Appendix:Dictionary of Mining, Mineral, and Related Terms/P/3

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The negative logarithm (base 10) of the hydrogen-ion activity. It denotes the degree of acidity or of basicity of a solution. At 25 degrees C, 7 is the neutral value. Acidity increases with decreasing values below 7, and basicity increases with increasing values above 7.


See: kaliophilite. Also spelled phacelite.


A concordant intrusive in the crest of an anticline and trough of a syncline; in cross section, it has the shape of a doubly convex lens. Adj: phacolithic. See also: laccolith.


An igneous rock having the grains of its essential minerals large enough to be seen macroscopically.


Said of the texture of an igneous rock in which the individual components are distinguishable with the unaided eye, i.e., megascopically crystalline. Also, said of a rock having such texture. CF: aphanitic. Syn: macromeritic; phanerocrystalline; phenocrystalline.


See: phaneritic.


That part of geologic time represented by rocks in which the evidence of life is abundant, i.e. Cambrian and later time. CF: Cryptozoic.

phantom crystal

A crystal or mineral aggregate within which an earlier stage of crystallization or growth is outlined by dust, tiny inclusions, or bubbles; e.g., a trigonal scalenohedron of calcite coated with hematite and overgrown with a clear calcite rhombohedron in crystallographic continuity. Syn: ghost crystal.

phantom horizon

a. In seismic reflection prospecting, a line drawn on seismic sections so that it is parallel to nearby dip segments thought to indicate structural attitude. It is used where actual events are not continuous enough to be used alone.

b. Horizon on a reflection profile that is obtained by averaging the dips of the reflections within a band, thus indicating the trend of the dip, but not necessarily coinciding with an actual boundary plane.


A monoclinic mineral, CaHAsO (sub 4) .2H (sub 2) O ; white to gray; forms silky fibers; occurs in the oxidized parts of arsenical deposits. Syn: arsenic bloom.


An isometric mineral, KFe (sub 4) (AsO (sub 4) ) (sub 3) (OH) (sub 4) .6-7H (sub 2) O; crystallizes in cubes or tetrahedra with cubic cleavage; rarely massive; occurs widely as an oxidation product of arsenical ores. Syn: cube ore.


a. The sum of all those portions of a material system that are identical in chemical composition and physical state.

b. A homogeneous, physically distinct portion of matter in a heterogeneous system. c. An interval in the development of a given process; esp. a chapter in the history of the igneous activity of a region, such as the volcanic phase and major and minor intrusive phases. d. A lithologic facies, esp. on a small scale, such as a minor variety within a dominant or normal facies, or a facies of short duration or local occurrence; e.g., a marine phase or a fluviatile phase.

phase angle

An angle expressing phase or phase difference.

phase-balance relay

Relay that protects an electrical system from faults occurring in any phase of a three-phase system. Quite often a fault current will not be large enough to trip the overcurrent relay, but will operate the phase-balance mechanism.

phase control

The process of varying the point within the cycle at which anode conduction is permitted to begin.

phase converter

A machine for converting an alternating current into an alternating current of a different number of phases and the same frequency.

phase diagram

A graph designed to show the boundaries of the fields of stability of the various phases of a system. The coordinates are usually two or more of the intensive variables temperature, pressure, and composition, but are not restricted to these. Syn: equilibrium diagram.

phase disengagement

In solvent extraction or liquid-liquid extraction procedures, allowing the mixture of aqueous liquor and organic solution phases to separate for individual recovery and further treatment.

phase disengagement rate

In solvent extraction technology, the rate of disengagement of phases (aqueous and organic carrier).

phase displacement

The angle by which the amount of difference of phase between two alternating-current magnitudes is expressed.

phase equilibria

The study and determination of stable phases present under various conditions of pressure, temperature, and composition according to the Gibbs phase rule; used in the study of mineral genesis. CF: crystallogeny.

phase inversion

In the Convertol process, replacement of the film of water covering a coal particle by a film of oil.


A device for measuring the difference in phase of two alternating currents or electromotive forces.

phase rule

The statement that for any system in equilibrium, the number of degrees of freedom is two greater than the difference between the number of components and the number of phases. It may be symbolically stated as F = (C-P) + 2. See also: mineralogical phase rule.

phase shifter

A device employed to alter the phase of a wave.

phase system

Any portion of the universe that can be isolated completely and arbitrarily from the rest for consideration of the changes that may occur within it under varied conditions. In a closed system, energy may cross the system boundary, but matter may not. In an open system, both energy and matter may enter or leave as required. An equilibrium system is closed with all phases in their lowest energy states. The variance (degrees of freedom) of an equilibrium system is its number of components minus its number of phases plus two. A steady-state system is open with all phases in their lowest energy states while matter streams through it. Systems may be described by the number of their components; e.g., unary for one component, binary for two, ternary for three, etc. They are commonly defined in terms of their components; e.g., the system CaO-MgO-SiO (sub 2) -H (sub 2) O is a quaternary system.

phase transformation

The inversion of one crystalline assemblage of components from one symmetry to another; e.g., calcite to aragonite.


See: phenakite.


A trigonal mineral, Be (sub 2) SiO (sub 4) ; colorless to yellow, red, or brown; a minor gemstone sparsely found in granite pegmatites. It is sometimes confused with quartz. Not to be confused with fenaksite. Syn: phenacite.


a. A variety of muscovite having high silica.

b. A transparent or translucent stone (probably crystalline gypsum) used by the ancients for windows.


a. Applied to certain conditions under which coal was formed, namely those of open waters into which the plant debris was swept from the adjoining land.

b. Refers to vegetable matter deposited under water in contrast to that laid down on a wet substratum. CF: crypthydrous.


A term for large crystals or mineral grains floating in the matrix or groundmass of a porphyry. Syn: inset.


See: phaneritic.


A soluble, crystalline acidic compound; C (sub 6) H (sub 5) OH ; has a characteristic odor. It is present in coal tar and in wood tar. It is a powerful caustic poison and in a dilute solution, a useful disinfectant. Used chiefly in making resins and plastics, dyes, and pharmaceuticals (such as aspirin). Syn: benzenol; hydroxybenzene; carbolic acid.

phi grade scale

A logarithmic transformation of the Wentworth grade scale in which the negative logarithm to the base 2 of the particle diameter (in millimeters) is substituted for the diameter value (Krumbein, 1934); it has integers for the class limits, increasing from -5 for 32 mm to +10 for 1/1,024 mm. The scale was developed specif. as a statistical device to permit the direct application of conventional statistical practices to sedimentary data. See also: Wentworth grade scale.

Philadelphia rod

A leveling rod in which the hundredths of feet, or eighths of inches, are marked by alternate bars of color the width of the measurement.


A compact, blue, hydrated copper and iron sulfate, Fe (sub 2) Cu(SO (sub 4) ) (sub 4) .12H (sub 2) O , produced by decomposition of chalcopyrite.


A monoclinic mineral, (K,Na,Ca) (sub 1-2) (Si,Al) (sub 8) O (sub 16) .6H (sub 2) O ; zeolite group; commonly occurs in complex twinned crystals; in basalt amydules, in pelagic red clays, in palagonite tuffs, in alkaline saline lakes from silicic vitric volcanic ash, in alkaline soils, and around hot springs in Roman baths.

Phleger corer

Designed to obtain cores up to about 4 ft (1.2 m) in length, the Phleger corer is utilized where only the upper layers of the sea bottom are to be analyzed.


In coal, the outer conducting part of the central cylinder or vascular tissues. It consists primarily of sieve tubes and companion cells, phloem fibers or bark fibers, stone cells, and parenchymatous cells.


A monoclinic mineral, K (sub 2) Mg (sub 6) (Si (sub 6) Al (sub 2) O (sub 20) )(F,OH) (sub 4) ; a magnesium-rich end-member of the biotite crystal solution series; mica group; pseudohexagonal with perfect basal cleavage; occurs in crystalline limestones as a product of dedolomitization, in potassium-rich ultramafic rocks, as an alteration mineral in sulfur-rich hydrothermal assemblages, and in kimberlites. Syn: magnesium mica; amber mica; brown mica.

pH modifier

Proper functioning of a cationic or anionic flotation reagent is dependent on the close control of pH. Modifying agents used are soda ash, sodium hydroxide, sodium silicate, sodium phosphates, lime, sulfuric acid, and hydrofluoric acid.


A claylike mineral closely related to or identical with kaolinite.


The group of aluminous glauconites grading into normal (ferruginous) glauconite and occurring in sedimentary rocks. Includes skolite and bravaisite. Distinct from pholidolite of Nordenskiold. CF: illite.


The extrusive equivalent of nepheline syenite. The principal mineral is soda orthoclase or sanidine. Other major minerals are nepheline and aegirine diopside, usually with other feldspathoidal minerals such as sodalite or haueyne. Accessories include apatite and sphene. Phonolite is an important ore progenitor, as at Cripple Creek, CO. Syn: clinkstone.


A tetragonal mineral, 4[Pb (sub 2) (CO (sub 3) )Cl (sub 2) ] ; forms stubby crystals; may be massive; adamantine; sp gr, 6.13; (super ) a secondary mineral in lead deposits and from action of seawater on lead slags and artifacts; commonly associated with cerussite and anglesite. Syn: horn lead.


Phosphorite that occurs as beds of small concretions resting on clay surfaces or scattered in sands and limestone.


a. n. Any mineral containing essential tetrahedral phosphate, (PO (sub 4) ) (super 3-) , structural entities; e.g., apatite, amblygonite, or monazite.

b. A mineral commodity supplying phosphorus, usually for agricultural or chemical purposes. The source materials for phosphate are marine phosphorite and, less commonly, guano and apatite-rich igneous rocks. c. Adj., phosphatic. Pertaining to or containing phosphates or phosphoric acid; said esp. of a sedimentary rock containing phosphatic minerals, such as phosphatic limestone produced by secondary enrichment of phosphatic material, or a phosphatic shale representing mixtures of primary and secondary phosphate and clay minerals. CF: vanadate.

phosphate lands

In mining law, a leased area for phosphate lands may not exceed 2,560 acres (1,034 ha). A certain expenditure for mine development and operations is required. A royalty of not less than 2% of the gross value of the output must be paid, and an annual rental, similar to that for coal lands, is imposed.

phosphate of lime

See: apatite.

phosphate rock

Any rock that contains one or more phosphatic minerals of sufficient purity and quantity to permit its commercial use as a source of phosphatic compounds or elemental phosphorus. About 90% of the world's production is sedimentary phosphate rock, or phosphorite; the remainder is igneous rock rich in apatite. Syn: rock phosphate.

phosphatic nodule

Black to brown, rounded mass, variable in size from a few millimeters to 30 or more centimeters. Usually consists of coprolites, corals, shells, and bones, more or less enveloped in crusts of collophane. Found in many horizons of marine origin. Also covering the ocean floors at many locations around the world.


A compound that is a combination of phosphorus with a metal; e.g., schreibersite, (Fe,Ni) (sub 3) P .


See: pseudomalachite.


A monoclinic mineral, Zn (sub 2) (Fe,Mn)(PO (sub 4) ) (sub 2) .4H (sub 2) O ; forms tabular crystals with perfect cleavage; vitreous; colorless to pale blue-green; a secondary mineral from pegmatites; possibly in some oxidized base-metal deposits.


Any material that has been prepared artificially and has the property of luminescence, regardless of whether it exhibits phosphorescence.


a. To combine or to impregnate with phosphorus; as phosphorated oil. Syn: phosphorize.

b. To make phosphorescent.

phosphor bronze

An elastic, hard and tough alloy, composed of 80% to 95% copper, 5% to 15% tin, with phosphorus up to 2.5%.


a. Luminescence in which the stimulated substance continues to emit light after the external stimulus has ceased; also, the light so produced. The duration of the emission is temperature-dependent, and has a characteristic rate of decay. CF: fluorescence; luminescence.

b. A misnomer for the property of emitting light without sensible heat; luminescence. Although light is produced by a biochemical reaction involving phosphorus, bioluminescence is the preferred term.

phosphoric acid

A clear, colorless, sparkling liquid or a transparent orthorhombic crystal; H (sub 3) PO (sub 4) (orthophosphoric acid), depending on the concentration and the temperature. At ordinary atmospheric temperature (20 degrees C), the 50% and 75% acids are mobile liquids, the 85% acid is syrupy, and the 100% acid is in crystals; specific gravity, 1.834 (at 18 degrees C); melting point, 42.35 degrees C; boiling point, 260 degrees C; soluble in water and in alcohol; and very corrosive to ferrous metals and alloys.


A sedimentary rock with a high enough content of phosphate minerals to be of economic interest. Most commonly it is a bedded primary or reworked secondary marine rock composed of microcrystalline carbonate fluorapatite in the form of laminae; pellets; oolites; nodules; skeletal, shell, and bone fragments; and guano. Aluminum and iron phosphate minerals (wavellite, millisite) are usually of secondary formation. See also: brown rock; bone phosphate; pebble phosphate.


See: phosphorate.

phosphorized copper

A general term applied to copper deoxidized with phosphorus. The most commonly used deoxidized copper.


See: pseudomalachite.


A substance that promotes phosphorescence in a mineral or other compound.


A nonmetallic element of the nitrogen group. Symbol, P. Never found free in nature, but is widely distributed in combination with minerals. An important source is phosphate rock, which contains the mineral apatite. Ignites spontaneously, and is very poisonous; must be kept under water. Used in safety matches, pyrotechnics, pesticides, incendiary shells, smoke bombs, tracer bullets, and fertilizers. Syn: amorphous phosphorus.

phosphorus copper

Copper that contains about 15% phosphorus. Used chiefly as a deoxidizer for molten metals.

phosphorus steel

Steel in which phosphorus is the principal hardening element.


A monoclinic mineral, Fe (super 3+) PO (sub 4) .2H (sub 2) O ; iron may be replaced by aluminum; dimorphous with strengite; isomorphous with metavariscite; forms tabular crystals or reniform crusts; vitreous; occurs in a wide variety of settings where iron and phosphate are in proximity. Formerly called metastrengite, clinostrengite.


An orthorhombic mineral, Ca(UO (sub 2) ) (sub 3) (PO (sub 4) ) (sub 2) (OH) (sub 2) .6H (sub 2) O ; radioactive; deep yellow; earthy or as crusts or tiny scales; associated with autunite and other secondary uranium minerals, esp. in pegmatites.


Described as altered rhodonite; carbonated rhodonite.


A property of certain transparent substances that enables the presence of strain to be detected by examination in polarized light. If models of complicated engineering structures are made of such a substance, the stress distribution in the structure may be resolved. See also: model analysis; isochromatic lines; stress analysis.

photoelectric cell

Broadly, any device in which the incidence of light causes a change in the electrical state.


The photography of images produced on a fluorescent screen by X-rays. Varieties include photoradiography, photoroentgenography, miniature radiography.


The identification, recording, and study of geologic features and structures by means of photography; specif. the geologic interpretation of aerial and space photographs and images and the presentation of the information so obtained. It includes the interpretation of second-generation photographs obtained by photographing images recorded on television-type tubes (the images recording wavelengths outside the visible spectrum).


Study of earth forms as revealed by aerial photographs.


The art and science of obtaining reliable measurements from photographic images. Methods utilize horizontal, vertical, and oblique views, with or without the aid of the stereoscopic principle and with or without computer-based image processing and analysis. See also: infrared photography.

photographic borehole survey

A method of checking verticality and/or orientation of a long borehole. A compact camera inserted at a known depth takes a photograph of a magnetic needle and/or a clinometer. Instruments have been developed by Oehman, Owen, and Wright.

photographic interpretation

See: photointerpretation.

photographic-paper recorder

A small device for registering photographically the passage of flame. This must not be confused with the photographing of the flame on the manometer record.


The extraction of information from aerial photographs and images for a particular purpose, such as mapping the geologic features of an area. Syn: photographic interpretation.


Autotrophic microorganism that derives energy to do metabolic work by converting radiant energy into chemical energy and assimilates carbon as CO (sub 2) , HCO (sub 3) (super -) , or CO (sub 3) (super 2-) (photosynthesis). See also: autotroph.


See: macrograph.

photomagnetic borehole surveying

A method of borehole surveying, consisting essentially of a timing clock, batteries and light bulb, a floating light-transparent compass, an inclination unit, and a photographic film for recording both the position of the compass and the crosshairs of the inclinometer. The instrument is enclosed in a nonmagnetic casing. See also: multishot gyroscopic instrument. Syn: single shot.

photometric method

A dust-sampling method in which samples of dust are collected on filter paper and then placed in a photometer. The instrument shows the intensity of a beam of light after it has passed through the paper, and the fall in intensity is a direct measure of the dust concentration. With dark dust, such as in coal mines, a rough indication of the dustiness may be obtained by comparison of the depth of tone with a graded series of samples that have been calibrated against some other instrument. There are two methods of collecting samples for photometric estimation: (1) by passing the air through a filter paper, as for gravimetric estimation; or (2) by impingement, as in the konimeter.


A photographic enlargement of a microscopic image such as a petrologic thin section; a type of micrograph. Less-preferred syn: microphotograph.


A sensitive detector of light in which the initial electron current, derived from photoelectric emission, is amplified by successive stages of secondary electron emission.


A discrete quantity of electromagnetic energy. Photons have momentum but no mass or electrical charge.


Term applied to minerals (e.g., chlorargyrite, utenbogaardite) that are visibly injured by light.

photostat printing

A method of reproducing a drawing on opaque paper by printing from a photographic negative, which enables the original drawing to be enlarged or reduced.


A ground-surveying instrument used in terrestrial photogrammetry, combining the functions of a theodolite and a camera mounted on the same tripod.


The reversible change in color of a substance produced by the formation of an isomeric modification when exposed to radiant energy (such as light).

phragmites peat

Peat composed of reed grass and other grasses.


Pertaining to ground water.

phreatic explosion

A volcanic eruption or explosion of steam, mud, or other material that is not incandescent; it is caused by the heating and consequent expansion of ground water due to an underlying igneous heat source.

phreatic gas

Any of the vapors and gases of atmospheric or oceanic origin which, coming into contact with ascending magma, may provide the motive force for volcanic eruptions.

phreatic line

See: line of seepage.

phreatic surface

See: water table.

phreatic water

A term that originally was applied only to water that occurs in the upper part of the zone of saturation under water-table conditions (syn. of unconfined ground water, or well water), but has come to be applied to all water in the zone of saturation, thus making it an exact syn. of ground water.

phreatic zone

See: zone of saturation.

pH regulator

Substance used in flotation processes to control the hydrogen-ion concentration. See also: pH.


Siliceous shale. The term is used esp. by European geologists. Also spelled phtanite.


Miner's occupational disease, a form of lung consumption associated with or aggravated by work in dusty surroundings, such as badly ventilated underground workings. See also: pneumoconiosis.

phyllic alteration

Hydrothermal alteration typically resulting from removal of sodium, calcium, and magnesium from calc-alkalic rocks, with pervasive replacement of silicates, muting the original rock texture. It is a common style of alteration in porphyry base-metal systems around a central zone of potassic alteration. See also: propylitization.


a. A metamorphic rock, intermediate in grade between slate and mica schist. Minute crystals of sericite and chlorite impart a silky sheen to the surfaces of cleavage (or schistosity). Phyllites commonly exhibit corrugated cleavage surfaces. CF: illite; phyllonite.

b. A general term for minerals with a layered crystal structure. c. A general term used by some French authors for the scaly minerals, such as micas, chlorites, clays, and vermiculites.


See: phyllonite.

phyllitic cleavage

Rock cleavage in which flakes are produced that are barely visible to the unaided eye. It is coarser than slaty cleavage and finer than schistose cleavage.


A rock that macroscopically resembles phyllite but that is formed by mechanical degradation (mylonization) of initially coarser rocks (e.g., graywacke, granite, or gneiss). Silky films of recrystallized mica or chlorite, smeared out along schistosity surfaces, and formation by dislocation metamorphism are characteristic. Syn: phyllite-mylonite. See also: mylonite gneiss. CF: phyllite.


The processes of mylonitization and recrystallization to produce a phyllonite.


Crystalline hydrocarbon similar to fichtelite and extracted along with fichtelite from fossil pine wood.


Vitrain in which the plant remains are discernible under a microscope.


A suffix used in naming rocks that are porphyritic, such as vitrophyre, orthophyre, or granophyre.

physical depletion

The exhaustion of a mine or a petroleum reservoir by extracting the minerals.

physical geology

A broad division of geology that concerns itself with the processes and forces involved in the inorganic evolution of the Earth and its morphology, and with its constituent minerals, rocks, magmas, and core materials. CF: historical geology. See also: geology.

physical mineralogy

That branch of mineralogy which treats of the physical properties of minerals. CF: chemical mineralogy.

physical oceanography

That marine science which treats of the Earth's water mass as a fluid and studies its physical properties of motion, density, temperature, etc.

physical shock

A state of collapse that interferes with the normal heart action, respiration, and circulation. This condition is probably due to derangement or lack of proper balance within the sympathetic nervous system and may be caused by any number of things, such as serious injury, loss of blood, severe burns, fright, and many others. It is important to look for shock when rendering first aid since it may cause death even when the injury is less serious.


The science, or group of sciences, that treats of the phenomena associated with matter in general, esp. in its relations to energy, and of the laws governing these phenomena, excluding the special laws peculiar to living matter (biology) or to special kinds of matter (chemistry). Physics treats of the constitution and properties of matter, mechanics, acoustics, heat, optics, electricity, and magnetism. More generally, it includes all the physical sciences.

physiographic province

A region of which all parts are similar in geologic structure and which has consequently had a unified geomorphic history; a region whose pattern of relief features or landforms differs significantly from that of adjacent regions.


The term was introduced by G. H. Cady in 1942, to designate plant forms or fossils in coal as distinguished from the material of which the fossils may be composed. Phyterals are identified in general botanical terms that are usually morphological, such as spore coat, sporangium, cuticle, resin, wax, wood substance, bark, etc. The initial composition of the phyterals differed; these or other differences produced during diagenesis may or may not be perpetuated by and during carbonification (coalification). Phyterals are recognized with increasing difficulty in high rank coals. In contrast to macerals which represent a purely petrographical concept, the concept phyteral demands strict correlation with certain organs of the initial plant material.

phytogenous rock

Rock formed from plant remains.


A rock formed by plant activity or composed chiefly of plant remains. The term was applied by Grabau to a large group including coal, peat, lignites, some types of reef limestones, and oolites.


The plant life division of plankton, including diatoms and algae. Unattached plants that are at the mercy of the currents.

piano wire screen

A screen formed by piano wires stretched tightly, lengthwise, on a frame 2 to 3 ft (0.61 to 0.91 m) wide and 4 to 8 ft (1.2 to 2.4 m) high. The screen is set up at an angle of about 45 degrees and crushed material is fed to it from above. The mesh size varies from about 4 to 16. Because there are no cross wires, and because the taut wires can vibrate, there is less tendency for blinding, but some elongated particles inevitably pass the screen.


A peak or sharply pointed hill or mountain; commonly a volcanic rock. The term is used in desert regions of the Southwestern United States.


a. Steel cutting point used on a coal-cutter chain. See also: coal-cutter pick.

b. A miner's steel or iron digging tool with sharp points at each end. It weighs from 3 to 6 lb (1.4 to 1.7 kg) and has a wood handle, fitted to the center or head, from 2 to 3 ft (0.6 to 0.9 m) in length. Syn: miner's pick. c. To dress the sides of a shaft or other excavation. d. To remove shale, dirt, etc., from coal. e. To select good ore out of a heap. f. In seismic prospecting, any selected event on a seismic record.

pick-a-back conveyor

A short conveyor which takes the coal from, and advances with, a face power loader or continuous miner. It delivers the coal onto a gate conveyor over which it runs on a bogey. See also: long piggyback conveyor.

pick-and-shovel miner

See: pick miner.

Pickard core barrel

A double-tube core barrel in X-group sizes. The distinguishing feature of the Pickard barrel is that when blocked, the inner barrel slides upward into the head, closing the water ports and stopping the flow of the circulating liquid; no additional drilling can be done without irreparably damaging the bit until the barrel is pulled and the blocked inner tube is cleared.

pick boy

In bituminous coal mining, a person who carries sharpened picks or bits for coal-cutting machines to the machine operator in underground working places. Also called pick carrier.

pick breaker

A breaker developed as the mechanical equivalent of the miner's pick. In the modern type, the picks are mounted on alternating arms, the primary and secondary picks being at different spacings so that breaking is performed in two stages. The breaker and plate belt are usually supplied as a standard unit driven from a common motor.

pick carrier

See: pick boy.


a. An employee who picks or discards slate and other foreign matter from coal in an anthracite breaker or at a picking table, or one who removes high-grade ore, iron, or scrap wood from ore as it passes on a conveyor belt to crushers.

b. A mechanical arrangement for removing slate from coal. c. A miner's needle, used for picking out the tamping of a charge that has failed to explode. Syn: piercer.


A monoclinic mineral, MgAl (sub 2) (SO (sub 4) ) (sub 4) .22H (sub 2) O ; hallotrichite group; forms acicular crystals and tufts; astringent taste; a product of surficial acid sulfate attack on aluminous rocks in mines and arid regions. Syn: magnesia alum.


a. A sighting hub. See also: backsight hub; foresight hub.

b. A short ranging rod about 6 ft (1.8 m) long. An iron rod, pointed at one end, and usually painted alternately red and white at 1-foot (30.5-cm) intervals; used by surveyors as a line of sight. See also: range pole.


a. Operation performed between mine and mill in which waste rock, wood, detritus, steel (tramp iron), or any specially separated mineral is removed from the run-of-mine ore material by hand sorting. Usually done during transit of material on belt conveyors, preferably after very large lumps and smalls have been screened off and the ore to be picked has been sufficiently washed to display a true surface. Also done on a picking table, a rotating circular disc around which hand sorters stand or sit to remove part of the ore fed radially from a central point. Picking can also be mechanized.

b. The falling of particles from a mine roof about to collapse. c. Extracting over a prolonged period an undue proportion of the richest ore from a mine, thus lowering the average grade of the remaining ore reserves; "picking the eyes out" of a mine. d. Rough sorting of ore.

picking belt

A continuous conveyor (e.g., in the form of a rubber belt or of a steel apron, steelplate, or link construction) on which raw coal or ore is spread so that selected ingredients may be removed manually. Syn: picking table; picking chute; picking conveyor.

picking chute

A chute along which workers are stationed to pick slate from coal. See also: picking belt.

picking conveyor

See: picking belt.

picking out eyes

Mining in which only the high-grade spots are taken out.

picking table

A flat, or slightly inclined, platform on which the coal or ore is run to be picked free from slate or gangue. See also: picking belt; picking conveyor.

pick lacing

The pattern to which the picks are set in a cutter chain. In this respect, it may be a balanced or an unbalanced cutter chain. Pick lacing is important as it has a bearing on the stability of the machine, on dust formation, and even on dangerous sparking.


a. An acid dip used to remove oxides or other compounds from the surface of a metal by chemical action.

b. To use such an acid dip.


The process of removing scale or oxide from metal objects by immersion in an acid bath to obtain a chemically clean surface prior to galvanizing or painting.

pick machine

Coal-cutting machine which acts percussively, and cuts with a large chisel fixed at the end of a piston reciprocated by compressed air in much the same way as a rock drill is operated.

pick mine

A mine in which coal is cut with picks.

pick miner

In anthracite and bituminous coal mining, a person who: (1) uses hand tools to extract coal in underground workings; (2) cuts out a channel under the bottom of the working face of coal (undercutting) with a pick, working several feet back into the seam; (3) breaks down a coalface with a pick; (4) bores holes with an augerlike drill for blasting, and inserts and sets off explosives in holes to break down coal; (5) shovels coal into cars and pushes them to a haulageway. Also called hand cutter; hand miner; hand pick miner; pick-and-shovel miner.

pick money

An earlier practice whereby miners paid a blacksmith for sharpening their picks.

pickrose hoist

A small haulage engine used for pulling light loads over short distances; used at junctions, loading points, and haulage transfer points. See also: winch; spotting hoist.

pick tongs

Tongs for handling hot metal.


a. Syn. for lift, as applied to hoisting drill rods from a borehole.

b. An angular crosscut, through which coal is hauled from one entry to another. See also: shoo-fly. c. See: geophone; detector. d. Transfer of metal from tools to a part, or from a part to tools, during a forming operation. e. In Alaska, a gold nugget picked up during mining operations prior to sluicing.

pickup test

A laboratory procedure used in investigating the floatability of minerals. A few grains, sized between 60 and 120 mesh, are placed, after suitable surface cleansing, under water in an observation cell which is controlled for pH, reagent concentration, temperature, and conditioning time. An air bubble is pressed down on the particles and then raised; the degree and tenacity with which they cling to it are observed.


Cutting coal with a pick, as in driving headings.

picky poke bar

A steel bar, usually of 7/8-in (2.22-cm) stock and about 4 ft (1.2 m) long, with each end sharpened, bent out at an angle of 45 degrees , the bends being 3 to 6 in (7.6 to 15.2 cm) from each end.


A former name for chromian spinel, (Mg,Fe)(Al,Cr) (sub 2) O (sub 4) .


An etching reagent consisting of a 2% to 5% solution of picric acid in ethyl alcohol. It may be used for plain carbon and low-alloy steels.

picric acid

A yellow crystalline compound, C (sub 6) H (sub 3) N (sub 3) O (sub 7) , obtained variously, such as by the action of nitric acid on phenol. It is used in dyeing and is an ingredient in certain explosives. Also called carbazotic acid; chrysolepic acid; trinitrophenic acid.

picrite basalt

Olivine-rich basalt, as formed by the settling of olivine in thick flows and sills. Commonly contains 50% or more olivine.


Magnesium chromite, MgCr (sub 2) O (sub 4) ; melting point, 2,250 degrees C; sp gr, 4.41. This spinel can be synthesized by heating a mixture of the two oxides at 1,600 degrees C; it is formed (usually with other spinels in solid solution) in fired chrome-magnesite refractories. Picrochromite is highly refractory but when heated at 2,000 degrees C, the Cr (sub 2) O (sub 3) slowly volatilizes. See also: magnesiochromite.


An asbestiform antigorite serpentine.


a. A monoclinic mineral, K (sub 2) Mg(SO (sub 4) ) (sub 2) .6H (sub 2) O ; forms highly soluble masses or crusts around fumaroles; also a rare, advanced desiccation constituent of marine evaporites. Formerly called schoenite.

b. A mineral group including boussingaultite, cyanochroite, mohrite, nickel-boussingaultite, and picromerite.


A screen to shelter workers from falling water.

Pidgeon process

A process for the production of magnesium by the reduction of magnesium oxide with ferrosilicon.


A local term for an intermediate pack without supporting walls.

piecemeal stoping

A process by which magma eats into its roof by engulfing relatively small isolated blocks, which presumably sink to depth where they are assimilated. See also: magmatic stoping.

piece weight

See: effective piece weight.


The performance of underground work on the basis of an agreement between a miner and the mine manager. Payment may be made by the yard of advance of a heading or tunnel or per ton or cubic yard of coal or ore removed. In ripping work, payment may be made by the yard advance of excavation to a specified width and height; strip packing may be built at a certain sum per yard advance or cubic yard of filling. See also: contract work; yardage.


Adj. Lying or formed at the base of a mountain or mountain range; e.g., a piedmont terrace or a piedmont pediment.---n. An area, plain, slope, glacier, or other feature at the base of a mountain; e.g., a foothill or a bajada. In the United States, the Piedmont is a plateau extending from New Jersey to Alabama and lying east of the Appalachian Mountains. Etymol: from Piemonte, a region of NW Italy at the foot of the Alps.

piedmont alluvial plain

See: bajada.


See: piemontite.

piedmont plain

See: bajada.

piedmont scarp

A small fault scarp at the foot of a mountain range and essentially parallel to the range.


An iron wedge for piercing stone.


A monoclinic mineral, Ca (sub 2) (Al,Mn,Fe) (sub 3) (OH)O(Si (sub 2) O (sub 7) )(SiO (sub 4) ) ; epidote group; less common than epidote; occurs in a variety of environments: low-grade regional metamorphic rocks, manganese deposits, and some intermediate to silicic volcanic rocks, perhaps due to metasomatism. Syn: manganepidote; piedmontite. CF: withamite.


A rectangular or sometimes circular form of column, constructed usually of concrete, hard brickwork, or masonry, and designed to support heavy concentrated loads from arches or a bridge superstructure.

pier cap

The upper or bearing part of a bridge pier; usually made of concrete or hard stone; designed to distribute concentrated loads evenly over the area of the pier.


Salt plug that rises and penetrates rock formations to shallow depths.

piercement dome

See: diapir.

piercement fold

See: diapir.


A blasting needle. See also: picker.


A prospecting method used in soft soil free from stones, in which small drivepipes are used to secure samples of underlying material or to determine the thickness of the soil.

pier dam

Dam or jetty to influence current. CF: weir. Syn: wing dam.

pietra della raja

It. A fine-grained Permian sandstone suitable for sawing and finishing.


Crystallization of a magma under pressure, such as pressure associated with orogeny.

piezoelectric axis

One of the directions in a crystal in which either tension or compression will cause the crystal to develop piezoelectric charges.

piezoelectric detector

A type of detector that depends upon the piezoelectric effect by which an electric charge is produced on the faces of a properly cut crystal of certain materials, particularly quartz and Rochelle salt, when the crystal is strained. The detector is constructed from a pile of such crystals with intervening metal foil to collect the charge. An inertia mass is mounted on the top of the crystal stack that is included in an electronic circuit.


The property exhibited by some asymmetrical crystalline materials which when subjected to strain in suitable directions develop electric polarization proportional to the strain. Inverse piezoelectricity is the effect in which mechanical strain is produced in certain asymmetrical crystalline materials when subjected to an external electric field; the strain is proportional to the electric field. Quartz is an industrially important example.


An instrument for measuring pressure head; usually consisting of a small pipe tapped into the side of a closed or open conduit and flush with the inside; connected with a pressure gage, mercury, water column, or other device for indicating head. See also: manometer.

piezometric surface

See: potentiometric surface.


a. A crude casting of metal convenient for storage, transportation, or melting; esp. one of standard size and shape for marketing run directly from the smelting furnace. CF: ingot.

b. A mold or channel in a pig bed. c. A heavily shielded container (usually lead) used to ship or to store radioactive materials. d. An air manifold having a number of pipes which distribute compressed air coming through a single large line.

pig and ore process

Modification of the open-hearth process of steel manufacture with pig iron and iron ore as the charge.

pig and scrap process

Modification of the open-hearth process of steel manufacture with pig iron and steel as the charge.

pig bed

A series of molds for iron pigs, made in a bed of sand. Connected to each other and to the taphole of the blast furnace by channels, along which the molten metal runs.

pig caster

Person who pours molten metal into hand ladles, and from ladles into molds to form ingots.


a. A room driven directly into a coal seam from the edge of a strip pit.

b. Any small poorly equipped coal mine. c. A hole in the shaft house floor through which the bucket or skip is raised or lowered. d. An opening left at the meeting of two sections of arch work, permitting the workers to close the arch and to come out. The pigeonhole itself is closed from below.

pigeonhole checker

An arrangement of checkerbrick such that each course of brick is laid in spaced parallel rows with the brick end to end; each alternate course above and below has its parallel rows at right angles to the intervening course.


A monoclinic mineral, (Mg,Fe,Ca)(Mg,Fe)Si (sub 2) O (sub 6) ; pyroxene group; crystallographically distinct from augite; occurs only in quickly chilled lavas. CF: augite.

pig foot

a. An iron clamp shaped like a pig's foot used to attach the jack to the feed chain of a continuous electric coal cutter.

b. A pipe jack with a pig foot at one end.

Piggot corer

A device for sampling bottom sediments. A core barrel is driven into unconsolidated material by an explosive charge.

piggyback conveyor

See: long piggyback conveyor.

pig handler

A laborer who removes metal pigs from molds manually and stamps heat numbers on pigs with hammer and punch.

pig lead

Commercial lead in large oblong masses or pigs.

pigment mineral

A mineral having economic value as a coloring agent. The most important are the red and yellow ochers and brown sienna, which consists of iron oxides with some impurities, and the brown umbers in which manganese oxide is also present. When the iron-oxide content is high the term oxide is used in preference to ocher.

pig metal

Metal, such as brass or copper, in its first rough casting.


A salt of alumina and organic acid, 4Al (sub 2) O (sub 3) .C (sub 12) H (sub 10) O (sub 8) .27H (sub 2) O ; formed on the surface of granite under the influence of wet vegetation.


A person delegated to the duty of punching or knocking pig iron out of chills or molds at a blast-furnace or pig-casting machine.


Timber support used in stopes to hold up the roof, consisting of a square frame of chocked round timbers and filled with waste rock. See also: cog.

pigsty timbering

Hollow pillars built up of logs laid crosswise for supporting heavy weights. See also: cribbing.

pig tailer

A laborer who helps a pusher to push loaded mine cars over long distances and up inclines where mechanical or mule haulage is not used. Also called helper-up.


A term used in England for any summit or top of a mountain or hill, esp. one that is peaked or pointed. Also, a mountain or hill having a peaked summit.

Pike process

A method for the direct production of steel by passing reducing gases over iron oxide ore, carburizing the reduced ore, and alloying it in an electric furnace. Thus, a reducing gas, heated to 900 degrees C is passed over iron oxide ore to produce metallic iron and spent gas. The carburized, partially reduced metal is melted, reduced, and alloyed in the electric furnace.


See: cobbing.


An aluminous variety of chrysocolla.


a. A timber, steel, or reinforced concrete plate or post that is driven into the ground to carry a vertical load (bearing pile) or a horizontal load from earth or water pressure (sheet pile).

b. A spiked or sharped-edged plank, beam, or even pipe or girder that is forced forward or downward (sinking) into running ground with a view to support. c. A stack of ore or stones. d. A prop of timber. e. Long thick laths, etc., answering in shafts in loose or quick ground, the same purpose as spills in levels, piles being driven vertically.

pile dam

A dam made by driving piles and filling the interstices with stones. The surfaces are usually protected with planking.

pile drawer

See: pile extractor.

pile driver

a. A machine for driving down piles; usually consisting of a high frame with appliances for raising and dropping a pile hammer or for supporting and guiding a steam or air hammer. Also called pile engine.

b. An operator of a pile driver.

pile extractor

A sheet piling extractor that works on the same principle as the piledriving hammer, except that the force of the blow is upward rather than down.

pile group

A number of piles driven or cast in situ, will sustain a much heavier load than a single pile can carry, esp. when connected by a pile cap.


This may be a drophammer, a steam hammer, or a diesel hammer of which the last two are completely automatic. Steam hammers are also able to operate on compressed air. See also: jetting.

pile head

The top of a precast concrete pile, protected during driving by packing under a pile helmet and sometimes by a timber dolly. The top of a timber pile is protected by a driving band.

pile helmet

A cast-steel cap covering and protecting the head of a concrete pile during driving. See also: drophammer.

pile sinking

A method of sinking a circular or rectangular shaft through 20 to 30 ft (6.1 to 9.1 m) of sand or mud at the surface. It cannot be used for greater depths as each ring of piles reduces the inside dimensions of the shaft. See also: pile; piling.


A structure or group of piles. See also: cofferdam.


A loosely rolled cylinder of burlap and 1/4-in-mesh (0.6-cm-mesh) hardware cloth pushed down into a borehole ahead of a string of drill rods to the point where a large crevice or small cavity has been encountered. At this point the cylinder tends to unroll partially, forming a mat that acts as a barrier against which other hole-plugging agents may collect and help seal off the opening.


a. A column of coal or ore left to support the overlying strata or hanging wall in a mine, generally resulting in a "room and pillar" array. Pillars are normally left permanently to support the surface or to keep old workings water tight. Coal pillars, such as those in pillar-and-stall mining, are extracted at a later period. Syn: stump. See also: barrier pillar; shaft pillar.

b. A block of ore entirely surrounded by stoping, left intentionally for purposes for ground control or on account of low value. c. A column of rock remaining after solution of the surrounding rock. See also: hoodoo.


A system of coal mining in which the working places are rectangular rooms usually five or ten times as long as they are broad, opened on the upper side of the gangway. The breasts usually from 5 to 12 yd (4.6 to 11.0 m) wide, vary with the character of the roof. The rooms or breasts are separated by pillars of solid coal (broken by small cross headings driven for ventilation) from 5 to 10 yd (4.6 to 9.1 m) or 12 yd (11 m) wide. The pillar is really a solid wall of coal separating the working places. When the object is to obtain all the coal that can be recovered as quickly as possible, the pillars are left thin; but where this plan is likely to induce a crush or squeeze that may seriously injure the mine, larger pillars are left and after the mine has been worked out, the pillars are "robbed" by mining from them until the roof comes down and prevents further working. In the steeply inclined seams of the anthracite regions the pillar-and-breast system is employed by working the bed in "lifts". Also called pillar-and-stall; post-and-stall; bord-and-pillar. Syn: board-and-pillar; board-and-wall.


A pillar method of working often adopted in extracting a proportion of thick deposits of salt or gypsum. The method may be adopted where the value of the mineral in the pillars is less than the cost of setting artificial supports.


A system of mining whereby solid blocks of coal are left on either side of miner's working places to support the roof until first-mining has been completed, when the pillar coal is then recovered. See also: room-and-pillar.


a. A system of working coal and other minerals where the first stage of excavation is accomplished with the roof sustained by coal or ore. See also: pillar-and-breast; post-and-stall.

b. One of the earliest methods of working coal seams in Great Britain. It is employed in thick seams and where valuable surface buildings require protection from damage by subsidence. A number of narrow roadways are driven in the coal seam to a predetermined boundary. There are two sets of roadways, driven at right angles to each other, and thus the seam is divided into a large number of square or rectangular pillars. These pillars are extracted at a later period. The driving of the narrow roadways is termed working the whole while pillar working is known as working the broken. The width of the roadways and their distance apart are governed by the thickness and nature of the coal seam and the type of roof and floor. The main headings are driven forward and connected at intervals by crosscuts or stentons for ventilation and as a second exit. The bords are driven off the main headings at fixed distances apart, and are connected at intervals by walls. The width of the main headings, crosscuts, and bords varies from 3 to 5 yd (2.7 to 4.6 m). The bords are driven from 15 to 60 yd (13.7 to 54.9 m) apart. The walls are about 2 to 3 yd (1.8 to 2.7 m) wide and driven at similar or greater intervals according to the size of pillars to be formed. Modern pillar-and-stall mining is highly mechanized. See also: crosscut; mechanized heading development; stenton. Also called bord-and-pillar.

pillar boss

In bituminous coal mining, a person who supervises the work of robbers in removing pillars of coal that were left to support the roof of working places during mining operations. Syn: rib boss.

pillar burst

Failure of remnants, promontories, as well as pillars, by crushing.

pillar caving

Removal of ore from a series of stopes or rooms, leaving pillars between. Eventually the pillars are forced or allowed to cave under the weight of the roof.

pillar coal

Coal secured in pillar robbing.

pillar drive

A wide irregular drift or entry, in firm dry ground, in which the roof is supported by pillars of natural earth or by artificial pillars of stone, without using timber.

pillar extraction

The recovery or working away of the pillars of coal that were left during the first operation of working in the pillar-and-stall method. Also called pillar mining. See also: jenkin; jud; pillar robbing; pillar extraction.

pillaring back

The operation of extracting coal pillars, on the retreating system, in a pillar method of working.

pillar line

a. The line along which pillars are being mined.

b. Air currents which have definitely coursed through an inaccessible abandoned panel or area or which have ventilated a pillar line or a pillared area, regardless of the methane content or absence of methane in such air.

pillar man

A person who builds stone packs in mine workings. See also: pack builder.

pillar methods of working

Methods of working coal seams, which have been given different names in different coalfields, such as stoop-and-room in Scotland; bord-and-pillar in Durham, England; and single and double stalls in South Wales. There are many modifications of pillar mining, but in general, there are two stages: (1) the driving of narrow roadways and thus forming a number of coal pillars, and (2) the extraction of the pillars--often on the retreating system. Pillar methods of mining are widely used in the United States, while the longwall method is favored in Great Britain. Pillar methods also are used for working stratified deposits of ironstone, rock salt, slate, and other layered minerals.

pillar mining system

Any of several systems, including the room-and-pillar system, the block system, and the bord-and-pillar system.

pillar recovery

Mining of pillars during retreat mining to increase the overall recovery of the reserve.

pillar road

a. Roadway formed in coal pillars.

b. Working road or incline in pillars having a range of longwall faces on either side.

pillar robber

See: robber.

pillar robbing

a. The systematic removal of the coal pillars or ore between rooms or chambers to regulate the subsidence of the roof. Also called pillar drawing.

b. The removal of ore pillars in sublevel stoping or slicing. See also: sublevel stoping. c. Formerly, in pillar-and-stall mining, the coal pillars left were too small, and miners were satisfied to gain some coal by robbing the pillars, usually from middle portions, the remaining coal being too dangerous to extract.

pillar robbing and hand filling

See: sublevel stoping.

pillar split

An opening or crosscut driven through a pillar in the course of extraction.

pillar strength

The formula for pillar strength can be expressed as follows: S = C (L/T) (super 1/2) where the coefficient, C, is directly dependent upon friction, L is the least pillar width, and T is the thickness.

pillar working

Working coal in much the same manner as with the pillar-and-stall system.


A rock texture characterized by piles of lobate, pillow-shaped masses; individual pillows range up to several meters across; typical of basalt that has erupted under an appreciable depth of water.

pillow block

A metal-cased rubber block that allows limited motion to a support or thrust member.

pillow lava

A general term for lava that exhibits pillow structure, mostly basalts and andesites that erupted and flowed under water. The ocean floor sodium-rich basalts known as spilites are commonly pillowed.

pillow structure

A structure, observed in certain extrusive igneous rocks, that is characterized by discontinuous pillow-shaped masses ranging in size from a few centimeters to a meter or more in greatest dimension (commonly between 30 cm and 60 cm). The pillows are close-fitting, the concavities of one matching the convexities of another. The spaces between the pillows are few and are filled either with material of the same composition as the pillows, with clastic sediments, or with scoriaceous material. Grain sizes within the pillows tend to decrease toward the exterior. Pillow structures are considered to be the result of subaqueous extrusion, as evidenced by their association with sedimentary deposits, usually of deep-sea origin. See also: pillow lava; mammillary structure.


a. A cylindrical steel bar extending through and about 8 in (20 cm) beyond the face of a reaming bit. It acts as a guide that follows the original unreamed part of the borehole and hence forces the reaming bit to follow and be concentric with the smaller-diameter, unreamed portion of the original borehole. Syn: reaming pilot. See also: plain pilot. b. A cylindrical diamond-set plug, of somewhat smaller diameter than the bit proper, set in the center and projecting beyond the main face of a noncoring bit. See also: pilot bit; stinger.


Said of the texture of the groundmass of a holocrystalline igneous rock in which lath-shaped microlites (typically plagioclase) are arranged in a glass-free mesostasis and are generally interwoven in irregular unoriented fashion. CF: trachytic. Syn: felty.

pilot bit

A noncoring bit with a cylindrical diamond-set plug of somewhat smaller diameter than the bit proper set in the center and projecting beyond the main face of the bit. See also: plug bit; drag bit.

pilot bob

The weight attached to a shaft plumbline for the purpose of lowering the line down the shaft.

pilot burner

A small burner kept lighted to rekindle the principal burner when desired (as in a flash boiler). The light so maintained is called a pilot light or pilot flame.

pilot drill

A small drill used to start a hole in order to insure a larger drill running true to center.

pilot hole

a. A small hole drilled ahead of a full-sized, or larger borehole.

b. A borehole drilled in advance of mine workings to locate water-bearing fissures or formations. c. A small tunnel driven ahead of, and subsequently enlarged to the diameter required in the following full-size tunnel.

pilot-hole cover

See: cover.

pilot lamp

A small electric bulb that lights when power is turned on in a circuit.

pilot method

The method of excavating a tunnel by driving a small tunnel ahead, and then enlarging its dimensions.

pilot plant

A small-scale processing plant in which representative tonnages of ore can be tested under conditions which foreshadow (or imitate) those of the full-scale operation proposed for a given ore.

pilot reamer

An assemblage of a pilot, a pilot reaming bit, and a reaming barrel. See also: pilot; pilot reaming bit.

pilot reaming bit

A box-threaded, diamond-set, annular-shaped bit designed to be coupled to a pilot and used to ream a borehole to a specific casing size. See also: pilot.

pilot sampling

The taking of preliminary samples of a mineral deposit to study its mode of occurrence and its detailed structure. Syn: reconnaissance sampling.

pilot sequence

Sequence control by means of a pilot cable is effected by means of a low-voltage supply from one contactor panel to the next, or by means of a line voltage pilot cable. Each contactor has an auxiliary contact that controls the supply to the next contactor. In the low-voltage system, the secondary of each potential transformer is earthed at the preceding panel through an auxiliary switch which closes with the contactor. Until these secondary potential transformer circuits are completed, by closing the auxiliary contact, the next conveyor cannot start. See also: sequence starting.

pilot shaft

See: pilot tunnel.

pilot tunnel

A small tunnel or shaft excavated in the center, and in advance of the main drivage, to gain information about the ground and create a free face, thus simplifying the blasting operations.

pilot valve

a. A small balanced valve, operated by a governor or by hand, which controls a supply of oil under pressure to the piston of a servometer or relay connected to a large control valve, which it is desired to operate. Also called relay valve.

b. In a compressor, an automatic valve that regulates air pressure.

pilot wedge

A half-cylinder member, about 5 in (12.7 cm) long, coupled to the lower end of a Hall-Rowe deflection wedge, by means of which the deflection wedge may be oriented in a specific manner in reference to a matching half-cylinder surface on the upper end of the wedge (drive wedge). This is driven into the wooden plug placed about 8 ft (2.4 m) below the point in a borehole where a deflection is to be made. Also called wedge pilot.

Pilz furnace

A circular or octagonal shaft furnace, maintaining or increasing its diameter toward the top, and having several tuyeres; used in smelting lead ores.


A massive or earthy, apple-green, nickel-bearing phyllosilicate; probably willemseite or kerolite having disordered stacking; (Ni,Mg) (sub 6) Si (sub 8) O (sub 20) (OH) (sub 4) .

pimple metal

Crude copper matte of about 78% copper, obtained from the smelting of sulfide copper ores.


a. A marked thinning or squeezing of a rock layer; e.g., a coming-together of the walls of a vein, or of the roof and floor of a coal seam, so that the ore or coal is more or less completely displaced. See also: nip. CF: make; want.

b. A thin place or a narrow part of, an orebody; the part of a mineral zone that almost disappears before it widens out in another place to form an extensive orebody. c. The binding action caused when drillhole walls close in before casing is emplaced, resulting from failure of soft or plastic formations.


A kind of crowbar with a short projection and a heel or fulcrum at the end; a pinch. Used to pry forward heavy objects.


Where a vein narrows, as if the walls had been squeezed in. Where the walls meet, the vein is said to be pinched out. See also: pinching out; pinch.

pinching out

Where a lode or stratum narrows down and disappears. See also: pinch.

pinch out

To taper or narrow progressively to extinction; to thin out.

pinder concentrator

A revolving table on which are tapering spiral copper cleats on a linoleum cover. The tailings are washed over the riffles and off the edge, while the concentrates are delivered at the end of the riffles.


a. A cast roller, designed to keep the haulage rope centered between rail tracks. Spiral grooves on the sides return a straying rope to the central grooves. Works in one direction only.

b. See: line oiler.

pine tar

Very viscous; dark brown to black; liquid or semisolid; strong characteristic odor; sharp taste; translucent in thin layers; hardens with aging; sp gr, 1.03 to 1.07; boiling point, ranges from 240 to 400 degrees C; soluble in alcohol, ether, chloroform, acetone, glacial acetic acid, fixed and volatile oils, and sodium hydroxide; and insoluble in water. Chief constituents are complex phenols; also present are turpentine, rosin, toluene, xylene, and other hydrocarbons. Used in flotation.


An acoustic pulse signal projected by an echo-ranging transducer.


A former name for nontronite. See also: nontronite.


Smaller of a pair of toothed wheels, e.g., the pinion geared to the driven crown wheel of a ball mill.

pinion gear

A drive gear that is smaller than the gear it turns.


A compact, fine-grained, generally impure mica near muscovite in composition; dull-gray, green, or brown; derived from the alteration of other minerals, esp. cordierite, nepheline, scapolite, spodumene, and feldspar.


a. Any high tower or spire-shaped pillar of rock, alone or cresting a summit. A tall, slender, pointed mass; esp., a lofty peak.

b. A sharp pyramid or cone-shaped rock under water or showing above it. c. In alluvial mining, a spine or pillar in limestone bedrock of an irregular and serrated type, in which it is difficult for dredge buckets to work.

pinned coupling

A drill-rod coupling that has been permanently attached to the body of the rod by a metal dowel (or pin) driven into a small hole drilled at the point in the rod where the coupling is screwed into the body of the rod.


a. Boulder clay, from Cumberland, Northumberland, and Lancashire, England, and North Wales.

b. Coarse gravel or sandstone conglomerate.

pin puller

A laborer who removes studs from aluminum reduction pots by operating a motor-driven hydraulic jack.


a. A vanadium ore.

b. A mineral, Ca (sub 2) V (sub 2) O (sub 7) .9H (sub 2) O ; green; forms water-soluble efflorescences; associated with uranium-vanadium deposits of the Colorado Plateau.

pin thread

A thread on the outside surface of a cylindrical or tubular member. Syn: male thread.

pin timbering

A roof support method following two basic principles: (1) that of drilling holes vertically or at an angle into the roof and anchoring roof bolts into a strong firm structure above the lower weak layers, thereby suspending the weak roof on bolts from the strong roof above; and (2) the binding of several layers of weak strata into a beam strong enough to support its weight across the working place. The advantage of pin timbering is that support can be provided at the face without posts being in the way of equipment and more freedom is provided for shuttle cars and other equipment in tramming. See also: timbering; roof bolting.


A vertical pin fastened at the bottom that serves as a center of rotation.

pintle hook

A towing device consisting of a fixed lower jaw, a hinged and lockable upper jaw, and a socket between them to hold a tow ring.


The currently accepted term for a coupling, one end of which is threaded on the outside (pin) and the opposite end threaded on the inside (box). Formerly designated as a male-to-female coupling.


The currently accepted term for a coupling, both ends of which are threaded on the outside. Formerly designated as a male-to-male coupling.

pin-type slat conveyor

Two or more endless chains to which crossbars are attached at spaced intervals, each having affixed to it a series of pointed rods extending in a vertical plane on which work is carried. Used principally in spraying or washing operations where the least amount of area of the product is contacted.


An elementary particle; the contraction of pi-meson. The mass of a charged pion is about 273 times that of an electron. An electrically neutral pion has a mass 264 times that of an electron.

pioneer bench

The first bench in a quarry which is blasted out. It is usually at the top of the rock to be quarried.

pioneer road

A primitive, temporary road built along the route of a job, to provide means for moving equipment and workers.

pioneer wave

U.K. The advance vibration set up by a coal dust explosion. See also: advance wave; shock wave.


See: saponite.


a. A cylindrical, more or less vertical orebody. Syn: chimney; ore pipe; shoot; stock.

b. A vertical conduit through the Earth's crust; e.g., a kimberlite pipe of South Africa, through which magmatic materials have passed. It is usually filled with volcanic breccia and fragments of older rock. As a zone of high permeability, it is commonly mineralized. c. A tubular cavity from several centimeters to a few meters in depth, formed esp. in calcareous rocks, and often filled with sand and gravel; e.g., a vertical joint or sinkhole in chalk, enlarged by solution of the carbonate material and filled with clastic material. See also: piping. d. The name given to the fossil trunks of trees found in coalbeds.

pipe bit

A bit designed for attachment to standard coupled pipe for use in securing the pipe in bedrock. Can be set with diamonds or other abrasive materials.

pipe clamp

a. A device similar to a casing clamp, used in the same manner on pipe as a casing clamp is used on casing. See also: casing clamp.

b. A pipe wrench constructed like a parmalee wrench.

pipe clay

a. Originally a clay suitable for making tobacco pipes, but the term is now used to include any white-burning plastic clay.

b. A mass of fine clay, generally of lenticular form, found embedded in or below a placer gravel bank.

pipe coil

A device which measures only the density of the magnetic components of a slurry. This electromagnetic sensing unit is mounted on a section of rubber or stainless-steel pipe which is installed as a section of the slurry-carrying pipeline. All components are exterior to the pipe, and there is no obstruction to flow. The pipe coil is used widely in magnetic taconite and heavy-media plants. By combining this device with other instruments, it is possible to continuously measure the ore-to-media ratio.

pipe coupling

An internally threaded, short, sleevelike member of ordinary steel used to join lengths of pipe. Sometimes incorrectly called pipe collar; pipe sleeve.

pipe cutter

A tool for cutting wrought iron or steel pipes. The curved end which partly encircles the pipe carries one or more cutting disks.

piped air

Air conducted to workings or a tunnel face through air pipes. See also: auxiliary ventilation.

pipe drivehead

a. A drivehead that is coupled to a pipe. See also: drivehead. Syn: drive collar.

b. Extra thick walled pipe or casing coupling against which the blow of a drive block is delivered when driving or sinking drivepipe or casing. c. An oversize rod or casing coupling on which the blows of a drive block are delivered when casing is being driven or an attempt is being made to jar loose stuck casing or a drill-rod string. d. Incorrectly used as a synonym for drive shoe; drive hammer.

pipe elevator

A device similar to a casing elevator, used to raise and lower outside-coupled pipe in a borehole.

pipe factor

a. Correction made when drilling running ground, alluvial gravels, and sands. The volume actually extracted over a measured depth is compared with that which would be obtained over the true drill pipe area and distance, any discrepancy being due to inrush of sands or forcing out of sand by the pumping action during drilling.

b. The assumed cross-sectional area of a length of borehole when estimating the in situ volume of a core sample. Also called pipe constant.

pipe fitting

A general term referring to any of the ells, tees, various branch connectors, etc., used in connecting pipes.

pipe friction

The drag created on the outside of a pipe being driven into overburden material, which presses and rubs against the outside surface of the pipe and its couplings. See also: skin friction.

pipe grab

A clutch for catching and raising a well pipe.

pipe jack

An iron pipe with a clamp or pigfoot on one end and a curved point on the other. It is wedged between the floor and roof of a mine room to hold the feed chain of a continuous electric coal mining machine.

pipeline transport

Long distance pipeline used for hydraulic transport of coal, gilsonite, copper concentrates and similar materials. See also: hydraulic transport.


a. A person engaged in laying or repairing pipelines. Also called pipefitter.

b. Mine worker who repairs, lengthens, and maintains the pipelines for air and water in mines. c. A worker in charge of a pipe, esp. in hydraulic mining.

pipe prover

An apparatus for testing the tightness of a pipeline or system, usually by hydraulic pressure.


Sometimes applied to a blower of gas in coal mines.

pipe sampler

A device for sampling a pile of ore, consisting simply of a small iron pipe that is driven into the pile and which, when withdrawn, brings a core of ore with it.

pipe sampling

Sampling by means of a drivepipe in accumulations of crushed residues or of material where the larger pieces are not usually greater than 2 in (5.1 cm). The advancing end of the pipe is generally sharpened to provide a cutting edge, and sometimes contracted in diameter so that material once entered will not readily fall out when the pipe is lifted. Also called gun sampling. See also: drivepipe.


See: catlinite.

pipette analysis

The size analysis of fine-grained sediment made by removing samples from a suspension with a pipette.

pipette method

A method for the determination of particle size. See also: Andreasen pipette.


a. In hydraulic mining, discharging water from nozzles at auriferous gravel.

b. The act or process of driving standpipe, drivepipe, or casing into and through overburden. c. Erosion by percolating water in a layer of subsoil, resulting in caving and in the formation of narrow conduits, tunnels, or pipes through which soluble or granular soil material is removed; esp. the movement of material, from the permeable foundation of a dam or levee, by the flow or seepage of water along underground passages. See also: water creep. d. The flow of water under or around a structure built on permeable foundations that will remove material from beneath the structure. e. The tubular depression caused by contraction during cooling, on the top of iron and steel ingots. See also: pipe.


Stream piracy.


An orthorhombic mineral, Na (sub 2) Ca(CO (sub 3) ) (sub 2) .2H (sub 2) O; forms colorless to white short prisms or tablets; in nonmarine evaporites, particularly the Green River oil shales in Wyoming, and Borax Lake, CA.


A blue to green cuproan melanterite (Fe,Cu)SO (sub 4) .7H (sub 2) O .


a. A sedimentary rock, usually a limestone, made up chiefly of pisoliths cemented together; a coarse-grained oolite. Syn: peastone.

b. A term often used for a pisolith, or one of the spherical particles of a pisolite.---Etymol: Greek pisos, pea. CF: oolite. c. An individual unit in a mass of accretionary lapilli.


One of the small, round or ellipsoidal accretionary bodies in a sedimentary rock, resembling a pea in size and shape, and constituting one of the grains that make up a pisolite. It is often formed of calcium carbonate, and some are thought to have been produced by a biochemical algal-encrustation process. A pisolith is larger and less regular in form than an oolith, although it has the same concentric and radial internal structure. The term is sometimes used to refer to the rock made up of pisoliths. CF: oolith.

pisolitic tuff

An indurated pyroclastic deposit composed chiefly of accretionary lapilli or pisolites.


A pistachio-green ferric-iron-rich variety of epidote. Also spelled pistazite.

pistol pipe

In metalworking, the tuyere of a hot-blast furnace.


The working part of a pump, hydraulic cylinder, or engine that moves back and forth in the cylinder; it is generally equipped with one or several rings or cups to control the passage of fluid. It ejects the fluid from the cylinder, as in a pump, or receives force from the fluid, which causes a reciprocating motion, as in an engine.

piston corer

An oceanographic corer containing a piston inside the cylinder which reduces friction by creating suction. There are several varieties, including the Ewing corer, the Mackereth sampler, and the Kullenberg corer. CF: gravity corer.

piston drive-sampler

See: piston sampler.

piston sampler

A drive sampler equipped with either a free or a retractable-type piston that retreats up into the barrel of the sampler in contact with the top of the soil sample as the sampler is pressed into the formation being sampled. CF: drive sampler.

piston speed

Total feet or meters of travel of a piston in 1 min.

piston-type sampler

See: piston sampler.

piston-type washbox

See: plunger-type washbox.