcanic glass having microcrystalline phenocrysts.

porphyritic texture

See: porphyritic.


A pseudoporphyritic crystal in a rock produced by metamorphic recrystallization. Adj: porphyroblastic. Syn: metacrystal; pseudophenocryst.


a. Pertaining to the texture of a recrystallized metamorphic rock having large idioblasts of minerals possessing high form energy (e.g., garnet, andalusite) in a finer-grained crystalloblastic matrix.

b. See: pseudoporphyritic. CF: crystalloblastic.


A rock fragment contained in mylonite.

porphyroclastic structure

See: mortar structure.


Said of the texture of a diabase porphyry having phenocrysts of plagioclase and augite in a ground mass of plagioclase laths and augite.


Said of or pertaining to a blastoporphyritic or sometimes porphyroblastic metamorphic rock of igneous origin, or a feldspathic metasedimentary rock having the appearance of a porphyry. It occurs in the lower grades of regional metamorphism.


An igneous rock of any composition that contains conspicuous phenocrysts in a fine-grained groundmass; a porphyritic igneous rock. The term (from a Greek word for a purple dye) was first applied to a purple-red rock quarried in Egypt and characterized by phenocrysts of alkali feldspar. The rock name descriptive of the groundmass composition usually precedes the term; e.g., diorite porphyry. Obsolete syn: porphyrite.

porphyry copper deposit

A large body of rock, typically porphyry, that contains disseminated chalcopyrite and other sulfide minerals. Such deposits are mined in bulk on a large scale, generally in open pits, for copper and byproduct molybdenum. Most deposits are 3 to 8 km across, and of low grade (less than 1% Cu). They are always associated with intermediate to felsic hypabyssal porphyritic intrusive rocks. Distribution of sulfide minerals changes outward from dissemination to veinlets and veins. Supergene enrichment has been very important at most deposits, as without it the grade would be too low to permit mining.

porphyry deposit

a. A deposit in which minerals of copper, molybdenum, gold, or less commonly tungsten and tin, are disseminated or occur in a stockwork of small veinlets within a large mass of hydrothermally altered igneous rock. The host rock is commonly an intrusive porphyry, but other rocks intruded by a porphyry can also be hosts for ore minerals.

b. A deposit, usually of copper, molybdenum, or tin, in igneous rock of any composition that contains larger crystals in a fine-grained groundmass.


a. In drilling, a cylindrical opening through the bit shank from which the circulating fluid is discharged at the bit face into the water ways.

b. Any opening in a furnace through which fuel or flame enters or exhaust gases escape.

portable aggregate plant

A plant mounted so that it can be moved over the highways on its own mounting and that performs all the operations of a stationary plant, including crushing, scalping, secondary crushing, screening, washing, and sand separation. Some of these complete plants are mounted on one chassis; others have the more common operations on one chassis with the supplementary equipment on separate portable mountings.

portable bucket loader

Any of several types of self-propelled multibucket loaders that are considered suitable for miscellaneous light excavating work. These loaders dig their own path, and to do this, have various means of gathering the material to a point where it will be picked up by the buckets as they pass over the lower tumbler. While these loaders are usually used for reclaiming from stockpiles, they can, under favorable conditions, excavate from deposits. These machines always are mounted on crawler treads.

portable concentric mine cable

A double conductor cable with one conductor located at the center and with the other conductor strands located concentric to the center conductor with rubber or synthetic insulation between conductors and over the outer conductor. Syn: concentric mine cable.

portable conveyor

a. A conveyor designed to be moved as a unit. It is commonly wheel mounted and may or may not be sectional.

b. Any type of transportable conveyor, usually having supports that provide mobility. See also: boxcar loader; bucket loader; hatch conveyor; loading conveyor; movable conveyor; portable drag conveyor; roller conveyor; trimmer conveyor; unloading conveyor; wheel conveyor.

portable crane

A hoisting device carried by a frame mounted on wheels.

portable crusher

A crusher with temporary support foundations, so that it can be moved in sections, or it can be moved along roadways with minimum dismantling.

portable drag conveyor

A portable conveyor upon which endless drag chains are used as the conveying medium. Also a term sometimes applied to a portable flight conveyor. See also: drag-chain conveyor; portable conveyor.

portable drill

Any size drill outfit that is wheel-, skid-, or track-mounted so that it can be moved readily as a unit.

portable electric lamp

Self-contained lamp (such as a battery-operated lamp) that may be worn on the person or carried about freely.

portable flame-resistant cable

A portable cable that will meet the flame tests of the U.S. Mine Safety and Health Administration.

portable loader

A loading machine mounted on wheels or crawler tracks. See also: shovel loader.

portable mine blower

A motor-driven blower (fan) to provide secondary ventilation into spaces inadequately ventilated by the main ventilating system; the air is directed to such spaces through a duct.

portable mine cable

An extra-flexible cable used for connecting mobile or stationary equipment in a mine to a source of electric energy where permanent wiring is prohibited or impractical. (A portable cable for mining service is not always extra flexible and is used also with portable as well as with mobile and stationary equipment.)

portable parallel duplex mine cable

A double or triple conductor cable with conductors laid side by side without twisting, with rubber or synthetic insulation between conductors and around the whole. The third conductor, when present, is a safety ground wire.

portable pneumatic core sampler

A device developed by the U.S. Navy Ordnance Laboratory for sampling coral and sand bottoms. It consists of a four-legged pyramidal frame about 8 ft (2.4 m) high, a pneumatic hammer with air supply and exhaust hosing, 400 lb (180 kg) of lead weight, an anvil, and a 4-ft-long (1.2-m-long) aluminum barrel with a driving head for cutting through coral.

portable shunt

A tub-changing arrangement for a tunnel face. See also: double-track portable switch.

portable substation

See: transportable substation.

portable trailing cable

A flexible cable or cord used for connecting mobile, portable, or stationary equipment in mines to a trolley system or other external source of electric energy where permanent mine wiring is prohibited or is impractical.


Can. Trail between waterways.


a. The rock face at which tunnel driving is started. Syn: point of attack.

b. The surface entrance to a drift, tunnel, adit, or entry. c. The log, concrete, timber, or masonry arch or retaining wall erected at the opening of a drift, tunnel, or adit.

portal crane

A type of jib crane carried on a four-legged portal frame, which runs along rails. See also: goliath crane; platform gantry.


A term encountered in disputes over what constitutes compensable "working time" under Federal laws. Portal literally means "entrance" and, in underground coal mining, portal refers to the mine mouth or entry at the surface. Hence, portal-to-portal as a descriptive term means strictly elapsed time from entry through the portal to exit on return.

port crown

Port roof of a tank.

porte et gardin plow

See: scraper plow.


A long iron bar attached to a forging, or a piece in process of forging, by which to swing and turn it.


The opening or passageway connecting the inside of a bit or core barrel to the outside and through which the circulating medium is discharged.

Portland beds

See: Portland limestone.

portland cement

A calcium-aluminum silicate produced by fusing or clinkering limestone and clay in a kiln so as to drive off carbon dioxide and produce an oxide glass. The clinker is ground very fine and, when mixed with water, will recrystallize and set. It is combined with aggregate to form concrete. The name is from a resemblance to the Portland limestone of England.

portland cement mortar

A mixture of portland cement, sand, and water. See also: cement mortar.


A hexagonal mineral, Ca(OH) (sub 2) ; occurs in skarns; an important constituent of portland cement.

Portland limestone

A series of limestone strata, belonging to the Oolite group (Upper Jurassic) on the Isle of Portland, Dorsetshire, England. Most of the building stone used in London is from these quarries.

Portland stone

a. A yellowish-white, oolitic limestone from the Isle of Portland (a peninsula in southern England), widely used for building purposes.

b. A purplish-brown sandstone (brownstone) from Portland, CT.

portrait stone

A flat diamond, sometimes with several rows of facets around its edge; used for covering very small portraits.


An oxygenated hydrocarbon from the Great Western mercury mine, Lake County, CA. It occurs in plates and nodules, sometimes brittle, occasionally hard; the color is light green to reddish-brown; and sp gr, 0.85 to 0.985.

position block

Mining claim that is in a position to contain a lode if it continues in the direction in which it has been proved in other claims, but which itself has not been proved.


a. Electrically, a point at a relatively high potential with respect to another point. A positive ion is one in which a particle, molecular or atomic, has ceased to be neutral owing to loss of one or more electrons.

b. Positive ore is ore that has been proved to exist by being blocked out in panels sampled at close intervals on all four sides so as to establish its quality and quantity beyond reasonable doubt.

positive confining bed

The upper confining bed of an aquifer whose head is above the upper surface of the zone of saturation; i.e., above the water table. Little used.

positive crystal

An optically positive crystal.

positive derail

A device installed in or on a mine track to derail runaway cars or trips. This device is held open by a spring, necessitating that a worker hold it closed while a trip passes over it.

positive-discharge bucket elevator

A spaced bucket-type elevator in which the buckets are maintained over the discharge chute for a sufficient time to permit free gravity discharge of bulk materials. See also: bucket elevator.

positive displacement pump

regardless of the head against which it operates. See also: bladder pump.

positive drive

A driving connection in two or more wheels or shafts that will turn them at approx. the same relative speeds under any conditions.

positive element

A large structural feature or area that has had a long history of progressive uplift; also, in a relative sense, one that has been stable or has subsided much less than neighboring negative elements.

positive elongation

Tabular, lathlike, or needle crystals with the electric vector of their slow ray parallel to the long direction of the crystal. Syn: length slow. CF: negative elongation.

positive ore

a. Ore exposed on four sides in blocks of a size variously prescribed. Syn: ore developed. See also: developed reserve; proved ore.

b. Ore which is exposed and properly sampled on four sides, in blocks of reasonable size, having in view the nature of the deposit as regards uniformity of value per ton and of the third dimension, or thickness.

positive rake

The orientation of a cutting tool in a manner, so that the angle formed by the leading face of the tool and the surface behind its cutting edge does not exceed 90 degrees ; e.g., teeth in a ripsaw. Syn: gouge rake. See also: gouge angle CF: rake.

positive ray

Stream of positively charged atoms or molecules that take part in the electrical discharge in a rarefied gas. Positive rays have been studied by allowing them to pass through a perforated cathode onto a photographic plate, being deflected by magnetic and electrostatic fields (Thomson's parabola method) and by means of Aston's mass spectrograph. Syn: canal ray.

positive temperature coefficient

See: temperature coefficient.


Positive electron of the same mass as a negative electron; has only transitory existence.

possessio pedis

The actual possession of a mining claim by the first arrival.

possessory title

Title vested in the locator of a mining claim by compliance with the State and Federal mining laws.

possible crystal face

Any crystal face permitted by the symmetry of crystal structure but not appearing on a particular mineral specimen.

possible ore

An obsolete term for inferred reserves. See also: reserve. Syn: future ore.


a. To bring the survey, maps, and records of a mine up to date.

b. A charge of ore for a smelting furnace. c. Any of the distance pieces to keep apart the frames or sets in a shaft; a studdle. d. A mine timber, or any upright timber, but more commonly used to refer to the uprights which support the roof crosspieces. Commonly used in metal mines instead of leg which is the coal miners' term, esp. the in the Western United States. Syn: upright. e. A support fastened between the roof and the floor of a coal seam; used with certain types of mining machines or augers. f. A pillar of coal or ore. g. An item of kiln furniture. Posts, also known as props or uprights, support the horizontal bats on which ware is sent on a tunnel kiln car. h. A discrete portion of bond between abrasive grains in a grinding wheel or other abrasive article. When an abrasive grain held by a post has become worn, the post should break to release the worn grain so that a fresh abrasive grain will become exposed. i. A mass of slate traversed by so many joints as to be useless for building purposes. j. Any of the four vertical timbers of a square set.


A mode of working coal, in which a certain amount of coal is left as pillars and the remainder is taken away, forming rooms or other openings. The method is also called bord-and-pillar; pillar-and-breast; etc.

post brake

A type of brake sometimes fitted on a steam winder or haulage. It consists of two upright posts mounted on either side of the drum and operating on brake paths bolted to the drum cheeks. See also: winder brake.

post drill

An auger (or drill) supported by a post.

post hole

A shallow borehole.

post-hole auger

A hand-rotated drilling tool that enables bores to be sunk down to about 20 ft (6 m) in unsupported holes and deeper in cased holes. See also: shell-and-auger boring.

post-hole digger

Large auger, rotated mechanically or by hand, used for digging in unconsolidated ground and retrieving a sample.


In tectonics, said of a recurrence of forces and movement along lines or over areas affected by similar forces in a previous period; overprint.


York. Extracting the post or pillars; pillar robbing.

post jack

A jack for pulling posts. See also: post puller.

postmineral movement

Movement usually along a fault that occurs after a mineral has been deposited.

postorogenic intrusion

An igneous intrusion that took place after an orogenic event or cycle.

post puller

An electric vehicle having a powered drum for handling wire rope used to pull mine props after coal has been removed; used for the recovery of the timber.

post puncher

A coal-mining machine of the puncher type supported by a post.

post stone

An English term for any fine-grained sandstone or limestone. Also spelled: poststone.


a. A vessel for holding molten metal.

b. An electrolytic reduction cell used to make such metals as aluminum from fused electrolyte. c. Mud-filled stump of Sigillaria in an upright position in the roof of certain coal seams. The stump became hollow by decay of the central pithy part, the hollow being filled by mud. This stump is now a separate mass of shale and is liable for collaspse without warning. See also: caldron bottom; pot bottom. d. A colloquial syn. of seismic detector. e. See: abyss; line oiler.


A tetragonal mineral, PdHg ; silver white. Syn: palladium amalgam.


Potassium carbonate, K (sub 2) CO (sub 3) ; formerly extracted from wood ashes; used as a component of glasses, glazes, and enamels to enhance colorants. Also called pearl ash. Syn: potassium carbonate.

potash alum

See: kalinite; alum; potassium alum.

potash feldspar

See: potassium feldspar.

potash fixation

The retention of potassium in clays either by chemical combination in clay minerals or by adsorption.

potash mica

See: muscovite.

potash spar

See: potassium feldspar; spar. CF: soda spar.

potash syenite

A syenite with a large excess of potassium feldspar (microcline, orthoclase) or feldspathoid over sodium feldspar (albite).


Of, pertaining to, or containing potassium; relating to or containing potash.


A highly reactive metallic element of the alkali group; it is soft, light, and silvery. Symbol, K. Occurs abundantly in nature; obtained from the following minerals: sylvite, carnallite, langbeinite, and polyhalite. The greatest demand is for use in fertilizers.

potassium alum

An isometric mineral, KAl(SO (sub 4) ) (sub 2) .12H (sub 2) O . Syn: potash alum.

potassium aluminosilicate

See: feldspar.

potassium apatite

A synthetic phosphate with K replacing Ca.

potassium bentonite

A clay of the illite group, formed by the alteration of volcanic ash; a metabentonite. Syn: K-bentonite. See also: metabentonite.

potassium carbonate

See: potash.

potassium chloride

See: sylvite.

potassium feldspar

The minerals microcline, orthoclase, and sanidine. Syn: potash feldspar; potash spar; K-feldspar; K-spar.

potassium titanate

This compound, which approximates in composition to K (sub 2) Ti (sub 6) O (sub 13) and melts at 1,370 degrees C, can be made into fibers for use as a heat-insulating material.

potato stone

See: geode.

pot bottom

A large boulder or concretion having the rounded appearance of the bottom of an iron pot and easily detached from the roof of a coal seam. See also: camel back; kettle bottom; tortoise. CF: caldron bottom; bell. Syn: pot; potstone.


Inferior opal that does not exhibit play of color; found in association with precious opal (Australia).


a. The words potential and voltage are synonymous and mean electrical pressure. The potential of a circuit, machine, or any piece of electrical apparatus means the voltage normally existing between the conductors of such a circuit or the terminals of such a machine or apparatus. In U.S. Bureau of Mines practice: (1) any potential less than 301 V shall be deemed a low potential; (2) any potential greater than 301 V but less than 651 V shall be deemed a medium potential; and (3) any potential in excess of 651 V shall be deemed a high potential.

b. Any of several different scalar quantities, each of which involves energy as a function of position or of condition; e.g., the fluid potential of groundwater.

potential crater zone

This is the region in which, if a sufficient quantity of explosive is used, the rock will be shattered and projected outward to form a crater.

potential-determining ion

Any ion which leaves the surface of a solid immersed in aqueous liquid before equilibrium (saturation point) has been reached, while an electrical double layer is building up and zeta-potential develops.

potential difference

The difference in electric potential between two points; represents the work involved or the energy released in the transfer of a unit amount of electricity between them.

potential energy

The form of mechanical energy a body possesses by virtue of its position. If a body is being dropped from a higher to a lower position, the body is losing potential energy, but if a body is being raised, then it gains potential energy.

potential gradient

An ascending or descending value of voltage related to a linear measurement, such as a distance along the Earth surface or ground.

potential ore

Inferred reserves. See: reserves.

potentiometric surface

An imaginary surface representing the total head of ground water; defined by the level to which water will rise in a well. The water table is a particular potentiometric surface. Syn: piezometric surface; pressure surface.


a. A kettlelike or circular depression, generally deeper than wide, worn into the solid rock in a stream bed at falls and strong rapids by sand, gravel, and stones being spun around by the force of the current. Also called a kettle hole; swallow hole.

b. A kettlelike to irregular steep-walled subcircular interruption of bedding in the Merensky Reef of the Bushveld Complex, South Africa. It is filled with younger material. c. A term used in Death Valley, California, for a circular opening, about a meter in diameter, filled with brine and lined with halite crystals. d. An underground system of pitches and slopes. Applied in some cases to single pitches reaching the surface. e. A rounded, steep-sided depression resulting from downward surface solution. f. The occurrence, in the nether roof of a coal seam, of an irregularly shaped mass generally broader at its base than elsewhere and with smooth sides (slickensides). g. A circular or funnel-shaped depression in the surface caused by subsidence. h. A rounded cavity in the roof of a mine caused by a fall of rock, coal, ore, etc. i. A vertical pitch open to the surface. j. See: abyss.

pot kiln

A small limekiln.

pot lead

a. An obsolete term for graphite or black lead.

b. Graphite used on the bottoms of racing boats.


Eng. Flattened oval dogger of flaggy sandstone; so called because sometimes the upper or under layers, when split off, resemble potlids. CF: baum pot.

pot ore

Foliated galena.

pot setting

In glassmaking, the placing of a pot in a furnace for the purpose of melting metal.


a. Impure steatite or massive talc; used in prehistoric times to make cooking vessels. Also spelled pot stone.

b. See: paramoudra.


A skilled craftsperson who fabricates ceramic ware using various forming techniques.

pottern ore

A term used in early metallurgical practice for an ore that becomes vitrified by heat, like the glazing of earthenware.

potter's asthma

See: potter's consumption.

potter's bronchitis

See: potter's consumption.

potter's clay

A plastic clay free from iron and devoid of fissility; suitable for modeling or making of pottery or adapted for use on a potter's wheel. It is white after burning.

potter's consumption

An acute bronchitis often occurring among pottery employees, eventually affecting the lungs.

pottery spar

A 200-mesh feldspar produced for use by the manufacturers of chinaware, sanitary ware, ceramic tile, frits, enamel, glazes, electrical insulators, and vitrified grinding wheels.


The placing of pots, containing either potassium nitrate or sodium nitrate and sulfuric acid, in the kilns used in the manufacture of sulfuric acid from sulfurous acid obtained from the combustion of sulfur in air.

potty ore

Som. Brown iron ore, Brendon Hills. Apparently a color term, since the two varieties of ore are black and potty.

Poulter method

A seismic technique that dispenses with the need for drilling shotholes. In this air-shooting method, dynamite is exploded in arrays of simultaneous blasts with charges several feet above the ground. The principal difficulty involves the hazard of working with aboveground explosives and the damage to property or to the peace of mind of nearby inhabitants.


Wales. Underclay. Apparently a survival of the obsolete form of puncheon (punchin)--a supporting timber in a coal mine or in a building floor timber. Also spelled pounson.


a. A large, natural fissure or cavity in strata.

b. An underground reservoir of water. See also: lodge.


a. A hybrid term between the English and metric units and defined as the amount of heat required to raise 1 lb (0.454 kg) of water 1 degrees C.

b. An engineering heat unit, often called centigrade heat unit (chu). Defined as above. Approx. equal to 1.8 Btu (1.9 kJ).


An ore-mill stamp.


Unit of bending moment being the moment due to a force of 1 lb (0.454 kg) applied at a distance of 1 ft (30.48 cm).


In founding: (1) the amount of material, as melted metal, poured at a time; and (2) the act, process, or operation of pouring melted metal; such as, make a pour at noon.

poured fitting

A connecting device that is fastened to the end of a cable (wire rope) by inserting the cable end in a funnel-shaped socket, separating the wires and filling the socket with molten zinc.

pouring basin

A basin on top of a mold to receive the molten metal before it enters the sprue or downgate.

pouring gate

A channel in a mold through which to pour molten metal.

pouring pit refractory

In the steel industry, refractory used for the transfer of steel from furnace to ingot. Refractories include ladle brick, nozzles, sleeves, stopper heads, mold plugs, hot tops, and mortars used for the brickwork involved.


In glassmaking, a long iron rod for either drawing out glass or twisting it to a fine thread.


A general term for explosives including dynamite, but excluding caps.

powder barrel

A barrel made for the conveyance of gunpowder, usually holding 100 lb (45.4 kg). CF: powder keg.

powder box

A wooden box in a miner's breast or chamber, in which were kept black powder, cartridge paper, cartridge stick, squibs, lampwick, chalk, and tools. Syn: tool box.

powder carrier

See: powder monkey.

powder chest

A substantial, nonconductive portable container equipped with a lid and used temporarily at blasting sites for storage of explosives other than blasting agents. Unused explosives are returned to the magazine at the end of the shift. Syn: day box. CF: magazine.

powdered coal

Coal that has been crushed fine; may be transported by air to fire a boiler or industrial heating furnace.

powdered ore

Aust. Ore disseminated with veinstuff.

powder explosive

An explosive containing still smaller quantities of liquid products, compared with plastic and semiplastic explosives, so that the spaces between the solid particles are not filled out entirely. As the result of this, the density of the mass is 20% to 40% lower than that of plastic and semiplastic explosives.

powder factor

The quantity of explosive used per unit of rock blasted, measured in lb/yd (super 3) (kg/m (super 3) ) per ton (metric ton) of rock.

powder house

A magazine for the temporary storage of explosives. See also: magazine.

powder keg

A small metal keg for black blasting powder, usually having a capacity sufficient for 25 lb (13.5 kg) of powder. CF: powder barrel.


a. A person in charge of explosives in an operation of any nature requiring their use.

b. In bituminous coal mining and metal mining, one who handles proper storage of explosives in a powder house at a mine and issues powder, dynamite, caps, detonators, and fuses to miners as needed. At smaller mines, may deliver explosives to miners at working places. Also called powder monkey. See also: blaster.

powderman helper

See: powder monkey.

powder metal

As used in the diamond-drilling industry, the finely divided particles of iron, copper, nickel, zinc, tungsten carbide, etc., which, when mixed with a suitable binding material and subjected to processing by heat and pressure, may be used as a matrix material to form a bit crown.

powder-metal bit

Any diamond bit, mechanically set, in which finely divided metal powders are used as a matrix to hold the diamonds in place. Also called powder-pressed bit; powder-set bit; sinter bit; sintered-metal bit.

powder metallurgy

The art of producing and utilizing metal powders for the production of massive materials and shaped objects.

powder-metallurgy technique

A metallurgical technique in which metal powder is pressed into a desired shape.

powder-metal process

The process of mechanically setting diamonds in a bit in a matrix of finely divided metal powders. The metal powder is first cold pressed to compact it in a bit mold or die and then heated to allow the bonding alloy to melt and bind the powder to the diamonds and bit blank. Hot pressing or coining follows heating of the powder in some modifications of the process.

powder mine

An excavation filled with powder for the purpose of blasting rocks.

powder monkey

a. A person employed at the powder house of a coal mine whose duty is to deliver powder to the miners.

b. In some metal mines, the person who distributes powder, dynamite, and fuses to the miners at the working faces. This is a nautical term, but is frequently used in the mining industry. c. In the quarry industry, one who carries powder or other explosives to the blaster and assists by placing prepared explosive in a hole, connecting a lead wire to a blasting machine, and performing other duties as directed. Also called blaster helper; powder carrier; powderman helper. See also: powderman.

powder pattern

The array of monochromatic X-ray diffractions produced by a mineral powder. CF: crystallogram.

powder porosity

Ratio of the volume of voids between particles, plus the volume of pores, to the volume occupied by the powder, including voids and pores.


A tetragonal mineral, CaMoO (sub 4) ; forms a series with scheelite as tungsten replaces molybdenum; a minor source of molybdenum in Idaho, Michigan, Nevada, and California, and Siberia, Russia.

powellizing process

A wood treatment consisting of impregnating the wood with a saccharin solution. It hardens the wood, and renders it fireproof to some extent.


a. Any form of energy available for doing any kind of work; e.g., steam power and water power. Specif., mechanical energy, as distinguished from work done by hand.

b. Used loosely to indicate the electric current in a wire. c. Rate of doing work. The foot-pound-second (fps) unit of power is the horsepower (hp), which is a rate of working equal to 550 ft.lbf/s (745.7 W). The electrical power unit, the watt, equals 10 (super 7) cm-gram-second (cgs) units; i.e., 10 (super 7) erg/s or 1 J/s.

power arm

The part of a lever between the fulcrum and the point where force is applied.

power barrow

See: pedestrian-controlled dumper.

power control unit

One or more winches mounted on a tractor and used to manipulate parts of bulldozers, scrapers, or other machines.

power control winch

A high-speed tractor-mounted winch with one to three drums; used chiefly for operating bulldozers, scrapers, and rooters.

power dragscraper

A machine consisting of: (1) a bottomless scraper bucket; (2) a two-drum hoist; (3) two long cables that attach to the front and rear of the scraper; (4) a movable tail block; (5) a short, guyed mast located behind a ground hopper or other delivery point; and (6) two sheave blocks mounted on the mast to guide the operating cables to the hoist. The tail block is shifted manually from time to time, swinging the scraper in a wide arc until all the material within the operating radius has been taken out.

power earth auger

A mechanically operated auger for exploring and testing deposits that are not very hard. The drilling rig may be mounted on a lorry or on continuous tracks when greater depths may be reached.

powered supports

In fully mechanized coal mining, a system of pit props connected to a flexible armored conveyor by means of hydraulic rams.

power factor

a. The ratio of the mean actual power in an alternating-current circuit measured in watts to the apparent power measured in volt-amperes; equal to the cosine of the phase difference between electromotive force and current.

b. The ratio of the total watts input to the total root-mean-square volt-ampere input to a rectifier or rectifier unit. c. A clause frequently found in electric power contracts, which sets forth that if a customer permits the average power factor of the load used to fall below a specified value, a penalty charge will be made. Power factor is often defined as the ratio of actual power to apparent power and is usually expressed as a percentage.

power-factor meter

Meter that indicates the relation of the phase between the line current and the line voltage, which actually is the same as the power factor of the load.

power grizzly

Power-operated machine used mainly for removing dirt and fines from material to be crushed. There are three main types--the live-roll grizzly, the vibrating-bar grizzly, and the bar grizzly feeder. See also: static grizzly.

power-operated supports

See: self-advancing supports.

power pack

a. In general, an electrically operated hydraulic pump, placed at the gate end, to supply power to face equipment; e.g., self-advancing supports. The system forms a closed circuit with the oil returning to a reservoir containing about 212 gal (800 L) of oil. The pump can supply 2-1/2 gal (9.5 L) of oil per unit at 2,000 psi (13.8 MPa), which allows a setting load of about 9 st (8 t) per prop. See also: hydraulic power. b. A unit that converts AC or DC current to AC or DC voltages suitable for the operation of electronic equipment.

power rammer

A manually operated compacting machine, weighing about 200 lb (91 kg), raised by an intrinsic internal combustion mechanism and allowed to fall by gravity. See also: mechanical rammer.

power sequence

A sequence control system that is suitable for a group of conveyors in tandem. The trunk conveyor contactor is first closed; after a delay of from 3 to 15 s, sufficient for its motor to come up to speed, power is switched on to the contactor of the second conveyor; finally, after a similar delay, power is switched on to the third conveyor or conveyors. All power comes through the number 1 conveyor contactor so that, if this conveyor is stopped, all other conveyors in tandem stop as well. See also: sequence starting.

power shovel

An excavating and loading machine consisting of a digging bucket at the end of an arm suspended from a boom, which extends cranelike from the part of the machine that houses the powerplant. When digging, the bucket moves forward and upward so that the machine does not usually excavate below the level at which it stands. See also: shovel loader.

power-shovel mining

Power shovels are used for mining coal, iron ore, phosphate deposits, and copper ore. The shovels may be used either for mining or for stripping and removing the overburden, or for both types of work, although at some coal mines the shovels used for stripping are considerably larger than those used for other mining.

power station

An assemblage of machines and equipment, including the necessary housing, where electrical energy is produced from some other form of energy. Steam boilers are fed with coal or oil and the heat generated is used to produce high-pressure steam. The steam then passes to turbines that drive the generators and thus produce electricity.

power takeoff

A place in a transmission or engine to which a shaft can be attached so as to drive an outside mechanism.

power tongs

A mechanically powered wrench used to make up or break out a drill rod, casing, or pipe string.

power train

All moving parts connecting an engine with the point where work is accomplished.

power unit

a. Generally applied to any device used to drive or operate machinery around a mine. Specif., it is used for the motor-speed reducer combination used to drive belt and chain conveyors.

b. That part of a mining belt conveyor that consists of a power unit base, an electric motor, an electric controller, a speed reducer with a flexible coupling between motor and speed reducer, a power transmission device to power the drive pulley or pulleys, suitable covers for all moving parts and, if the power unit is of the detachable type, a device for attaching it to the conveyor.

power upon the air

In coal mine ventilation, the horsepower applied is often known as the power upon the air. This may be the power exerted by a motive column due to the natural causes, to a furnace, or it may be the power of a mechanical motor. The power upon the air is always measured in foot pounds per minute.


a. A leucitic tuff quarried near Pozzuoli, Italy, and used in the manufacture of hydraulic cement. The term is now applied more generally to a number of natural and manufactured materials, such as ash and slag, that impart specific properties to cement. Pozzolanic cements have superior strength when cured and are resistant to saline and acidic solutions. Also spelled: pozzolan; pozzuolana; pozzuolane. See also: gaize.

b. A material that is capable of reacting with lime in the presence of water at ordinary temperature to produce a cementitious compound. Natural pozzolanas are siliceous material of volcanic origin. They include trass and Santorin earth. Blast furnace slag is used to produce artificial pozzolanas.

pozzolana cement

A cement produced by grinding together portland cement clinker and a pozzolana, or by mixing together a hydrated lime and a pozzolana. Syn: Roman cement.