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

oakum
 * Loosely twisted fiber usually of hemp or jute impregnated with tar or with a tar derivative (such as creosote or asphalt); used in caulking seams (such as the wood hulls and decks of ships) and in packing joints (in pipes, caissons, etc.).

Oamaru stone
 * A white, granular limestone found in large quantities in Oamaru, New Zealand, and valued as a building stone.

obduction
 * The overriding or overthrusting of oceanic crust onto the leading edges of continental lithospheric plates; plate accretion. See also: subduction.

object glass
 * See: objective.

objective
 * The lens (or lenses) that gives an image of an object in the focal plane of a microscope or telescope eyepiece. Syn: objective lens; object glass.

objective glass
 * See: objective.

objective lens
 * See: objective.

oblique block
 * A quarry term applied to a block of stone bounded by 3 pairs of parallel faces--4 of the 12 interfacial angles being right angles, 4 obtuse, and 4 acute.

oblique fault
 * A fault that strikes oblique to, rather than parallel or perpendicular to, the strike of the constituent rocks or dominant structure. CF: oblique-slip fault; strike fault; dip fault. Syn: diagonal fault.

oblique illumination method
 * See: van der Kolk method.

oblique joint
 * a. A joint whose strike is oblique to the strike of the strata or metamorphic rocks in which it occurs.

b. A joint that forms an acute angle with dip joints and strike joints.

oblique offset
 * The distance of a point from a main survey line measured at an angle to the latter that is not a right angle. See also: offset.

oblique projection
 * A pictorial view of an object showing its elevation, plan, or section to scale with parallel lines projected from the corners, at 45 degrees or any other angle, indicating the other sides. See also: axonometric projection; isometric projection.

oblique slip
 * In a fault, movement or slip that is intermediate in orientation between the dip slip and the strike slip. CF: strike slip.

oblique-slip fault
 * A fault in which the net slip lies between the direction of dip and the direction of strike. Syn: diagonal-slip fault. CF: oblique fault.

obra
 * The narrow prismatic part of a blast furnace immediately above the crucible.

obsequent fault-line scarp
 * A scarp along a fault line, where the topographically low area is on the upthrown block. CF: resequent fault-line scarp.

observer
 * a. In seismic prospecting, the person in charge of the recording crew, including the shooters and linemen. The observer must maintain the electronic equipment and decide on the best shooting and detector arrangement as well as the best instrumental settings for getting records of optimum quality. The observer operates the recording equipment in the field, often with the help of an assistant. In conventional recording, or in tape recording when photographic monitors are run, the observer or an assistant develops the record in the recording truck immediately after it is shot. Also called operator.

b. In gravity and magnetic prospecting, a person who secures the instrument readings, e.g., on a torsion balance or magnetometer.

obsidian
 * A black or dark-colored volcanic glass, usually of rhyolite composition, characterized by conchoidal fracture. It is sometimes banded or has microlites. Usage of the term goes back as far as Pliny, who described the rock from Ethiopia. Obsidian has been used for making arrowheads, other sharp implements, jewelry, and art objects. Syn: Iceland agate.

obsidianite brick
 * Lightweight, siliceous fireclay, acid-resisting brick, burned to a glasslike mass.

obtuse bisectrix
 * a. That axis that bisects the obtuse angle of the optic axes of biaxial minerals.

b. The angle >90 degrees between the optic axes in a biaxial crystal, bxo. CF: optic angle.

occidental cat's-eye
 * See: cat's-eye; tiger's-eye.

occlude
 * To take in and retain (a substance) in the interior rather than on an external surface; to sorb. Used esp. of metals sorbing gases; e.g., palladium occludes large volumes of hydrogen.

occluded
 * Contained in pores (said of gas occluded in coal).

occluded gas
 * Any of several gases that enter a mine atmosphere from pores, as feeders and blowers, and also from blasting operations. These gases pollute the mine air chiefly by the absorption of oxygen by the coal, and in addition by chemical combination of oxygen with carbonaceous matter, for example, from decaying timbers, rusting of iron rails, burning of lights, and breathing of humans and animals. These gases include oxygen, nitrogen, carbon dioxide, and methane.

occlusion
 * a. Taking up or incorporation of liquids in solids or of gases in liquids.

b. See: absorption.

occupant
 * An occupant of a tract of land, as the word ordinarily is used, is one who has the use and possession thereof, whether he resides upon it or not.

occupation
 * As used in the mining law, it is equivalent to possession, and the right to locate is included in the right to occupy, and incident to a location is the right of possession; but mere occupancy of the public lands and making improvement thereon gives no vested right therein as against a location made in pursuance of law.

occurrence
 * See: mineral occurrence.

ocean current
 * a. The name current is usually restricted to the faster movements of the ocean, while those movements that amount to only a few miles a day are termed drifts.

b. A nontidal current constituting a part of the great oceanic circulation. Examples are gulf stream, kuroshio, and equatorial currents.

oceanic ridge
 * See: Mid-Atlantic Ridge; mid-ocean ridge.

oceanic trench
 * See: trench.

oceanographic dredge
 * Apparatus used aboard ships to bring up quantity samples of the ocean bottom deposits and sediments.

oceanography
 * The broad field of science that includes all fields of study that pertain to the sea. This includes the studies of boundaries of the ocean, its bottom topography, the physics and chemistry of seawater, the characteristics of its motion, and marine biology.

ocher
 * A name given to various native earthy materials used as pigments. They consist essentially of hydrated ferric oxide admixed with clay and sand in varying amounts and in impalpable subdivision. When carrying much manganese ochers grade into umbers. They are either yellow, brown, or red. The best reds are sometimes obtained by calcining the yellow varieties. They are called burnt ochers. Others are obtained by calcining copperas or as a residue from roasting pyrite. In general, the native yellows and browns are varieties of limonite and the native reds are varieties of hematite. One variety of red ocher is known as scarlet ocher. Their value as pigments depends not only on the depth of color but also on the amount of oil required as a vehicle. Syn: terra sienna. CF: umber.

octagon
 * A polygon having eight sides.

octahedral borax
 * A rhombohedral form of hydrous sodium borate, Na (sub 2) B (sub 4) O (sub 7) .5H (sub 2) O, simulating regular octahedrons. From the Lagoong of Tuscany, Italy. See also: tincalconite. Syn: borax.

octahedral cleavage
 * In the isometric system, cleavage parallel to the faces of an octahedron.

octahedral copper
 * See: cuprite.

octahedral iron ore
 * See: magnetite.

octahedrite
 * a. A class of meteorites.

b. The most common iron meteorite contains 6% to 18% nickel in the metal phase; on etching, shows Widmanstaetten structure owing to the presence of intimate intergrowths (of plates of kamacite with narrow selvages of taenite) oriented parallel to the octahedral planes. c. A former name for anatase. See also: titanium dioxide.

octahedron
 * a. A closed crystallographic form with isometric symmetry and eight faces, each an equilateral triangle; sometimes called a regular octahedron to distinguish it from the more general usage defined below. Commonly observed in isometric minerals, such as fluorite, pyrite, magnetite, and diamond.

b. Less precisely, a closed crystallographic form composed of (or bounded by) eight triangular surfaces (a bipyramid), such as in some samples of anatase. Plural: octahedra. Adj.: octahedral.

octant
 * Each eighth of crystal space divided by three noncoplanar axial planes. CF: dodecant.

octant search
 * Used to limit the number of sample data points used for estimating intermediate spatial values. The search neighborhood is divided into eight equal-angle sectors. Constraints on selection of data values to include in the estimation include: minimum and maximum of samples or the number of consecutive empty sectors. If either criteria is below minimum, an interpolated value is not calculated. Applies to any interpolation method where a limited number of sample data points are used to estimate intermediate values.

octaphyllite
 * a. A trioctahedral clay mineral.

b. A group of mica minerals that contains eight cations per ten oxygen and two hydroxyl ions. c. Any mineral of the octaphyllite group, such as biotite; a trioctahedral clay mineral. CF: heptaphyllite.

octopus
 * A bin or tank to facilitate the concrete lining of circular shafts. The concrete is mixed on the surface, taken down the shaft in buckets, and discharged into the octopus. The concrete is then led away through flexible rubber pipes to different points around the shaft.

ocular
 * Eyepiece of a microscope.

O'Donaghue formula
 * A formula used for calculating the thickness of tubbing: t = hdF/2C + A, where: t is the required thickness of tubbing in inches; h is the pressure of water in pounds per square inch; d is the diameter of the shaft in inches; C is the crushing strength of cast iron in pounds per square inch, which may be taken as 95,000; F is the factor of safety adopted between 5 and 10; and A is the allowance for possible flaws and corrosion and may vary from 1/4 to 1 in (6.4 to 25.4 mm), averaging 1/2 in (12.7 mm).

O'Donahue's theory
 * A mine subsidence theory based on an extension of the theory of the normal. In it, subsidence is regarded as taking place in two stages. There is, first, a breaking of the rocks in which the lines of fracture tend to run at right angles to the stratification. This is followed by an aftersliding, or inward movement from the sides, resulting in a pull or draw beyond the edges of the workings.

odontolite
 * A fossil bone or tooth colored deep blue by iron phosphate (vivianite), and rarely green by copper compounds, and resembling turquoise, such as that from the tusks of mammoths found in Siberia. It is cut and polished for jewelry. Syn: bone turquoise; fossil turquoise.

oersted
 * a. The practical, cgs electromagnetic unit of magnetic intensity. A unit magnetic pole, placed in a vacuum in which the magnetic intensity is 1 Oe (79.577 A/m), is acted upon by a force of 1 dyn in the direction of the intensity vector.

b. Commonly used as the cgs unit of magnetic-field intensity. Except in magnetized media, a magnetic field with an intensity (H) of 1 Oe has an induction (B) of 1 Gs (0.1 mT).

Oetling freezing method
 * A method of shaft sinking by freezing wet ground in sections as the sinking proceeds. The permanent lining is also inserted as the shaft is sunk. The freezing equipment is a cylinder equal in diameter to the shaft and 44 in. (1.12 m) in height, with the lower end closed by a plate. The cylinder is in sections, each of which can be removed. Each section is provided with freezing coils. After freezing the ground, two sections are removed, the ground is thawed locally and removed, and a segment of the permanent lining is inserted. The process is repeated. See also: Dehottay process; freezing method.

offcenter waterway
 * A waterway port in a noncoring diamond bit, not located in the center of the bit face.

off gate
 * N. of Eng. One of the goaf roadways in longwall workings, which are set about 120 yd (110 m) apart.

off-highway truck
 * A truck of such size, weight, or dimensions that it cannot be used on public highways.

official plat of survey
 * The expression in a patent according to the official plat of survey of the land returned to the general land office by the surveyor general refers to the description of the land as well as to the quantity conveyed.

off line
 * a. A condition existing when the drive rod of the drill swivel head is not centered and parallel with the borehole being drilled.

b. A borehole that has deviated from its intended course. c. A condition existing wherein any linear excavation (shaft, drift, borehole, etc.) deviates from a previously determined or intended survey line or course.

off-peak load
 * Electricity drawn at a period when the power station that supplies it is not fully loaded.

offretite
 * A hexagonal mineral, (K (sub 2) ,Ca) (sub 5) Al (sub 10) Si (sub 26) O (sub 72) .30H (sub 2) O ; zeolite group; commonly intergrown with erionite and levyne as a vein or cavity filling in mafic lavas.

offset
 * a. A short drift or crosscut driven from a main gangway or level.

b. The horizontal distance between the outcrops of a dislocated bed. c. Of a fault, the horizontal component of displacement, measured perpendicular to the disrupted horizon. See also: normal shift. d. A side (horizontal) measurement of distance perpendicular to a line, usually a transit line. e. To collar and drill a borehole at some distance from the designated site to avoid a difficult setup. f. To drill a borehole near one previously drilled, which may have been lost, for purposes of correlation or to determine the lateral extent of mineralization. g. An abrupt change in the trend of a drill hole, usually caused by a small shelflike projection of rock alongside one wall of the drill hole. h. A well drilled near the boundary of a lease opposite a completed well on an adjacent lease. Syn: offset hole; offset well. i. To offset a well by drilling the next adjoining location in accordance with a spacing pattern. j. A spur or minor branch from a principal range of hills or mountains. k. The distance along the strain coordinate between the initial portion of a stress-strain curve and a parallel line that intersects the stress-strain curve at a value of stress which is used as a measure of the yield strength. It is used for materials that have no obvious yield point. A value of 0.2% is commonly used.

offset deposit
 * a. A mineral deposit, esp. of sulfides, formed partly by magmatic segregation and partly by hydrothermal solution, near the source rock.

b. At Sudbury, ON, Canada, the term refers to dikelike bodies radiating from the Sudbury Complex, thought to have been filled from above by xenolithic rock fragments and massive pyrrhotite-chalcopyrite-pentlandite.

offset digging
 * In a ladder ditcher, digging with the boom not centered in the machine.

offset hole
 * See: offset.

offset line
 * In surveying, a line established parallel to the main survey line, and usually not far from it; e.g., a line on a sidewalk, 2 ft (0.6 m) from the established street line, or a line parallel to the centerline of a bridge and 50 ft (15.2 m) from it.

offset ridge
 * A ridge that is discontinuous because of faulting.

offset staff
 * In surveying, a rod, usually 10 links (0.2012 m) long, used in measuring short offsets.

offset well
 * See: offset.

off-sider
 * A driller or drill-crew-worker working on the opposite shift. Also called drill helper.

offtake
 * A length of boring rods unscrewed and detached at the top of a borehole. Also called rod stand; setout.

offtake lad
 * See: shackler.

offtake rod
 * One of the auxiliary rods at the top of a winding shaft for guiding and steadying the cages during decking or loading and unloading operations.

off-the-road hauling
 * Hauling that takes place off the public highways, generally on a mining or excavation site. The hauling units used are generally higher and wider than those used in over-the-road hauling since highway restrictions do not limit size, weight, etc. CF: over-the-road hauling.

off the solid
 * In this type of blasting, coal is blasted from the solid with no precutting or shearing.

ogie
 * The space before the fire in a kiln. Also called killogie.

ohm
 * The practical mks unit of electric resistance that equals the resistance of a circuit in which a potential difference of 1 V produces a current of 1 A; the resistance in which 1 W of power is dissipated when 1 A flows through it. The standard in the United States. Symbols, Omega and omega.

ohmmeter
 * A type of galvanometer that directly indicates the number of ohms of the resistance being measured.

Ohm's law
 * The formula expressing Ohm's law is I = E/R, in which I is the electric current in amperes; E is the electromotive force in volts; and R is the resistance in ohms.

-oid
 * A suffix meaning "in the form of."

oikocryst
 * In poikilitic fabric, the enclosing crystal.

oil agglomeration
 * A coal beneficiation process in which an oil is used to preferentially wet the coal particles, which have an affinity to agglomerate into masses that are then selectively removed by screening, e.g. See also: selective agglomeration.

oil base
 * The residuum from the distillation of petroleum. When paraffin is obtained from petroleum, the original oil is said to have a paraffin base; when the residue is entirely asphaltic, the original petroleum is said to have an asphaltic base. Some petroleums have both an asphaltic and a paraffin base.

oil-bearing shale
 * Shale impregnated with petroleum. Not to be confused with oil shale.

oiled
 * A term used in flotation when a particle is given a water repellent surface. When such a coating has been formed, the particle is said to be oiled or treated and ready to be floated.

oiler
 * a. In flotation, oil that provides a film around a mineral particle.

b. One of several types of mechanical devices that deliver oil to machines and into air or steam lines in controllable amounts. Also called atomizer; line oiler; lubricator; oil pot; pineapple; pot.

oilfield winch
 * An extremely powerful low-speed winch on a crawler tractor.

oil flotation
 * A process in which oil is used in ore concentration by flotation. Syn: flotation process.

oil of vitriol
 * Concentrated sulfuric acid.

oil pot
 * See: line oiler; oiler.

oil pump
 * A hydraulic pump supplying oil under pressure to the hydraulic-feed cylinders and pistons of a hydraulic-type swivel head on a diamond drill.

oil shale
 * A kerogen-bearing, finely laminated brown or black sedimentary rock that will yield liquid or gaseous hydrocarbons on distillation. CF: bituminous shale. Syn: kerogen shale; petroleum-oil cannel coal; petrolo-shale.

oilstone
 * A fine-grained stone used for sharpening edged tools or other similar metal surfaces.

oil-temper
 * To harden steel by quenching in oil after heating.

okenite
 * A triclinic mineral, Ca (sub 10) Si (sub 18) O (sub 46) .18H (sub 2) O ; white; fibrous; commonly associated with zeolites in basalts.

old age
 * a. The stage in the development of a stream at which erosion is decreasing in vigor and efficiency, and aggradation becomes dominant as the gradient is reduced. It is characterized by a broad open valley with a flood plain that may be 15 times the width of the meander belt; numerous oxbows, bayous, and swamps; a sluggish current; and slow erosion, effected chiefly by mass-wasting at valley sides.

b. The final stage of the cycle of erosion of a landscape or region, in which the surface has been reduced almost to base level and the landforms are marked by simplicity of form and subdued relief. It is characterized by a few large meandering streams flowing sluggishly across broad flood plains, separated by faintly swelling hills, and having dendritic distributaries; and by peneplanation. c. A hypothetical stage in the development of a coast, characterized by a wide wave-cut platform, a faintly sloping sea cliff pushed far inland, and a coastal region approaching peneplanation. The stage is probably a theoretical abstraction, since it is doubtful whether stability of sea level is maintained long enough for the land to be so reduced.

oldhamite
 * An isometric mineral, (Ca,Mn)S ; pale brown; occurs in some meteorites and slags; rapidly oxidizes in contact with air.

Oldham stone duster
 * A self-contained transportable stone duster. A high-velocity current of air from a fan or blower is mechanically fed from a hopper above, both the fan and the feeding mechanism being driven from the tub axle as it is drawn along by rope haulage, horse, or manually. It delivers about 3/4 lb (0.34 kg) of dust per yard (0.9 m) of travel.

Oldham-Wheat lamp
 * A cap lamp designed for full self-service. This lamp, weighing 6-5/8 lb (3.0 kg), has a 4-V lead-acid battery in a hard rubber case with covers of stainless steel or nickel-plated hard brass. The switch is magnetically operated and is situated in a sealed plastic moulding. A 4-W bulb burning 11 h or a 2-W bulb burning 14 h is used. The lamp is of one-piece construction and no dismantling is needed to charge the accumulator.

old hole
 * See: main hole.

oldland
 * a. Any ancient land; specif. an extensive area (such as the Canadian shield) of ancient crystalline rocks reduced to low relief by long-continued erosion and from which the materials of later sedimentary deposits were derived.

b. A region of older land, behind a coastal plain, that supplied the material of which the coastal-plain strata were formed. c. A term proposed by Maxson and Anderson (1935) for the land surface of the old-age stage of the cycle of erosion, characterized by subdued relief.

Old Red Sandstone
 * A thick sequence of nonmarine, predominantly red sedimentary rocks, chiefly sandstones, conglomerates, and shales, representing the Devonian System in parts of Great Britain and elsewhere in northwestern Europe.

old scrap
 * Scrap derived from consumer goods that have outlived their usefulness in the economy; it includes discarded white goods, automobiles, electrical equipment, machinery, etc.

old silver
 * Silver made to appear old by the application of graphite and grease.

old waste
 * Scot. Old or abandoned workings.

old working
 * Mine working that has been abandoned, allowed to collapse, and perhaps sealed off. Unless proper safeguards are taken, old workings can be a source of danger to workings in production particularly if they are waterlogged and their plan position is uncertain. See also: inrush of water.

oleander-leaf texture
 * Leaf-shaped masses of stromeyerite (or other minerals) in a matrix of chalcocite (or other mineral).

oleic acid
 * Ch (sub 3) (CH (sub 2) ),CH:CH(CH (sub 2) ) (sub 7) COOH ; a mono-unsaturated fatty acid used in ore flotation; insoluble in water; and soluble in alcohol, ether, and in most other organic solvents.

oligist
 * See: hematite.

oligist iron
 * See: hematite. Also spelled oligiste iron.

Oligocene
 * An epoch of the early Tertiary Period, after the Eocene and before the Miocene; also, the corresponding worldwide series of rocks. It is considered to be a period when the Tertiary is designated as an era.

oligoclase
 * A triclinic mineral, (Na,Ca)[(Si,Al)AlSi (sub 2) O (sub 8) ] ; plagioclase series of the feldspar group; has NaSi (albite) 10 to 30 mol % and CaAl (anorthite) 90 to 70 mol %; pseudomonoclinic with prismatic cleavage and characteristic polysynthetic twinning commonly visible on cleavage traces; white; may be chatoyant; a common rock-forming mineral in igneous and metamorphic rocks of intermediate to high silica content; forms the entire mass in some anorthosites; less commonly a vein mineral.

oligonite
 * A former name for manganoan siderite, (Fe,Mn)CO (sub 3).

oligosiderite
 * A meteorite containing a small amount of metallic iron.

oligotrophic peat
 * Peat poorly supplied with nutrients.

olivenite
 * An orthorhombic mineral, Cu (sub 2) AsO (sub 4) (OH) ; adamantine to vitreous; a secondary mineral in copper deposits.

Oliver filter
 * A continuous-type filter made in the form of a cylindrical drum with filter cloth stretched over the convex surface of the drum. The drum rotates slowly about a horizontal axis, and the lower part is immersed in a tank containing the pulp to be filtered. Arrangement of pressure and suction pipes on the interior of the drum permits the application of suction to the filtering surface. As the filter passes through the tank, it picks up a layer of solid material and emerges carrying a layer of filter cake. Syn: continuous filter.

olivine
 * A mineral group including fayalite, Fe (sub 2) SiO (sub 4) ; forsterite, Mg (sub 2) SiO (sub 4) ; liebenbergite, (Ni,Mg) (sub 2) SiO (sub 4) ; and tephroite, Mn (sub 2) SiO (sub 4) ; orthorhombic; olive green, grayish green, brown, or black; members intermediate in the forsterite-fayalite crystal solution series are common rock-forming minerals in gabbros, basalts, peridotites, and dunites; alters hydrothermally to serpentine. Fayalite occurs in some granites and syenites, forsterite in thermally metamorphosed dolomites, and tephroite in iron manganese ore deposits and their associated skarns. Syn: peridot; chrysolite; olivinoid.

olivine rock
 * See: dunite.

olivinite
 * a. In the International Union of Geological Sciences classification, Syn: dunite.

b. An olivine-rich ore-bearing igneous rock that also contains other pyroxenes and/or amphiboles. Syn: leucochalcite.

olivinoid
 * An olivinelike substance found in meteorites. See also: olivine.

olivinophyre
 * Porphyry containing olivine phenocrysts.

ollenite
 * A type of hornblende schist characterized by abundant epidote, sphene, and rutile. Garnet is one of the accessories.

O.L.P. steel process
 * A steelmaking method similar to the L.D. except that powdered lime is blown with the oxygen stream (therefore, the letters O.L.P.--oxygen- lime-powder). See also: L.D. steel process; oxygen-Bessemer.

ombrogenous peat
 * Peat, the nature of which is determined by the amount of rainfall.

omnibus
 * In glassmaking, a sheet-iron cover to protect, from drafts, the glass articles in a leer.

omnidirectional hydrophone
 * A hydrophone whose response is essentially independent of angle of arrival of the incident sound wave.

omphacite
 * A mineral of the pyroxene group intermediate among aegirine, jadeite, and augite; i.e., high in aluminum and sodium, and of high-pressure origin; monoclinic; pale to grass green; occurs in eclogites.

o.m.s.
 * a. Output (usually in hundredweights) per manshift. It is a method of expressing the productivity of mines, miners, and management.

b. N. of England. Output (usually tons) per manshift. Interpretation depends on the basis for calculating manshifts, e.g., face o.m.s. is based on manshifts at the face; seam o.m.s. on piecework and bargain work manshifts in the seam; overall (pit) o.m.s. on all manshifts underground, including datal labor.

on air
 * a. The state of a pump which is operating although having no liquid in its working parts.

b. Scot. Said of a pump when air is drawn at each stroke.

oncosimeter
 * An instrument for determining the specific gravity of a molten metal by the immersion of a ball made of another metal and of known weight.

onegite
 * A variety of goethite.

one on two
 * A slope in which the elevation rises 1 ft (m) in 2 horizontal ft (m).

one-part line
 * A single strand of rope or cable.

one-piece set
 * A term applied to a single stick of timber, called a post, stull, or prop. Post and prop are applied to vertical timbers, and stull is applied to inclined timbers, or those placed horizontally. See also: set.

one shot
 * a. A borehole-survey instrument that records a single inclination and/or bearing reading on each round trip into a borehole.

b. Single shot.

one-shot exploder
 * See: Little Demon exploder.

one-spot strip mining
 * Consists of three operations: the top material is cast out of the way; pay material is dug and trucked away; and the top is pushed or cast back in.

one-way ram
 * A hydraulic cylinder in which fluid is supplied to one end so that the piston can be moved only one way by power. Syn: single-acting ram.

one-way ventilation
 * See: peripheral ventilation.

onion-skin weathering
 * See: spheroidal weathering.

onlap
 * a. An overlap characterized by the regular and progressive pinching out, toward the margins or shores of a depositional basin, of the sedimentary units within a conformable sequence of rocks, in which the boundary of each unit is transgressed by the next overlying unit and each unit in turn terminates farther from the point of reference. Also, the successive extension in the lateral extent of strata (as seen in an upward sequence) due to their being deposited in an advancing sea or on the margin of a subsiding landmass. Ant: offlap. Syn: transgressive overlap. CF: overlap.

b. The progressive submergence of land by an advancing sea. CF: transgression.

on line
 * a. A linear underground excavation advancing in compliance with a predetermined surveyed direction or line.

b. A borehole the course of which is not deviating from the intended direction. c. Said of a diamond drill when its drive rod is centered on and parallel to a borehole.

on long awn
 * A face between end and crosscut.

onofrite
 * A former name for selenian metacinnabar Hg(S,Se).

on plane
 * Scot. In a direction at right angles to, or facing, the plane or main joints. Syn: plane course.

onsetter
 * pit bottom, and also the signaling to the pithead. In modern mines, the onsetter is stationed in a cabin and all controls are within reach for the loading and unloading of the cages, shaft signaling, and other car control equipment at the shaft bottom. See also: cager; hitcher.

b. The person in charge of winding operations underground, who is stationed at the shaft side and gives all signals to the winding engineman.

onsetting machine
 * Eng. A mechanical apparatus for loading cages with full tubs and discharging the empties, or vice versa, at one operation.

on short awn
 * A face in a direction between bord and crosscut.

on sights
 * a. Following sights placed by a surveyor.

b. On line.

Ontarian
 * a. Stage in New York State: Middle Silurian (middle and lower parts of Clinton Group).

b. An obsolete name for the Middle and Upper Ordovician in New York State.

on-the-solid
 * a. Applied to a blasthole extending into coal farther than the coal can be broken by the blast.

b. That part of a blasthole that cannot be broken by the blast. c. A practice of blasting coal with heavy charges of explosives, in lieu of undercutting or channeling.

on the track
 * Diamonds inset in the crown of a bit in concentric circles so that the diamonds in any one circle follow the same groove cut into the rock.

onyx
 * a. A chalcedonic variety of quartz with color, chiefly white, yellow, red, or black, in straight parallel bands; used esp. in making cameos. See also: banded agate; agate; chalcedony; sardonyx; jasponyx. CF: onyx agate.

b. A name applied incorrectly to dyed, unbanded, solid-color chalcedony; esp. black onyx. c. Adj. Parallel banded; e.g., onyx marble and onyx obsidian. d. Jet black translucent layers of calcite from cave deposits, often called Mexican onyx or onyx marble. See also: travertine.

onyx agate
 * Banded agate with straight parallel layers of differing tones of gray; not a syn. for onyx. CF: onyx.

onyx marble
 * Translucent, generally layered, cryptocrystalline calcite with colors in pastel shades, particularly yellow, brown, and green. See also: cave onyx; Egyptian alabaster; oriental alabaster; Mexican onyx; travertine.

oolite
 * a. A sedimentary rock, usually a limestone, made up chiefly of ooliths cemented together. The rock was originally termed "oolith." Syn: roestone; eggstone.

b. A term often used for oolith, or one of the ovoid particles of an oolite. Etymol. Greek oon, egg. CF: pisolite.

oolith
 * One of the small round or ovate accretionary bodies in a sedimentary rock, resembling the roe of fish, and having diameters of 0.25 to 2 mm (commonly 0.5 to 1 mm). It is usually formed of calcium carbonate, but may be of dolomite, silica, or other minerals, in successive concentric layers, commonly around a nucleus such as a shell fragment, an algal pellet, or a quartz-sand grain, in shallow, wave-agitated water; it often shows an internal radiating fibrous structure indicating outward growth or enlargement at the site of deposition. CF: pisolith. Syn: oolite; ovulite.

oolitic
 * Pertaining to an oolite, or to a rock or mineral made up of ooliths; e.g., an oolitic ironstone, in which iron oxide or iron carbonate has replaced the calcium carbonate of an oolitic limestone.

oolitic limestone
 * An even-textured limestone composed almost wholly of relatively uniform calcareous ooliths, with virtually no interstitial material. It is locally an important oil reservoir (such as the Smackover Formation in Arkansas), and is also quarried for building stone.

oolitic texture
 * The texture of a sedimentary rock consisting largely of ooliths showing tangential contacts with one another.

ooze
 * a. A soft, slimy, sticky mud.

b. To emit or give out slowly. c. A fine-grained pelagic deposit that contains more than 30% of material of organic origin. d. An unconsolidated deposit composed almost entirely of the shells and undissolved remains of foraminifera, diatoms, and other marine life; diatom ooze and foraminiferal ooze.

opacite
 * A general term applied to swarms of opaque, microscopic grains in rocks, esp. as rims that develop mainly on biotite and hornblende phenocrysts in volcanic rocks, apparently as a result of post-eruption oxidation and dehydration. Opacite is generally supposed to consist chiefly of magnetite dust. CF: ferrite.

opacity
 * The quality of being opaque. See also: opaque.

opal
 * An amorphous or microcrystalline mineral, SiO (sub 2) .nH (sub 2) O ; may be tridymite or cristobalite; has a varying proportion of water (as much as 20% but commonly 3% to 9%); occurs in nearly all colors; transparent to nearly opaque; typically shows a marked iridescent "play of color"; differs from quartz in being isotropic; has a lower refractive index than quartz and is softer, more soluble, and less dense; generally occurs massive and may be pseudomorphous after other minerals; deposited at low temperatures from silica-bearing water; occurs in cracks and cavities of igneous rocks, in flintlike nodules in limestones, in mineral veins, in deposits of thermal springs, in siliceous skeletons of various marine organisms (such as diatoms and sponges), in serpentinized rocks, in weathering products, and in most chalcedony and flint. The transparent colored varieties exhibiting opalescence are valued as gemstones. Syn: opalite. See also: opaline.

opalescence
 * A milky or somewhat pearly appearance or luster of a mineral, such as that shown by opal and moonstone. CF: play of color.

opaline
 * a. Any of several minerals related to or resembling opal; e.g., a pale-blue to bluish-white opalescent or girasol corundum, or a brecciated impure opal pseudomorphous after serpentine.

b. An earthy form of gypsum. c. A rock with a groundmass or matrix consisting of opal. adj. Resembling opal, esp. in appearance; e.g., opaline feldspar (labradorite) or opaline silica (tabasheer).

opalite
 * See: opal.

opalized wood
 * Silicified wood. See also: wood opal.

opaque
 * Said of a material that is impervious to visible light or has metallic luster. CF: transopaque; translucent; transparency; transparent; opacity

opaque-attrite
 * Attritus that is opaque in thin sections. Syn: opaque-durit.

opaque attritus
 * Refers to coal material of which the most prominent and important constituent is opaque matter and also referred to as opaque matrix, black fundamental matter or matrix and residuum.

opaque-durit
 * See: opaque-attrite.

open area
 * See: effective screening area.

opencast
 * A working in which excavation is performed from the surface. Commonly called open pit. See also: bench; quarry. CF: strip mine. Syn: opencut; opencut mine.

opencast method
 * A mining method consisting of removing the overlying strata or overburden, extracting the coal, and then replacing the overburden. When the overlying material consists of earth or clay it can be removed directly by scrapers or excavators, but where rock is encountered it is necessary to resort to blasting to prepare the material into suitable form for handling by the excavators. See also: strip mining.

opencast mine
 * See: opencast.

opencast working
 * See: opencast; strike working.

open circuit
 * In mineral dressing, a flow line in which the solid particles pass from one appliance to the next without being screened, classified, or otherwise checked for quality; no fraction is returned for retreatment.

open-circuit mill
 * A grinding mill without classifiers.

open-crib timbering
 * Shaft timbering with cribs alone, placed at intervals.

opencut
 * a. To increase the size of a shaft when it intersects a drift so as to form a puddle wall behind the sets of timber.

b. Open pit; surface working in which the working area is kept open to the sky. See also: opencast. Syn: strip mine.

opencut mine
 * An excavation for removing minerals which is open to the weather. See also: opencast.

opencut mining
 * See: surface mining; openpit mining.

open-drive sampler
 * A drive-type soil-sampling device that is essentially a headpiece, threaded to fit a drill rod, to which is attached a removable length of thin-wall brass or steel tubing. An example is the Shelby tube.

open end method
 * A method of mining pillars in which no stump is left; the pockets driven are open on the goaf side and the roof is supported on timbers.

opener hole
 * The first hole or holes fired in a round blasted off the solid to create an additional free face in a coal mine.

open fault
 * A fault in which the two walls are separated. CF: closed fault.

open fire
 * Fire occurring in a roadway or at the coal face in a mine. Such fires may or may not be easily accessible. They may be in the roof of a roadway or seam, or in the kerf of a machine-cut face. However, they are quite distinct in their initiation from gob fires. An open fire may be ignited by a blown-out shot, electrical failure, or from sparks produced by friction. See also: spontaneous combustion.

open fold
 * A fold in which the limbs diverge at a large angle.

open front
 * The arrangement of a blast furnace with a forehearth.

open-graded aggregate
 * Mineral aggregate containing very few small particles so that the void spaces are relatively large.

open hearth
 * The form of regenerative furnace of the reverberatory type used in making steel by the Martin, Siemens, and Siemens-Martin processes. See also: furnace; open-hearth furnace.

open-hearth furnace
 * A reverberatory melting furnace with a shallow hearth and a low roof. The flame passes over the charge on the hearth, causing the charge to be heated both by direct flame and by radiation from the roof and sidewalls of the furnace. In the ferrous industry, the furnace is regenerative. See also: open hearth.

open-hearth process
 * A process for manufacturing steel, either acid or basic, according to the lining of the reverberatory furnace, in which selected pig iron and malleable scrap iron are melted, with the addition of pure iron ore. The latter, together with the air, contributes to the oxidation of the silicon and carbon in the melted mass. The final deoxidation is sometimes produced by the addition of a small quantity of aluminum or ferromanganese, which at the same time desulfurizes and recarburizes the metal to the required extent. See also: L.D. steel process; Siemens-Martin process.

open-hearth steel
 * See: open-hearth process.

open hole
 * a. Coal or other mine workings at the surface or outcrop. Also called opencast; opencut; open pit.

b. A borehole that is drilled without cores. c. Uncased portion of a borehole. d. A borehole free of any obstructing object or material.

opening
 * a. A widening out of a crevice, in consequence of a softening or decomposition of the adjacent rock, so as to leave a vacant space of considerable width.

b. A short heading driven between two or more parallel headings or levels for ventilation. c. Surface entrance to mine workings. Syn: mine opening.

opening out
 * The formation of a longwall face by driving headings and cross headings and connecting the faces to form a continuous line of coal face. It may be viewed as the final stage in development, leading to full coal production. In pillar-and-stall mining, opening out would imply the setting off of the main headings and subsidiary drivages for the formation of coal pillars. See also: branch headings; mechanized heading development.

openings
 * a. The parts of coal mines between the pillars, or the pillars and ribs.

b. A series of parallel chambers or openings, separated by pillars or walls, in slate mining. The width of an opening varies from 35 to 50 ft (11 to 15 m) depending on roof conditions.

opening shot
 * In blasting into solid rock, the wedging shot, gouging shot, or burn cut. Leading shot fired to open up the rock face by creating a cavity and therefore easing the work done by later shots in a round.

opening stock
 * Quantity on hand at start of accounting period--ore, concentrates, stores, etc.

open lagging
 * Lagging placed a few inches apart.

open light
 * A naked light. Not a safety light.

open off
 * a. To turn stalls off stalls, or to drive branch roadways from crossheadings.

b. Eng. To begin the longwall system from the shaft pillar, or the far end of the royalty, or from any headings previously driven out for the purpose of commencing such system. c. To start any new working, as a heading, entry, gangway, room, etc., from another working, as a slope, gangway, etc.

openpit mine
 * A mine working or excavation open to the surface. See: strip mine.

openpit mining
 * a. A form of operation designed to extract minerals that lie near the surface. Waste, or overburden, is first removed, and the mineral is broken and loaded, as in a stone quarry. Important chiefly in the mining of ores of iron and copper.

b. The mining of metalliferous ores by surface-mining methods is commonly designated as openpit mining as distinguished from the strip mining of coal and the quarrying of other nonmetallic materials such as limestone, building stone, etc. See also: strip mining.

openpit quarry
 * A quarry in which the opening is the full size of the excavation. One open to daylight.

open pot
 * Fireclay pot for melting glass--open at the top.

open rock
 * Any stratum sufficiently open or porous to contain a significant amount of water or to convey it along its bed.

opens
 * Large, open cracks or crevices and small and large caverns.

open-sand casting
 * Casting made in a mold simply excavated in sand, without a flask.

openset
 * Scot. An unfilled space between pack walls. See also: cundy.

open shop
 * A shop, or mine, where the union price is paid, but where the workers are not all union members. CF: union shop.

open split
 * A split in which no regulator is installed. Syn: free split.

open stope
 * a. An unfilled cavity.

b. Underground working place either unsupported, or supported by timbers or pillars of rock.

open-stope method
 * a. Stoping in which no regular artificial method of support is employed, although occasional props or cribs may be used to hold local patches of insecure ground. The walls and roof are self-supporting, and open stopes can be used only where the ore and wall rocks are firm.

b. See: overhand stoping.

open-tank method
 * A method of treating mine timber to prevent decay in which the timber is immersed in a tank of hot preservative and then in a tank of cold preservative. The preservatives used are creosote, zinc chloride, sodium fluoride, and other chemicals. See also: timber preservation; Bethell's process.

open timbering
 * The usual method of setting timber or steel supports in mines--they are spaced from 2 to 5 ft (0.6 to 1.5 m) apart, with laggings and struts to secure the ground between each set. The method is used in ground that does not crumble or flow. See also: close timbering.

open-top carrier
 * The main use of this type of bucket elevator has been in handling the product of the larger crushers. Steel buckets of large capacity, which may be as long as 7 ft (2.1 m), are attached rigidly to a heavy flat bar chain, each strand made of two bars with a pitch of 2 and with self-oiling flanged rollers at each intersection. The elevator rises at an angle of about 60 degrees, and the rollers run on ways made of light T-rails. The buckets have overlapping edges, so that there is no spill between them.

open-top tubbing
 * A length of tubbing having no wedging crib on the top of it.

open traverse
 * A surveying traverse that starts from a station of known or adopted position but does not terminate upon such a station and therefore does not completely enclose a polygon. CF: closed traverse.

open working
 * Surface working, e.g., a quarry or opencast mine. Among the minerals often exploited by open workings are coal, brown coal, gems; the ores of copper, gold, iron, lead, and tin; and all kinds of stone. Also called open work.

operating carrier
 * The mechanism used with the automatic duckbill through which the extension and retraction of the shovel trough are controlled.

operating cost
 * The sum of the costs of mining, beneficiation, and administration gives the operating cost of a mine.

operating engineer
 * See: hoistman.

operating point
 * A ventilation system is composed of a fan and a set of connected ducts. In a mine ventilation system, mine openings comprise the ducts. At a given air density and with the fan operating at constant speed, there is only one head and quantity of airflow that can result. This is an equilibrium condition and is known as the operating point of the system.

operation
 * In crystallography, the rotation, reflection, or inversion of an attribute of a crystal structure to complete its symmetry. CF: element.

operational capacities
 * Figures given on flowsheets to indicate quantities passing various points in plant per unit time, taking account of fluctuations in the rate of supply and composition (as to size and content of impurity), as follows: (1) design capacity, the rate of feed, defined by limits expressing the extent and duration of load variations, at which specific items of plant subject to a performance guarantee must operate continuously and give the guaranteed results on a particular quality of feed; (2) peak design capacity, a rate of feed in excess of the design capacity, which specific items of plant will accept for short periods without fulfilling the performance guarantees given in respect of them; and (3) mechanical maximum capacity, the highest rate of feed at which specific items of equipment, not subject to performance guarantees, will function on the type and quality of feed for which they are supplied.

operative temperature
 * Operative temperature is that temperature of an imaginary environment in which, with equal wall (enclosing areas) and ambient air temperatures and some standard rate of air motion, the human body would lose the same amount of heat by radiation and convection as it would in some actual environment at unequal wall and air temperatures and for some other rate of air motion.

ophicalcite
 * A recrystallized metamorphic rock composed of calcite and serpentine, commonly formed by dedolomitization of a siliceous dolostone. Some ophicalcites are highly veined and brecciated and are associated with serpentinite.

ophiolite
 * A group of mafic and ultramafic igneous rocks ranging from spilite and basalt to gabbro and peridotite, including rocks rich in serpentine, chlorite, epidote, and albite derived from them by later metamorphism, whose origin is associated with an early phase of the development of a geosyncline. The term was originated by Steinman in 1905.

ophite
 * A general term for diabases that have retained their ophitic structure although the pyroxene is altered to uralite. The term was originated by Palasson in 1819.

ophitic
 * Applied to a texture characteristic of diabases or dolerite in which euhedral or subhedral crystals of plagioclase are embedded in a mesotasis of pyroxene crystals, usually augite. Also said of a rock with such a texture. CF: poikilitic. Syn: doleritic.

optical anomaly
 * Optical properties apparently at variance with optical rules, such as: anisotropy in isotropic minerals, such as birefringent diamond; biaxiality in uniaxial minerals, such as quartz; and erratic variation in birefringence near optical absorption bands--e.g., some epidote minerals.

optical calcite
 * Crystalline calcite so clear that it has value for optical purposes; e.g., polarizers. Syn: Iceland spar.

optical centering device
 * An optical device that enables a theodolite to be accurately positioned over or under a survey station. Also called optical plummet (undesirable usage).

optical character
 * The designation as to whether optically positive or optically negative; said of minerals.

optical constant
 * In optical mineralogy, any of the following: indices of refraction, birefringence, optic sign, axial angles, extinction angles, and dispersion of a nonopaque mineral. In ore microscopy (mineragraphy), any of the reflectances and anisotropy of opaque minerals. See also: reflected-light microscope.

optical crystallography
 * The study of the behavior of light in crystals.

optical diffraction
 * Constructive interference of monochromatic light; e.g., labradorescence in plagioclase, fire in opal. See also: diffraction.

optical flat
 * Glass or other surface rendered truly planar.

optical glass
 * Carefully made glass of great uniformity and usually special composition to give desired transmission, refraction, and dispersion of light.

optical mineralogy
 * The determination of optical properties of minerals for the purpose of characterization and identification. See also: index of refraction.

optical property
 * Any of several effects of a substance upon light. Refractive index, double refraction, (and its strength, birefringence), dispersion, pleochroism, and color are gemmologically the most important optical properties.

optical pyrometer
 * A type of pyrometer that measures high temperature by comparing the intensity of light of a particular wavelength from the hot material with that of a filament of known temperature. It is used to determine the temperature of incandescent lavas. See also: pyrometer.

optical sign
 * When a translucent crystal is viewed under microscope, light travels through the mineral at a speed which corresponds with its refractive index, as this is affected by the crystal planes. A uniaxial crystal has a negative optical sign when the velocity of its extraordinary ray exceeds that of the ordinary ray and vice versa. Calcite is negative; quartz positive. For biaxial crystals, the three principal directions of vibration are mutually at right angles.

optical square
 * A hand-held instrument enabling right angles to be set out accurately on a site.

optical twinning
 * A type of twinning in quartz in which the parts of the twin are alternately left- and right-handed. So named because it can be recognized by optical tests in distinction to Dauphine (electrical) twinning. Optical twinning as ordinarily applied includes all twin laws in quartz with the exception of the Dauphine. Also called Brazil twinning; chiral twinning.

optic angle
 * The angle between the two optic axes of a biaxial crystal; its symbol is 2V (less than 90 degrees ), 2V (sub alpha ), or 2V (sub gamma ) , depending on whether the optic direction X or Z is in the acute bisectrix. Syn: axial angle; optic-axial angle. CF: acute bisectrix; obtuse bisectrix.

optic-axial angle
 * See: optic angle.

optic axis
 * A direction of single refraction in a doubly refracting mineral. Hexagonal and tetragonal minerals have one such axis, and are termed uniaxial; rhombic, monoclinic, and triclinic minerals have two optic axes and are thus biaxial. See also: uniaxial; dispersion. CF: extinction.

optics
 * The sub-field of physics that covers the behavior of light.

optic sign
 * a. Indicates the type of double refraction in a mineral. In uniaxial minerals, the material is said to be positive when the extraordinary ray has a higher refractive index than the ordinary ray and negative when the ordinary ray has the greater index. In biaxial minerals, which have three basic optical directions, the refractive index of the intermediate or beta ray is the criterion; if its refractive index is nearer that of the low or alpha ray, it is said to be a positive mineral or stone; if it is nearer the high or gamma ray, it is said to be a negative mineral or stone.

b. More technically, in uniaxial minerals, the material is positive when the extreme refractive index (n (sub epsilon ) ) is greater than the apparently isotropic one (n (sub omega ) ) and negative when the extreme refractive index is less. In biaxial minerals, which have extreme refractive indices both above and below the apparently isotropic one (n (sub beta ) ), the material is positive when the lower refractive index (n (sub alpha ) ) is closer to the apparently isotropic one and negative when the higher one (n (sub gamma ) ) is closer. Syn: optical sign; optical character. See also: interference.

optimization
 * Coordination of various processing factors, controls, and specifications to provide best overall conditions for technical and/or economic operation.

optimum depth of cut
 * That depth of cut required to completely fill the dipper in one pass without undue crowding.

optimum moisture content
 * The water content at which a soil can be compacted to the maximum dry unit weight by a given compactive effort. Also called optimum water content.

option
 * a. A privilege secured by the payment of a certain consideration for the purchase, or lease, of mining or other property, within a specified time, or upon the fulfillment of certain conditions set forth in the contract.

b. S. Afr. The word option may refer to shares under option to the holder of option certificates. In regard to mining activities, options are granted to acquire the mineral rights and/or surface rights over some farm at a price fixed in the agreement. This price may be a sum of money or a participation in a mining company still to be formed. The option itself can be acquired for a lump sum or for a payment of so much per morgen a year. The option contract is generally connected with the permission for the option holder to prospect for minerals and briefly referred to as option and prospecting contract.

optional-flow storage
 * In coal preparation, optional-flow setups are those where coal usually goes to the plant but can be diverted into storage, either in bins or hoppers or on the ground.

opx
 * Abbrev. for orthopyroxene. CF: cpx.

oral agreement to locate
 * An agreement to locate need not be in writing. If a party, in pursuance of an oral agreement to locate at the expense of another, locates the claim in his or her own name, he or she holds the legal title to the ground in trust for the benefit of the party for whom the location was made. Such a party could, upon making the necessary proofs, compel the locator of the mining claim to convey the title to him or her, although the agreement to do so was not in writing. Such an agreement is not within the statute of frauds.

orange heat
 * A division of the color scale, generally given as about 900 degrees C.

orangepeel
 * A variant of the clamshell bucket with four or five leaves instead of the clamshell's two. Each leaf ends in a reinforced point. Its digging ability is less than that of the clamshell, and its principal use is for underwater excavation and digging.

orangepeel sampler
 * An apparatus consisting of four movable jaws that converge to a point when closed; used to obtain samples of underwater sediment.

orbicular
 * Adj. Describes rounded to spherical, commonly banded, textures within minerals or rocks; e.g., orbicular diorite.

orbicular structure
 * A structure developed in certain phanerocrystalline rocks (e.g., granite and diorite) due to the occurrence of numerous orbicules. Syn: spheroidal structure; nodular structure.

orcelite
 * A hexagonal mineral, Ni (sub 5-x) As (sub 2) ; rose-bronze; at the Tiebaghe massif, New Caledonia.

ordered solid solution
 * A condition when atoms in a solid solution arrange themselves in regular or preferential positions in the lattice, rather than at random.

order of crystallization
 * The apparent chronological sequence in which crystallization of the various minerals of an assemblage takes place, as evidenced mainly by textural features. See also: paragenesis.

order of persistence
 * See: stability series.

order of reaction
 * A classification of chemical reactions based on the index of the power to which concentration terms are raised in the expression for the instantaneous velocity of the reaction; i.e., on the apparent number of molecules which interact.

ordinary kriging
 * A variety of kriging which assumes that local means are not necessarily closely related to the population mean, and which therefore uses only the samples in the local neighborhood for the estimate. Ordinary kriging is the most commonly used method for environmental situations. See also: kriging.

ordinary ray
 * a. In a uniaxial crystal, that ray that travels with constant velocity in any direction within it.

b. In mineral optics, a light ray that, because of its crystallographic orientation, follows Snell's law, n=sini/sinr, where n is the refractive index, i is the angle of incidence, and r is the angle of refraction. In anisotropic crystals, not all light rays follow Snell's law and are, hence, "extraordinary rays." CF: law of refraction.

ordinate
 * Y-axis; the vertical scale of a graph.

ordnance bench mark
 * Survey station the level of which has been officially fixed with reference to the ordnance datum, the arbitrary mean sea level at Newlyn in Cornwall, England.

ordnance survey
 * Originally, a military mapping activity; now a precise survey maintained by government which maps land and building features of Great Britain in close detail.

ordonezite
 * A tetragonal mineral, ZnSb (sub 2) O (sub 6) ; brown.

ore
 * a. The naturally occurring material from which a mineral or minerals of economic value can be extracted profitably or to satisfy social or political objectives. The term is generally but not always used to refer to metalliferous material, and is often modified by the names of the valuable constituent; e.g., iron ore. See also: mineral; mineral deposit; ore mineral. Syn: orebody.

b. The term ores is sometimes applied collectively to opaque accessory minerals, such as ilmenite and magnetite, in igneous rocks.

ore band
 * Zone of rock rich in ore.

ore-bearing fluid
 * See: hydrothermal solution.

ore bed
 * a. Metal-rich layer in a sequence of sedimentary rocks.

b. Economic aggregation of minerals occurring between or in rocks of sedimentary origin.

ore bin
 * a. A receptacle for ore awaiting treatment or shipment.

b. Robustly constructed steel, wooden, or concrete structure which receives intermittent supplies of mined ore and can transfer them continuously by rate-controlled withdrawal systems (bottom gates and ore feeders) to the treatment plant. Thus a buffer stock is held which allows a mine to hoist ore intermittently without bringing milling operations to a standstill. It characteristically receives a weighed-in input of finely broken ore from the final dry-crushing section (usually between 1-in and 3/8-in (2.54-cm and 9.5-mm) maximum particle size). The surge bin is a much smaller one, able to receive a dumped load of run-of-mine ore and to transfer it at a regular rate to the crushing system between arrivals of further skip loads.

ore blending
 * Method whereby a mine, or a group of mines, served by a common mill, sends ores of slightly varied character for treatment and separate bins or stockpiles are provided. From these, regulated percentages of ores are drawn and blended to provide a steady and predictable feed to the mineral dressing plant.

ore block
 * A section of an orebody, usually rectangular, that is used for estimates of overall tonnage and quality. See also: blocking out.

ore blocked out
 * See: developed reserve.

ore boat
 * A boat constructed esp. for transporting iron ore on the Great Lakes.

orebody
 * A continuous, well-defined mass of material of sufficient ore content to make extraction economically feasible. See also: ore; mineral deposit.

ore boil
 * A reaction that occurs in an open-hearth furnace in which the carbon monoxide released by the oxidation of carbon causes a violent agitation of the metal as it escapes.

ore bridge
 * A large electric gantry-type crane which, by means of a clamshell bucket, stocks ore or carries it from a stockpile into bins or a larry car on a trestle.

ore-bridge bucket
 * A clamshell grab bucket of 5 to 7 tons capacity.

ore car
 * A mine car for carrying ore or waste rock.

ore chute
 * An inclined passage, from 3 to 4 ft (approx. 1 m) square, for the transfer of ore to a lower level, car, conveyor, etc. It may be constructed through waste fills. See also: orepass.

ore cluster
 * A genetically related group of orebodies that may have a common root or source rock but that may differ structurally or otherwise.

ore control
 * Any tectonic, lithologic, or geochemical features considered to have influenced the formation and localization of ore.

ore crusher
 * a. A machine for breaking up masses of ore, usually prior to passing through stamps or rolls. See also: crusher.

b. See: crusher man.

ore delfe
 * a. Ore lying underground.

b. Right or claim to ore from ownership of land in which it is found.

ore deposit
 * a. A body of ore. See also: mineral deposit.

b. A mineral deposit that has been tested and is known to be of sufficient size, grade, and accessibility to be producible to yield a profit. (In controlled economies and integrated industries, the "profit" decision may be based on considerations that extend far beyond the mine itself, in some instances relating to the overall health of a national economy.)

ore developed
 * See: positive ore.

ore developing
 * Ore exposed on two sides. First class, blocks with one side hidden; second class, blocks with two sides hidden; third class, blocks with three sides hidden. See also: probable ore.

ore dike
 * An injected wall-like intrusion of magmatic ore, forced in a liquid state across the bedding or other layered structure of the invaded formation.

ore district
 * A combination of several ore deposits into one common whole or system.

ore dressing
 * The cleaning of ore by the removal of certain valueless portions, such as by jigging, cobbing, vanning, etc. See also: concentration; beneficiation; preparation. Syn: mineral dressing; ore preparation.

ore expectant
 * The whole or any part of the ore below the lowest level or beyond the range of vision. The prospective value of a mine beyond or below the last visible ore, based on the fullest possible data from the mine being examined, and from the characteristics of the mining district. See also: possible ore; prospective ore.

ore face
 * An orebody that is exposed on one side, or shows only one face, and of which the values can be determined only in a prospective manner, as deducted from the general condition of the mine or prospect.

ore-forming fluid
 * A gas or fluid that dissolves, receives by fractionation, transports, and precipitates ore minerals. A mineralizer is typically aqueous, with various hyperfusible gases (CO (sub 2), CH (sub 4) , H (sub 2) S, HF), simple ions (H (super +) , HS, Cl (super -) , K, Na, Ca), complex ions (esp. chloride complexes), and dissolved base and precious metals. Syn: geologic mineralizer; mineralizer; hydrothermal solution.

ore genesis
 * The origin of ores.

ore geology
 * The branch of applied geology dealing with the genetic study of ore deposits. Syn: metallogeny; mining geology. See also: economic geology.

oregonite
 * Probably Ni (sub 2) FeAs (sub 2) ; hexagonal. From Josephine Creek, Josephine County, OR. Named from the locality. Also spelled oregonit.

ore grader
 * In metal mining, a person who directs and regulates the storage of iron ores of various grades in bins at shipping docks so that the grade of ore contained in each bin will contain the approximate percentage of iron guaranteed to the buyer (iron and steel mills).

ore guide
 * Any natural feature--such as alteration products, geochemical variations, local structures, or plant growth--known to be indicative of an orebody or mineral occurrence.

ore hearth
 * A small, low fireplace surrounded by three walls, with a tuyere at the back. Three important types are called: ore hearth, waterback ore hearth, and Moffet ore hearth; used in smelting.

oreing down
 * A blocking operation in which ore is added to an open-hearth bath to oxidize the bath and to further reduce the carbon.

ore in sight
 * a. A term frequently used to indicate two separate factors in an estimate, namely: (1) ore blocked out; i.e., ore exposed on at least three sides within reasonable distance of each other; and (2) ore that may be reasonably assumed to exist, though not actually blocked out; these two factors should in all cases be kept distinct, because (1) is governed by fixed rules, while (2) is dependent upon individual judgment and local experience. The expression ore in sight as commonly used in the past, appears to possess so indefinite a meaning as to discredit its use completely. The terms positive ore, probable ore, and possible ore are suggested.

b. See: developed reserve.

ore intersection
 * The point at which a borehole, crosscut, or other underground opening encounters an ore vein or deposit; also, the thickness of the ore-bearing deposit so traversed.

ore magma
 * A term proposed by Spurr (1923) for a magma that may crystallize into an ore; the sulfide, oxide, or other metallic facies of a solidified magma.

ore microscope
 * See: reflected-light microscope.

ore microscopy
 * The study of opaque ore minerals in polished section with a reflected-light microscope. See also: reflected-light microscopy; microscopy.

ore mineral
 * The part of an ore, usually metallic, which is economically desirable, as contrasted with the gangue. See also: ore. CF: gangue.

ore partly blocked
 * Said of an orebody that is only partly developed, and the values of which can be only approx. determined. See also: probable ore.

orepass
 * A vertical or inclined passage for the downward transfer of ore; equipped with gates or other appliances for controlling the flow. An orepass is driven in ore or country rock and connects a level with the hoisting shaft or with a lower level. See also: ore chute.

ore personal property
 * Ore, or other mineral product, becomes personal property when detached from the soil in which it is imbedded.

ore pipe
 * A long and relatively thin deposit commonly formed at the intersection of two planes. See also: pipe.

ore plot
 * A place where dressed ore is kept.

ore pocket
 * a. Excavation near a hoisting shaft into which ore from stopes is moved, preliminary to hoisting.

b. Used in a phrase such as a rich pocket of ore, to describe an unusual concentration in the lode.

ore preparation
 * See: ore dressing.

ore province
 * A well-defined area containing ore deposits of a particular kind; e.g., the porphyry copper deposits of the Southwestern United States. Related to, but not exactly synonymous with, metallogenic province, which need not contain economic ore deposits.

ore reserve
 * a. The term is usually restricted to ore of which the grade and tonnage have been established with reasonable assurance by drilling and other means.

b. The total tonnage and average value of proved ore, plus the total tonnage and value (assumed) of the probable ore. c. A mine's substantial asset, without which none of the surface works are economically viable. A body of ore that has been proved to contain a sufficient tonnage of amenable valuable mineral to justify the mining enterprise. The British Institution of Mining and Metallurgy, which regulates the professional standards of its membership, considers that the term ore reserves should be restricted to ore of which the quantity and grade have been established with reasonable assurance by a responsible, professionally qualified person. Additional ore insufficiently developed or tested for inclusion in ore reserves should be clearly described in simple terms best suited to the circumstances; modes of mineral occurrence vary too widely to permit standardization of categories. d. S. Afr. Orebodies made available for mining through drives connected by winzes (a connection driven down) and raises (a connection driven up), thus forming blocks that are accessible from four sides. Some companies record partially developed ore reserves in which this making of blocks has not been completed. Newcomers in gold mining occasionally speak of ore reserves when they mean the orebodies contained in a mining area and in copper mining this method of expression has been accepted by large concerns. e. See: reserve.

ore sampling
 * The process in which a portion (sample of ore) is selected in such a way, that its composition will represent the average composition of the entire bulk of ore. Such a selected portion is a sample, and the art of properly selecting such a sample is called sampling.

ore separator
 * A cradle, frame, jigging machine, washer, or other device or machine used in separating the metal from broken ore, or ore from worthless rock.

ore shoot
 * a. An elongate pipelike, ribbonlike, or chimneylike mass of ore within a deposit (usually a vein), representing the more valuable part of the deposit. Syn: shoot.

b. Concentration of primary ore along certain parts of a rock opening. c. A large and visually rich aggregation of mineral in a vein. It is a more or less vertical zone or chimney of rich vein matter extending from wall to wall, and has a definite width laterally. Sometimes called pay streak, although the latter applies more specif. to placers. d. An area of payable lode surrounded by low values. See also: shoot.

ore sill
 * A tabular sheet of magmatic ore, injected in a liquid state along the bedding planes of a sedimentary or other layered formation.

ore stamp
 * A machine for reducing ores by stamping.

ore-storage drier man
 * One who removes moisture from ore or other material preparatory to roasting or electrolytic processing, using a gas or hot-air drier. Also called drier operator.

ore strand
 * Individual mass of quartz with a halo of alteration and ore minerals, or close assemblage of seams of such quartz and accompanying altered ground.

ore trend
 * A term used on the Colorado Plateau to indicate the extension of an orebody along its major axis; the average trend of ore in a particular area, or the regional trend of mineralization over a large area. The local trend of individual orebodies may vary from the regional trend of so-called mineral belts.

ore vein
 * A tabular or sheetlike mass of ore minerals occupying a fissure or a set of fissures and later in formation than the enclosing rock.

ore washer
 * A machine for washing clay and earth out of earthy brown hematite ores. The log washer is a common type.

ore zone
 * A horizon in which ore minerals are known to occur.