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Appendix:Dictionary of Mining, Mineral, and Related Terms/B/2

bc-joint
 * See: longitudinal joint.

b direction
 * See: b axis.

beach concentrate
 * A natural accumulation in beach sand of heavy minerals selectively concentrated (by wave, current, or surf action) from the ordinary beach sands in which they were originally present as accessory minerals; esp. a beach placer. See also: beach placer.

beach deposit
 * Concentrations of mineral formed by the grinding action of natural forces (wind, wave, or frost) and the selective transporting action of tides and winds.

beach drift
 * The movement of material along the shore by the action of the uprush and backwash of waves breaking at an angle with the shore. Syn: longshore drift.

beach mining
 * The exploitation of the economic concentrations of the heavy minerals rutile, zircon, monazite, ilmenite, and sometimes gold, which occur in sand dunes, beaches, coastal plains, and deposits located inland from the shoreline. High-grade concentrate is usually obtained from low-grade material by the use of suction dredges and spiral concentrators.

beach ore
 * See: beach placer.

beach placer
 * A placer deposit on a present or ancient sea beach. There may be a series of paleo-beach placers owing to changes of shoreline. See also: black sand; placer; beach concentrate. Syn: beach ore.

beach ridge
 * A low, essentially continuous mound of beach or beach-and-dune material (sand, gravel, shingle) heaped up by the action of waves and currents on the backshore of a beach beyond the present limit of storm waves or the reach of ordinary tides, and occurring singly or as one of a series of approx. parallel deposits. The ridges are roughly parallel to the shoreline and represent successive positions of an advancing shoreline.

bead
 * a. The globule of precious metal obtained by the cupellation process in assaying.

b. In blowpipe analysis of minerals, a drop of a fused material, such as a "borax bead," used as a solvent in color testing for various metals. The addition of a metallic compound to the bead will cause the bead to assume the color that is characteristic of the metal. See also: blowpiping.

beads
 * In ion exchange, sized resin spheres, usually +20 mesh, so constituted as to capture ions from pregnant solutions under stated loading conditions and to relinquish them under other (eluting) conditions. Two types are anionic and cationic. See also: resin.

bead tests
 * In mineral identification, borax or other flux is fused to a transparent bead by heating in a blowpipe or other flame in a small loop formed from platinum wire. When suitable minerals are flux melted in this bead, characteristic glassy colors are produced in an oxidizing or reducing flame and serve to identify specific chemical elements.

beaker decantation
 * A method of sizing finely ground, insoluble, homogeneous material or classifying ore particles. A weighed quantity is dispersed in liquid and allowed to settle for a timed period, a liquid fraction then being decanted. The treatment is repeated several times, the settled fraction now representing one size group (if homogeneous) or settled group (if minerals of various densities are present). The decanted fluid is similarly treated for progressively lengthened settling periods.

beam
 * a. A bar or straight girder used to support a span of roof between two support props or walls. See also: crossbar.

b. The walking beam; a bar pivoted in the center, which rocks up and down, actuating the tools in cable-tool drilling or the pumping rods in a well being pumped.

beam action
 * In crushing, seizure of rock slab between approaching jaws so as to present crushing stress above unsupported parts of the rock, thus inducing shear failure rather than failure under compression.

Beaman stadia arc
 * A specially graduated arc attached to the vertical circle of an alidade or transit to simplify the computation of elevation differences for inclined stadia sights (without the use of vertical angles). The arc is so graduated that each division on the arc is equal to 100 (0.5 sin 2A), where A is the vertical angle. Named after William M. Beaman (1867-1937), U.S. topographic engineer, who designed it in 1904.

beam building
 * A process of rock bolting in flat-lying deposits where the bolts are installed in bedded rock to bind the strata together to act as a single beam capable of supporting itself and thus stabilizing the overlying rock.

beam compass
 * An instrument for describing large arcs. It consists of a beam of wood or metal carrying two beam heads, adjustable for position along the beam, and serving as the marking points of the compass. Syn: trammel.

beam engine
 * An early type of vertical steam engine. It operated the Cornish pump.

bean ore
 * A loose, coarse-grained pisolitic iron ore; limonite occurring in lenticular aggregations. See also: pea ore.

bean rock
 * Shingle cemented by tufa, Ventnor, U.K.

beans
 * A cleaned and screened anthracite product 7/8 in by 3/8 in (22.2 mm by 9.5 mm).

bear
 * a. To bear in; underholing or undermining; driving in at the top or at the side of a working.

b. Eng. A calcareous or clay ironstone nodule, Derbyshire. c. The mass of iron, which, as a result of wear of the refractory brickwork or blocks in the hearth bottom of a blast furnace, slowly replaces much of the refractory material in this location. Syn: salamander.

bearer
 * Eng. A band of hard limestone consisting of numerous stromatoporoids, mainly a ramose species, Wenlock Limestone, Dudley.

bearer bar
 * One of the bars that support the grate bars in a furnace.

bearers
 * Heavy timbers placed in a shaft at intervals of 30 to 100 ft (9.1 to 30.5 m) to support shaft sets. They are usually put beneath the end plates and dividers, and rest in hitches cut in the wall. Also used to support pumping gear. Syn: biard.

bearing
 * a. The part of a beam or girder that actually rests on the supports.

b. Undercutting the coal face by holing. c. The horizontal angle between the meridian (true or magnetic) and any specified direction. The angle is measured from either the north or the south point, as may be required to give a reading of less than 90 degrees, and the proper quadrant is designated by the letter N or S, preceding the angle, and the letter E or W, following it; as, N. 80 degrees E. CF: azimuth. d. The points of support of a beam, shaft, or axle, i.e., bearing points. e. The direction of a mine drivage usually given in terms of the horizontal angle turned off a datum direction, such as the true north and south line. f. In Texas land surveys, a reference point to identify a land corner or a point on a survey line. g. A part in which a shaft or pivot revolves. h. See: ball bearing.

bearing bed
 * A bed that contains, or is likely to contain, ore minerals; one that is productive as opposed to dead or barren.

bearing capacity
 * a. The load-per-unit area that the soil or solid rock can support without excessive yield. See also: foundation investigation.

b. See also: ultimate bearing capacity.

bearing door
 * A door so placed as to direct and regulate the amount of air current necessary for the proper ventilation of a district of a mine. See also: separation door.

bearing-in
 * The depth of an undercut, or holing, from the face of the coal to the end of the undercut.

bearing-in shots
 * Boreholes tending to meet in the body of the rock; intended to unkey the face when charged and fired.

bearing plate
 * A plate of the thickness and area required to distribute a given load, such as a plate under a beam flange resting on a wall. If the plate is 2 in (5.1 cm) or more in thickness, it is called a slab.

bearing pressure
 * The load on a bearing surface divided by the area upon which it rests.

bearing set
 * In a mine shaft, a specially substantial set of timbers used at intervals to support the linings and ordinary bearers. They are tied into the surrounding rock to give extra strength.

bearing stake
 * A stake set on a line to indicate the horizontal direction an inclined borehole is to be drilled.

bearing stratum
 * The earth formation that has been selected as the most suitable to support a given load.

bearing strength
 * The maximum bearing load at failure divided by the effective bearing area. In a pinned or riveted joint, the effective area is calculated as the product of the diameter of the hole and the thickness of the bearing member.

bearsite
 * A monoclinic mineral, Be (sub 2) (AsO (sub 4) )(OH).4H (sub 2) O.

bears' muck
 * Eng. Soft, bluish earth. Used by well sinkers in Cambridgeshire and Huntingdonshire. See also: caballa ball.

beater
 * A laborer who shovels or dumps asbestos fibers and sprays them with water to prepare them for the beating process that reduces fibers to pulp for making asbestos paper.

beater mill
 * Mill used for impact crushing of easily broken minerals. An armature carrying swinging hammers, plates, or disks hits the falling stream of rock, dashing particles against one another and against the casing of the mill. See: hammermill.

beaverite
 * A trigonal mineral, Pb(Cu,Fe,Al) (sub 3) (SO (sub 4) ) (sub 2) (OH) (sub 6) ; canary yellow; in minute plates; in Beaver County, UT.

Becke line
 * In the "Becke test" a bright line, visible under a microscope under plane polarized light, that separates substances of different indices of refraction.

beckerite
 * a. A brown resin, occurring with amber.

b. A brown variety of retinite having a very high oxygen content (20% to 23%).

Becke test
 * In polarized-light microscopy, a method or test for determining relative indices of refraction between two adjacent mineral grains or between a mineral grain and its host medium; e.g., Canada balsam, Lakeside cement, an epoxy resin, or an immersion oil of known index of refraction. On defocusing by increasing the working distance between the microscope stage and the objective lens, the Becke line moves toward the higher index of refraction. CF: van der Kolk method.

Becorit system
 * An overhead monorail system. See also: monorail.

becquerelite
 * An orthorhombic mineral, Ca(UO (sub 2) ) (sub 6) O (sub 4) (OH) (sub 6) .8H (sub 2) O, with barium and potassium substitution for calcium; amber-yellow; a radioactive product of uraninite and ianthinite alteration.

bed
 * a. The smallest distinctive division of a stratified series, marked by a more or less well-defined surface or plane from its neighbors above and below; a layer or stratum.

b. A deposit, as of ore, parallel to the stratification. c. A bed (or beds) is the smallest formal lithostratigraphic unit of sedimentary rocks. The designation of a bed or a unit of beds as a formally named lithostratigraphic unit generally should be limited to certain distinctive beds whose recognition is particularly useful. Coalbeds, oil sands, and other beds of economic importance commonly are named, but such units and their names usually are not a part of formal stratigraphic nomenclature (NACSN, 1983, Art. 26). d. That portion of an outcrop or face of a quarry that occurs between two bedding planes. e. The level surface of rock upon which a curb or crib is laid. f. All the coal, partings, and seams that lie between a distinct roof and floor. g. Perhaps the most common term in geology, meaning layer or stratum. Quarrymen usually mean by beds not the stone beds in the geologist's sense but the partings between them. h. A stockpile, as of ore, concentrates, and fluxes, built up of successive layers so that transverse cutting yields a uniform mixture for furnace feed until the material is all consumed. i. In mineral processing, a heavy layer of selected oversized mineral or metal shot maintained on screen of jig. j. That part of conveyor upon which the load or carrying medium rests or slides while being conveyed. k. In bulk material conveyors, the mass of material being conveyed. l. A base for machinery.

bed claim
 * Aust. A mining claim lying on the bed of a stream.

bedded
 * Applied to rocks resulting from consolidated sediments and accordingly exhibiting planes of separation designated bedding planes.

bedded deposit
 * a. A term usually applied to mineral deposits that are found parallel with the stratification of sedimentary rocks and usually of contemporaneous origin. The term is used to describe layerlike deposits of replacement origin. See also: bedded formation.

b. Syn: blanket deposit.

bedded formation
 * A formation that shows successive beds, layers, or strata owing to the manner in which it was formed. See also: bedded deposit.

bedded rock
 * One of the two subdivisions of competent rock. To be classed as bedded rock, the rock within each bed, in addition to being elastically perfect, isotropic, and homogeneous, must have a bed thickness that is small compared with the roof span, and the bond between beds must be weak. Most sedimentary rocks and some stratified metamorphic rocks fall in this group.

bedding
 * a. A quarry term for a structure occurring in granite and other crystalline rocks that tend to split in well-defined planes more or less horizontal or parallel to the land surface. Syn: sheeting.

b. The storing and mixing of different ores in thin layers in order to blend them more uniformly in reclamation. c. The layer of heavy and oversized material placed above the screen in jigging. Also called ragging. d. Pieces of soft metal placed under or around a handset diamond as a cushion or filler. Also called backing; calking. e. Ground or supports in which pipe is laid. f. The arrangement of a sedimentary rock in beds or layers of varying thickness and character; the general physical and structural character or pattern of the beds and their contacts within a rock mass, such as cross-bedding and graded bedding; a collective term denoting the existence of beds. Also, the structure so produced. The term may be applied to the layered arrangement and structure of an igneous or metamorphic rock. See also: stratification. Syn: layering. CF: bedding plane. g. The initial filling of a thickener for continuous operation.

bedding cleavage
 * Cleavage that is parallel to the bedding.

bedding down
 * Formation of layer of valueless and inert rock at points in a new flowline where material will settle from the stream of ore being treated, for example, between bottom of thickener and its rakes.

bedding fault
 * A fault that is parallel to the bedding.

bedding fissility
 * A term generally restricted to primary foliation parallel to the bedding of sedimentary rocks; i.e., it forms while the sediment is being deposited and compacted. It is the result of the parallelism of the platy materials to the bedding plane, partly because they were deposited that way and partly because they were rotated into this position during compaction.

bedding glide
 * Overthrusting in which a bed, such as a coal seam, is disrupted and thrust laterally along the roof or floor parting, giving a duplication of coal.

bedding joint
 * a. A thin layer differing in composition with the beds between which it occurs.

b. A joint parallel to the bedding planes formed by tectonic processes.

bedding plane
 * a. In sedimentary or stratified rocks, a surface that separates each layer from those above or below it. It usually records a change in depositional circumstances by grain size, composition, color, or other features. The rock may tend to split or break readily along bedding planes. See also: plane.

b. Surface on which rock-forming mineral has been deposited. Syn: bedding. c. A separation or weakness between two layers of rock caused by changes during the building up of the rock-forming material. See also: bed joint.

bedding thrust
 * A thrust fault that is parallel to the bedding.

bede
 * A miner's pick.

Bedford limestone
 * One of the finest and best known building stones to be found in the United States. It gets its name from its shipping point, Bedford, IN.

bed joint
 * a. A horizontal crack or fissure in massive rock. See also: bedding plane.

b. One of a set of cracks or fissures parallel with the bedding of a rock. c. A horizontal joint between courses of brick. d. The horizontal layer of mortar on (or in) which a masonry unit is laid.

bedrock
 * a. Solid rock exposed at the surface of the Earth or overlain by unconsolidated material, weathered rock, or soil.

b. In Australia, the stratum upon which the wash dirt rests is usually called bedrock. It usually consists of granite or boulder clay (glacial) and, much more rarely, basalt. When the stratum consists of slates or sandstones (Silurian or Ordovician), it is usually called reef rock. c. A general term for the rock, usually solid, that underlies soil or other unconsolidated, superficial material. A British syn. of the adjectival form is "solid," as in solid geology. See: stonehead. d. See: bottom rock; rock base.

bedrock test
 * A borehole drilled to determine the character of bedrock and the character and depth of overburden overlying such bedrock. Syn: testing bedrock.

bed separation
 * The thin cavities formed along bedding planes due to differential lowering of strata over mine workings; e.g., a shale with its greater bending capacity will subside and separate from a higher bed of sandstone. Roof supports are so set as to keep bed separation to a minimum.

bed vein
 * A vein following the bedding in sedimentary rocks, or a mineralized permeable stratigraphic zone below an impervious bed. CF: blanket vein; manto; sheet ground.

beech coal
 * Charcoal made from beechwood.

beeches
 * Scot. Strips of hardwood fastened to pump rods to save them from wear at the collars.

beef
 * A quarry worker's term, used originally in Purbeck, southern England, for thin, flat-lying veins or layers of fibrous calcite, anhydrite, gypsum, halite, or silica, occurring along bedding planes of shale, giving a resemblance to beef. It appears to be due to rapid crystallization in lenticular cavities. See also: bacon.

beehive coke
 * Coke manufactured in beehive, rectangular, or similar forms of ovens in a horizontal bed, where heat for the coking process is secured by combustion within the oven chamber.

beehive coke oven
 * A coke oven with a brick bottom, side walls, and a domed roof.

beehive kiln
 * An intermittent kiln, circular in plan, with fireboxes arranged around the circumference. Such kilns find use in the firing of blue engineering bricks, pipes, some refractory bricks, etc. Syn: round kiln.

Beethoven exploder
 * A machine for the multishot firing of series-connected detonators in tunneling and quarrying. See also: exploder.

beetle stone
 * A nodule of coprolitic ironstone, so named from the resemblance of the enclosed coprolite to the body and limbs of a beetle. Syn: septarium.

beetling stones
 * Flat rocks on which clothes were beetled (stamped or pounded).

before breast
 * A miner's term for that part of the orebody that still lies ahead. See also: breast.

beidellite
 * A monoclinic mineral, (Na,Ca (sub 0.5) ) (sub 0.3) Al (sub 2) (Si,Al) (sub 4) O (sub 10) (OH) (sub 2) .nH (sub 2) O ; smectite group; aluminum rich and poor in magnesium and iron; a common constituent of soils and certain clay deposits (e.g., metabentonite). CF: montmorillonite.

Beien kep gear
 * An improved type of kep in which the kep shoes are withdrawn without previously raising the cage and thus reducing the decking time. The operation may be automatic, except for cage release, because the arrangement allows the kep shoes to trip without the position of the hand lever being altered. See also: kep.

Beien machine
 * A pneumatic stowing machine that consists of a paddle wheel with six compartments working inside an adjustable airtight casing. This wheel is driven at a speed of 15 to 30 rpm by means of an air turbine through gearing. Two sizes of Beien machines are used having capacities of 30 yd (super 3) and 60 yd (super 3) (22.9 m (super 3) and 45.9 m (super 3) ) of stowing material per hour, respectively. The dirt falls from the paddle wheel into the airstream in the pipe underneath the paddle box and passes along 6-in (15.2-cm) diameter pipes to the outlet, where a detachable deflector guides the stream of dirt into the required place in the pack hole.

Beilby layer
 * Flow layer resulting from incipient fusion during polishing of mineral surface, and therefore not characteristic of true crystal structure.

Belfast truss
 * A bowstring design of girder fabricated entirely from timber components.

Belgian coke oven
 * A rectangular variation of the beehive coke oven. See also: Belgian oven.

Belgian effective temperature
 * A temperature scale used in Belgium for measuring the environmental comfort in mines.

Belgian oven
 * A rectangular oven with end doors and side flues for the manufacture of coke. See also: Belgian coke oven.

Belgian press
 * See: double-roll press.

Belgian process
 * A process (no longer used) to smelt zinc in which roasted zinc ore is mixed with a reducing material, such as coal or coke, placed in cylindrical retorts, and heated in a furnace, such that the escaping zinc vapor is condensed from the open end of the retort.

Belgian silex
 * A very hard, tough, more or less cellular quartzite resembling French buhrstone and the most favored natural mill-lining material for most purposes. It is imported in rectangular blocks that are more or less shaped to fit the curve of a mill.

Belgian zinc furnace
 * A furnace in which zinc is reduced and distilled from calcined ores in tubular retorts. These furnaces may be classified as direct fired and gas fired, but there is no sharp division between these systems, which merge into one another by difficultly definable gradations. Each class of furnace may be subdivided into recuperative and nonrecuperative, but heat recuperation in connection with direct firing is rare.

belgite
 * See: willemite.

belite
 * a. A constituent of portland cement clinkers.

b. A calcium orthosilicate found as a constituent of portland-cement clinkers; specif. larnite. Syn: felite.

belith
 * Original spelling of belite.

Belknap chloride washer process
 * This coal washer uses a calcium chloride solution of a comparatively low density and depends on mechanically induced upward currents to obtain a separation at the desired specific gravity. It produces a clean, dustless, nonfreezing coal.

bell
 * a. A cone-shaped mass of ironstone or other substance in the roof of a coal seam. Bells are dangerous as they tend to collapse suddenly and without warning. See also: pot bottom.

b. A gong used as a signal at mine shafts. c. See: cone.

bellan
 * a. Eng. Dusty lead ore.

b. A form of lead poisoning to which miners are subject. Also spelled belland; bellund.

belland
 * See: bellan.

bell and hopper
 * See: cup and cone.

bellcrank drive
 * A device used to drive an auxiliary shaker conveyor without changing the direction of the main conveyor. It consists essentially of two driving arms, placed at right angles to each other and supported at their pivot point by a fulcrum jack. When these driving arms are attached to the main and auxiliary conveyors, the reciprocating motion of the main conveyor is transmitted to the auxiliary conveyor, which can then discharge its load onto the main conveyor.

belled
 * Eng. Widened; said of the enlarged portion of a shaft at the landing for running the cars past the shaft, and for caging.

bell holes
 * A conical cavity in a coal mine roof caused by the falling of a large concretion; or, as of a bell mold.

bellies
 * Widenings in a vein. See also: belly.

bellingerite
 * A triclinic mineral, Cu (sub 2) (IO (sub 3) ) (sub 6) .2H (sub 2) O ; forms light green or bluish green crystals; at Chuquicamata, Chile.

bellite
 * a. An explosive consisting of five parts of ammonium nitrate to one of metadinitrobenzene, usually with some potassium nitrate.

b. A lead chromo-arsenate in delicate velvety, red to orange tufts.

bell jar
 * See: jar collar.

bell-metal ore
 * Corn. An early name for tin pyrite (stannite), so called because of its bronze color. See also: stannite.

bell mold
 * Som. A conical-shaped patch of a mine roof, probably originating with the fossils called sigillaria, or the roots of trees. Syn: caldron. See also: bell; caldron bottom.

bellows
 * a. An instrument with an air chamber and flexible sides used for compressing and/or directing a current of air.

b. An expansible metal device containing a fluid that will volatilize at some desired temperature, expand the device, and open or close an opening or a switch; used in controls and steam traps.

bell pit mining
 * Obsolete method of winning coal or bedded iron from shallow deposits, in which mineral was extracted and dragged to a central shaft.

Bell process
 * See: Bell's dephosphorizing process.

bell screw
 * An internally threaded bell-shaped iron bar for recovering broken or lost rods in a deep borehole. Syn: box bell; screw bell; bell tap.

Bell's dephosphorizing process
 * The removal of phosphorus from molten pig iron in a puddling furnace lined with iron oxide and fitted with a mechanical rabble to agitate the bath. Red-hot iron ore is added. See also: Krupp washing process. Syn: Bell process.

bell sheave
 * Aust. A sheave in the shape of a truncated cone used in connection with the main-and-tail system of rope haulage at curves, so as to keep the rope close to the ground.

bell socket
 * See: bell tap; screw bell.

bell tap
 * A cylindrical fishing tool having an upward-tapered inside surface provided with hardened threads. When slipped over the upper end of lost, cylindrical, downhole drilling equipment and turned, the threaded inside surface of the bell tap cuts into and grips the outside surface of the lost equipment. Also called bell; box bill; die; die collar; die nipple. See also: bell screw; screw bell; die. Syn: bell socket; outside tap.

bell top
 * Term used to describe a good roof that has a clear ringing sound.

bellund
 * See: bellan.

bell work
 * a. Derb. A system of working an ironstone measure by upward underground excavations around the shafts (raises) in the form of a bell or cone.

b. A method used in working salt deposits.

belly
 * a. See: pocket.

b. A bulge, or mass of ore in a lode. c. Widened places in a borehole caused by sloughing of loose material from the borehole sidewalls. See also: bellies.

belly pipe
 * A flaring-mouthed blast pipe in an iron furnace.

Belomorite
 * Trade name for moonstone from the White Sea.

belonesite
 * A white, transparent magnesium molybdate, MgMoO (sub 4), crystallizing in the tetragonal system.

belonite
 * An elongated or acicular crystallite having rounded or pointed ends.

belovite
 * A hexagonal mineral, (Sr,Ce,Na,Ca) (sub 5) (PO (sub 4) ) (sub 3) (OH) ; apatite group; occurs in pegmatites.

belt
 * a. See: link-plate belt.

b. Can. Regional surface zone along which mines and prospects occur. c. A continuous strap or band for transmitting power from one wheel to another, or (rarely) to a shaft, by friction. See also: stitched canvas conveyor belt. d. A zone or band of a particular kind of rock strata exposed on the surface. CF: zone. e. An elongated area of mineralization.

belt capacity
 * The load that a belt conveyor is able to carry, depending upon the area of cross section of load on belt and the speed of the belt.

belt cleaner
 * A device attached to a belt conveyor to clean or remove dirt or coal dust from the belt surface. Rotary bristle brushes are sometimes used, driven either by gearing from the conveyor or by an independent high-speed motor. Another device consists of a short scraper conveyor with rubber-faced scrapers attached at intervals. The scraper belt is driven via a chain drive from the main conveyor drum.

belt conveyor
 * a. A moving endless belt that rides on rollers and on which materials can be carried. The principal parts of a belt conveyor are (1) a belt to carry the load and transmit the pull, (2) a driving unit, (3) a supporting structure and idler rollers between the terminal drums, and (4) accessories, which include devices for maintaining belt tension and loading and unloading the belt, and equipment for cleaning and protecting the belt. See also: hatch conveyor; underground mine conveyor.

b. See: troughed belt conveyor.

belt conveyor structure
 * The framework for supporting the bottom strand of a belt conveyor.

belt creep
 * Gentle slip.

belt dressing
 * A compound used to improve adhesion or flexibility.

belt feeder
 * Short loop of conveyor belt, or articulated steelplate, used to draw ore at a regulated rate from under a bin or stockpile.

belt flotation
 * A method sometimes used to recover diamond particles 1 mm or smaller.

belt friction
 * See: friction.

belt horsepower
 * That power developed with all auxiliary equipment (such as pump and fans) attached; it is consequently lower than flywheel horsepower.

belting
 * One of the main parts of a belt conveyor. The belting consists of piles of cotton duck impregnated with rubber, with top and bottom covers of rubber. The carrying capacity of the belt will vary, depending on the running speed and the width of the belt.

belt loader
 * A machine whose forward motion cuts soil with a plowshare or disk and pushes it to a conveyor belt that elevates it to a dumping point. Syn: elevating grader.

beltman
 * See: conveyor man.

belt of variables
 * The belt of marine deposition extending from the coast (high watermark) to a depth of about 100 fathoms (183 m); i.e., corresponding roughly with the continental shelf (in the wide sense, to include the shore); passing into the mud belt at the inner mud line.

belt press
 * A device for dewatering mineral slurries, esp. waste from coal washing, which consists of a moving belt constructed of relatively open cloth. Belt presses are widely used in the minerals industry.

belt protection device
 * A device fitted to a belt conveyor to give an alarm or to cause the conveyor to stop in the event of a defect, such as belt slip, breakage, tearing, misalignment, or overload.

belt slip
 * The difference in speed between the driving drum and the belt conveyor.

belt table
 * A table incorporating a belt conveyor so arranged as to provide working space on one or both sides of the belt.

belt tensioning device
 * A device fitted to a belt conveyor that automatically takes up any slack or stretch in the belting. A gravity takeup device is sometimes fitted immediately behind the driving unit, thus eliminating slack that would otherwise occur. The main disadvantage of gravity takeup is that it gives the belt three entire bends.

belt tripper
 * A device or mechanism that causes the conveyor belt to pass around pulleys for the purpose of discharging material from it.

belt-type conveyor
 * A conveyor consisting of an endless belt used to transport material from one place to another.

Belugou imperfection coefficient
 * In coal testing, a parameter, B, applied to the ash curve: B = (p75 - p25)/2(p50 - 1), where pX is the specific gravity of particles of which the fraction separated is X percent, (p75 - p25) is the statistical intermediate or inquartile range, and p50 is the effective density of separation in a process in which a dense medium, vertical current, or jigging action is used. Equation is used to define shape of a Tromp curve.

belyankinite
 * A mineral, Ca (sub 1-2) (Ti,Zr,Nb) (sub 5) O (sub 12) .9H (sub 2) O(?) ; amorphous, yellowish-brown.

Belynski's reagent
 * A 1% copper sulfate solution recommended as an etchant for revealing dendritic structures in high-carbon steels.

bementite
 * a. A light gray or grayish-brown, common manganese mineral, Mn (super 2+) (sub 8) Si (sub 6) O (sub 15) (OH) (sub 10).

b. An erroneous name for danburite.

ben
 * a. Scot. Inward; toward the workings; the workman's right to enter the pit.

b. The live or productive part of a lode. c. A mountain peak; a word occurring chiefly in the names of many of the highest summits of the mountains of Scotland, as Ben Nevis.

bench
 * a. A terrace on the side of a river or lake having at one time formed its bank. See also: bench gravel.

b. In an underground mine, a long horizontal face or ledge of ore in a stope or working place. c. A layer of coal; either a coal seam separated from nearby seams by an intervening noncoaly bed, or one of several layers within a coal seam that may be mined separately from the others. d. One of two or more divisions of a coal seam, separated by slate, etc., or simply separated by the process of cutting the coal, one bench or layer being cut before the adjacent one. e. The horizontal step or floor along which coal, ore, stone, or overburden is worked or quarried. See also: benching; opencast. f. A stratum of coal forming a portion of the seam; also, a flat place on a hillside indicating the outcrop of a coal seam. g. In tunnel excavation, where a top heading is driven, the bench is the mass of rock left, extending from about the spring line to the bottom of the tunnel. h. A part of the face of a large excavation that is advanced not as part of the round but as a separate operation. i. A ledge that, in open-pit mine and quarries, forms a single level of operation above which minerals or waste materials are excavated from a contiguous bank or bench face. The mineral or waste is removed in successive layers, each of which is a bench, several of which may be in operation simultaneously in different parts of, and at different elevations in, an open-pit mine or quarry. CF: berm. j. See: siege.

bench-and-bench
 * Ark. That plan of mining coal in a room that requires the blasting of the two benches of coal alternately, each a little beyond the other. Syn: bench working.

bench blasting
 * A mining system used either underground or in surface pits whereby a thick ore or waste zone is removed by blasting a series of successive horizontal layers called benches.

bench claim
 * A placer claim located on a bench above the present level of a stream.

bench coal
 * A coal seam cut in benches or layers.

bench cut
 * a. In vertical shaft sinking, blasting of drill holes so as to keep one end of a rectangular opening deep (leading), thus facilitating drainage and removal of blasted rock.

b. Benches in tunnel driving are often drilled from the top with jackhammers. The vertical shotholes are generally spaced 4 ft (1.2 m) apart in both directions, fired by electric delay detonators, one row at a time. When bench shotholes are drilled horizontally with the drifter drills mounted on a bar, the charges are fired in rotation, starting from the upper center. In some cases, a bench may be drilled both vertically and horizontally, particularly where the benches are exceptionally high or when the headroom above the bench is inadequate for handling drill steels long enough to bottom the shotholes to grade. The lifters are drilled by machines mounted on a bar across the bottom of the tunnel, in which case the upper vertical holes will all be fired before the horizontal charges.

bench diggings
 * River placers not subject to overflows.

benched foundation
 * Foundation excavated on a sloping stratum of rock, which is cut in steps so that it cannot slide when under load. Syn: stepped foundation.

benches
 * A name applied to ledges of all kinds of rock that are shaped like steps or terraces. They may be developed either naturally in the ordinary processes of land degradation, faulting, and the like; or by artificial excavation in mines and quarries.

bench face
 * See: bank.

bench flume
 * A conduit on a bench, cut on sloping ground.

bench gravel
 * A term applied in Alaska and the Yukon Territory to gravel beds on the side of a valley above the present stream bottom, which represent part of the stream bed when it was at a higher level. See also: bench; bench placer.

bench height
 * The vertical distance from the top of a bench to the floor or to the top of the next lower bench.

benching
 * a. A method of working small quarries or opencast pits in steps or benches, in which rows of blasting holes are drilled parallel to the free face. The benching method has certain dangers since the quarrymen must work on ledges at some height. It is possible to work benches up to 30 ft (9.1 m) high using tripod or wagon drills. See also: bottom benching; top benching.

b. The breaking up of a bottom layer of coal with steel wedges in cases where holing is done above the floor. c. Ches. The lower portion of the rock salt bed worked in one operation. d. See: bench.

benching iron
 * An item of surveying equipment, comprising a triangular steel plate with pointed studs at the corners. These studs are driven into the ground in the desired position. The plate is used either as a temporary bench mark or as a change point in running a line of levels.

bench mark
 * a. A relatively permanent metal tablet or other mark firmly embedded in a fixed and enduring natural or artificial object, indicating a precisely determined elevation above or below a standard datum (usually sea level); it bears identifying information and is used as a reference in topographic surveys and tidal observations. It is often an embossed and stamped disk of bronze or aluminum alloy, about 3.75 in (9.5 cm) in diameter, with an attached shank about 3 in (7.6 cm) in length, and may be cemented in natural bedrock, in a massive concrete post set flush with the ground, or in the masonry of a substantial building. Abbrev: BM.

b. A well-defined, permanently fixed point in space, used as a reference from which measurements of any sort (such as of elevation) may be made.

bench of timbers
 * A term used to describe the header when it is complete with legs. Syn: set.

bench placer
 * A bench gravel that is mined as a placer. Syn: bench gravel; river-bar placer; terrace placer.

bench scrap
 * The scrap mica resulting from rifting and trimming hand-cobbed mica.

bench slope
 * See: bank slope.

bench working
 * The system of working one or more seams or beds of mineral by open working or stripping in stages or steps. Syn: bench-and-bench.

benchy
 * Forming frequent benches; said of a lode.

Bendelari jig
 * A jig fitted with a flexible rubber diaphragm that is worked by an eccentric motion, thus producing a jigging cycle (pulsion suction). See also: jig.

bending stress
 * The stress produced in the outer fibers of a rope by bending over a sheave or drum.

bend pulley
 * An idler pulley that is used solely for the purpose of changing the direction of travel of the belt other than at the terminals of the conveyor.

bend radius
 * The inside radius of a bent section.

bends
 * Caisson disease, brought on by too sudden return to normal pressure after working in a pressurized shaft or tunnel.

bend shaft
 * A shaft that supports a bend wheel or pulley.

bend tangent
 * A tangent point where a bending arc ceases or changes.

bend test
 * A test for determining relative ductility of metal that is to be formed, usually sheet, strip, plate, or wire, and for determining soundness and toughness of metal. The specimen is usually bent over a specified diameter through a specified angle for a specified number of cycles.

bend wheel
 * A wheel used to interrupt and change the normal path of travel of the conveying or driving medium. Most generally used to effect a change in direction of conveyor travel from inclined to horizontal or a similar change.

beneficiate
 * To improve the grade by removing associated impurities; to upgrade.

beneficiation
 * a. The dressing or processing of coal or ores for the purpose of (1) regulating the size of a desired product, (2) removing unwanted constituents, and (3) improving the quality, purity, or assay grade of a desired product.

b. Concentration or other preparation of coal or ores for smelting by drying, flotation, or magnetic separation. c. Improvement of the grade of coal or ores by milling, flotation, sintering, gravity concentration, or other processes.

Bengal amethyst
 * An archaic trade name for purple sapphire.

benitoite
 * A hexagonal mineral, 2[BaTiSi (sub 3) O (sub 9) ] ; occurs in double pyramids; colorless, white, or blue, resembling sapphire; in veins in serpentine schist.

benjaminite
 * A monoclinic mineral, (Ag,Cu) (sub 3) (Bi,Pb) (sub 7) S (sub 12).

benstonite
 * A trigonal mineral, (Ba,Sr) (sub 6) (Ca,Mn) (sub 6) Mg(CO (sub 3) ) (sub 13) ; shows flat, simple rhombohedral crystals and cleavage; fluoresces yellow or red; in veins with calcite.

bent
 * a. In tunnel timbering, two posts and a roof timber.

b. A transverse structure consisting of legs, bracing, and feet used for the purpose of supporting a gallery or conveyor frame at a fixed elevation.

Benthic Division
 * A primary division of the sea that includes all of the ocean floor. The Benthic Division is subdivided into the Littoral System (the ocean floor lying in water depths ranging from the high watermark to a depth of 200 m or the edge of the continental shelf), and the Deep-Sea System (ocean floor lying in water deeper than 200 m). The systems are further subdivided into the Eulittoral Zone (0 to 50 m), Sublittoral Zone (50 to 200 m), Archibenthic Zone (200 to 1,000 m), and the Abyssal-Benthic Zone (1,000 m and greater).

benthonic
 * a. Refers to the bottom of a body of standing water.

b. Pertaining to benthos; also, said of that environment. Syn: demersal.

benthos
 * All plants and animals living on the ocean bottom.

bentonite
 * A montmorillonite-type clay formed by the alteration of volcanic ash. It varies in composition and is usually highly colloidal and plastic. Swelling bentonite is so named because of its capacity to absorb large amounts of water accompanied by an enormous increase in volume. Occurs in thin deposits in the Cretaceous and Tertiary rocks of the Western United States. It is used for making refractory linings, water softening, decolorizing oils, thickening drilling muds, and preparing fine grouting fluids. As a mud flush, bentonite is used at a concentration of about 3 lb/ft (super 3) (48.1 kg/m (super 3) ) of water. Syn: Denver mud; volcanic clay. See also: clay.

bentonitic clay
 * Bentonite.

bent sieve
 * A stationary screen constructed in the form of an arc of a circle and arranged as a chute over which the clean coal from a cyclone washer passes to the orthodox rinsing screen. In the United States, the bent screen is used in magnetite recovery from cyclone washers.

benzenol
 * See: phenol.

benzol indicator
 * A portable instrument designed specif. for measuring low concentrations of benzol, which are potentially dangerous to the health of personnel.

beraunite
 * A monoclinic mineral, Fe (super 2+) Fe (super 3+) (sub 5) (PO (sub 4) ) (sub 4) (OH) (sub 5) .4H (sub 2) O ; a secondary mineral in iron deposits; an alteration product of primary phosphates in pegmatites.

berdan
 * A circular, revolving, inclined iron pan in which concentrates are ground with mercury and water by an iron ball.

Berek compensator
 * In polarized-light microscopy, an optical device of variable compensation for analysis of birefringence. CF: accessory plate.

bergalite
 * A pitchy black dike rock containing small phenocrysts of haueyne, apatite, perovskite, melilite, and magnetite in a groundmass of the same minerals with nepheline, biotite, and brown interstitial glass; from Kaiserstuhl, Oberbergen, Baden, Germany. Syn: bergalith.

bergalith
 * See: bergalite.

bergbutter
 * Various salts, commonly halotrichite.

bergenite
 * Occurs naturally at Bergen an der Trieb, Saxony, with other uranium minerals; named from locality, the older name being rejected as implying a barian phosphuranylite rather than the barium analogue. Syn. for barium-phosphuranylite.

Berglof process
 * A method of direct reduction of iron ore. The reduction of the ore was carried out in interchangeable containers. The ore was heated to the reduction temperature in one container, and then this container was moved into the reducing zone.

berkeleyite
 * See: lazulite.

berkelium
 * The element having the atomic number 97, the discovery of which was announced by Thompson, Ghiorso, and Seaborg in 1950. They produced an isotope of 4.5 h half-life, berkelium 243, by helium ion bombardment of americium 241. Symbol, Bk; valences, 3 and 4; and the mass number of the most stable isotope, 249.

Berlin blue
 * In optical mineralogy, an anomalous interference color of the first order; e.g., some epidotes.

Berlin iron
 * A soft iron containing phosphorus, which makes very fine smooth castings and is used for ornaments and jewelry.

berm
 * a. A horizontal shelf or ledge built into the embankment or sloping wall of an open pit or quarry to break the continuity of an otherwise long slope and to strengthen its stability or to catch and arrest slide material. A berm may be used as a haulage road or serve as a bench above which material is excavated from a bank or bench face. CF: bench.

b. The space left between the upper edge of a cut and the toe of an embankment. c. An artificial ridge of earth. d. Terraces that originate from the interruption of an erosion cycle with rejuvenation of a stream in the mature stage of its development and renewed dissection, leaving remnants of the earlier valley floor above flood level. e. A nearly horizontal portion of the beach or backshore formed by the deposit of material by wave action. Some beaches have no berms; others have one or several. See also: bank height.

bermanite
 * A monoclinic mineral, Mn (super 2+) Mn (super 3+) (sub 2) (PO (sub 4) ) (sub 2) (OH) (sub 2) .4H (sub 2) O ; in pegmatites.

berm interval
 * Vertical distance from crest of berm to its underlying toe, as in a bank or bench.

bernardinite
 * Originally described by Stillman as fossil resin, but later shown by Stanley-Brown to be a fungus impregnated by resinous material.

bernstein
 * a. A fossil resin found in and in association with lignite beds of Eocene age. Commonly occurring in many European localities, and is esp. abundant in areas bordering the Baltic coast. See also: amber.

b. German name for amber.

berthierine
 * A monoclinic mineral, (Fe (super 2+) ,Fe (super 3+) ,Mg) (sub 2-2D3) (Si,Al) (sub 2) O (sub 5) (OH) (sub 4) of the kaolinite-serpentine group; (super ) dark steel-gray; in low-temperature vein deposits. Syn: martourite.

berthonite
 * A discredited name for bournonite.

bertrandite
 * An orthorhombic mineral, 4[Be (sub 4) Si (sub 2) O (sub 7) (OH) (sub 2) ]; colorless to clear pale yellow and shows heart-shaped twins; in pegmatites; a source of beryllium. See also: beryllium disilicate.

Bertrand lens
 * A removable lens in the tube of a polarized-light microscope used to converge light to form an interference figure.

Bertrand process
 * A heavy-fluid coal cleaning process that utilizes a calcium chloride solution as separating medium and is applicable only to deslimed feed. It differs from the Lessing process in that the raw coal is introduced into the system countercurrent fashion, from water to separating solution, the purified coal and the waste being withdrawn in a similarly countercurrent fashion. Coal containing less than 1% ash is said to be obtained by this process.

beryl
 * A hexagonal mineral, Be (sub 3) Al (sub 2) Si (sub 6) O (sub 18) ; green, blue-green, and other pale tints; in granite pegmatites, mica schists, and an accessory mineral in felsic igneous rocks; the chief source of beryllium. Transparent and colored gem varieties include emerald, aquamarine, morganite, heliodor, golden beryl, bixbite, and vorobievite.

beryllides
 * A group of intermetallic compounds of potential interest as special ceramics. Cell dimensions and types of structure have been reported for the beryllides of titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, and tantalum.

berylliosis
 * An occupational disease caused by the inhalation of fumes liberated during the reduction of beryllium. Beryllium is thought to play the principal role, aggravated by fluorine, and to affect all organs, particularly the larger protective glands, rather than the respiratory apparatus alone.

beryllite
 * A hydrous silicate of beryllium, Be (sub 3) SiO (sub 4) (OH) (sub 2) .H (sub 2) O, as an alteration product of epididymite.

beryllium
 * An element belonging to the alkaline earth metals. Symbol, Be. Beryl and bertrandite are the most important commercial sources of the element and its compounds. Aquamarine and emerald are the precious forms of beryl. Used in nonsparking tools, high-speed aircraft, missiles, spacecraft, communications satellites, and X-ray lithography for microminiature integrated circuits, as well as in nuclear reactors and computers. Beryllium and its salts are toxic.

beryllium aluminate
 * BeAl (sub 2) O (sub 4) ; mol wt, 126.97; orthorhombic; sp gr, 3.76; source of beryllium. Syn: chrysoberyl.

beryllium carbide
 * Be (sub 2) C ; decomposes above 2,950 degrees C. Used as a moderator in nuclear application. Molecular weight, 30.04; yellow; hexagonal; and sp gr, 1.90 at 15 degrees C.

beryllium disilicate
 * Be (sub 4) Si (sub 2) O (sub 7) (OH) (sub 2) ; mol wt, 238.23; orthorhombic; sp gr, 2.6. Syn: bertrandite.

beryllium nitride
 * Be (sub 3) N (sub 2) ; molecular weight, 55.05; colorless; isometric; and melting point, 2,200 + or - 100 degrees C.

beryllium oxide
 * A white powder; hexagonal; BeO. Used in the preparation of beryllium compounds and in ceramics and refractories. Melting point, 2,570 degrees C; and sp gr, 3.02. Bodies high in BeO have extremely high thermal conductivity (in the range of metals) and also possess high mechanical strength. Used in nuclear reactors because of its refractoriness, high thermal conductivity, and ability to act as a moderator for fast neutrons, reducing them to thermal speeds. Beryllia ceramics are used for electronic components and for crucibles for melting uranium and thorium. Syn: bromellite.

beryllonite
 * A monoclinic mineral, NaBePO (sub 4) ; colorless or yellow; forms transparent, topazlike pseudo-orthorhombic crystals.

beryloid
 * In crystallography, the dihexagonal bipyramid, common in crystals of beryl.

beryloscope
 * See: emerald glass.

beryl preferential stain process
 * A quick, simple method for determining the amount of beryl in a mineral sample. The samples are placed in a hot solution of sodium hydroxide, which etches the beryl grains in the sample; they then are stained an intense blue with another reagent to enable counting under a microscope.

berzelianite
 * An isometric mineral, Cu (sub 2) Se ; silver-white in fresh break; sp gr, 6.7. (super ) ; dimorphous with bellidoite.

berzeliite
 * An isometric mineral, (Ca,Na) (sub 3) (Mg,Mn) (sub 2) (AsO (sub 4) ) (sub 3) ; commonly massive; bright yellow to orange-yellow. Syn: pyrrhoarsenite.

Bessemer
 * Any product of the Bessemer process, such as Bessemer steel, iron, etc.; named from Henry Bessemer, who patented the process in 1855; used also attributively as Bessemer converter, flame, or method.

Bessemer afterblow
 * In the basic Bessemer process of steelmaking, the continuation of the blowing cycle after the oxidation of the silicon, manganese, and carbon content of the charge is complete, and during which the phosphorus and sulfur contents of the charge are reduced.

Bessemer blow
 * In the Bessemer process of steelmaking, the period of the blowing cycle during which the oxidation of the silicon, manganese, and carbon content of the charge takes place.

Bessemer converter
 * A pear-shaped steel shell lined with a refractory material containing a number of holes or ports in the bottom or side through which air is blown through the molten pig iron charge. The converter is mounted on trunnions about which it may be tilted to charge or tap. Molten pig iron is charged into the converter, and air is blown through the molten metal to oxidize the impurities, thus making steel.

Bessemer iron ore
 * See: Bessemer ore.

Bessemer matte
 * In the extraction of copper from sulfide ores, the liquid that remains in the converter at the end of the blow. It is essentially molten nickel sulfide or a solution of copper and nickel sulfides.

Bessemer ore
 * An iron ore containing very little phosphorus (generally less than 0.045%). Named for suitability in the Bessemer process of steelmaking. Syn: Bessemer iron ore.

Bessemer pig iron
 * Pig iron with sufficiently low phosphorus (0.100% maximum) to be suitable for use in the Bessemer process.

Bessemer process
 * A method, historically important but no longer in use, in which molten pig iron is charged in a Bessemer converter and air is blown through the molten metal to oxidize the impurities, thus making steel. This process is no longer in use.

beta
 * In crystallography, the angle between the a and c axes. CF: alpha; gamma.

beta chalcocite
 * See: chalcocite.

betafite
 * An isometric mineral, (Ca,Na,U) (sub 2) (Ti,Nb,Ta) (sub 2) O (sub 6) (OH); pyrochlore group; forms a series with pyrochlore; name assigned to members of the series having uranium greater than 15%; radioactive; in granitic pegmatites. CF: uranpyrochlore.

beta particle
 * An elementary particle emitted from a nucleus during radioactive decay. It has a single electrical charge and a mass equal to 1/1837 that of a proton. A negatively charged beta particle is physically identical to an electron. If the beta particle is positively charged, it is called a positron.

beta quartz
 * Quartz formed at a temperature between 573 degrees C and 870 degrees C. The commonest examples are the bipyramidal quartz crystals found as phenocrysts in quartz porphyries.

beta ray
 * A ray of electrons emitted during the spontaneous disintegration of certain atomic nuclei.

beta tin
 * Metallic tin in its common, massive form.

betatron
 * A doughnut-shaped accelerator in which electrons are accelerated by a changing magnetic field.

beta zinc sulfide
 * Colorless when pure; isometric; ZnS; mol wt, 97.43; sp gr, 4.102 at 25 degrees C, and ranges from 3.90 to 4.11; Mohs hardness, 3.5 to 4.0; luster, resinous to adamantine; transformation temperature to alpha zinc sulfide, 1,020+ or -5 degrees C; sublimes at 1,180 degrees C or 1,185 degrees C; melting point, 1,850 degrees C (at 150 atm or 15.2 MPa); insoluble in water; and very soluble in acids. Occurs as the mineral sphalerite, which is nearly colorless, white, yellow, red, green, brown, and black; has perfect dodecahedral cleavage; and is soluble in hydrochloric acid. Sphalerite is the principal ore of zinc, a source of cadmium, and a source of sulfur for manufacturing sulfur dioxide, sulfuric acid, and other sulfur compounds. Also called sphalerite; zinc blende; zincblende; blende; black jack. See also: sphalerite; zinc sulfide. CF: alpha zinc sulfide.

betechtinit
 * See: betekhtinite.

betekhtinite
 * Orthorhombic needles, Cu (sub 10) (Fe,Pb)S (sub 6), in ores from Mansfeld, Germany. Syn: betechtinit.

Bethell's process
 * A process for creosoting timber (such as track sleepers) to extend its useful life. The timber is first dried, then placed in a cylinder and subjected to partial vacuum, and finally impregnated with creosote under pressure. See also: open-tank method; timber preservation.

between-laboratory tolerance
 * The maximum acceptable difference between the means of two determinations carried out by two different laboratories on representative samples taken from the same bulk sample after the last stage of the reduction process.

beudantite
 * a. A trigonal mineral, PbFe (super 3+) (sub 3) (AsO (sub 4) )(SO (sub 4) )(OH) (sub 6) ; crystallizes in green to black rhombohedra.

b. A mineral group.

bevel cut
 * Any style of cutting with a large table joined to the girdle by one, or possibly two, bevels and a pavilion that may be step cut, brilliant cut, or any style. Used mostly for opaque stones and intaglios. Bevel-cut shapes include round, square, rectangular, oblong, oval, pendeloque, navette, heart, diamond, horseshoe, shield, pentagon, and hexagonal shapes. The style is used predominantly for less valuable gems. Syn: table cut.

bevel gear
 * a. A cone-shaped gear encircling the drive rod in a diamond-drill swivel head, which meshes with a matching gear attached to the drive shaft from the drill motor. By means of these gears, the drill-string equipment can be made to rotate. Syn: miter gear.

b. Any gear, the teeth of which are inclined to the shaft axis of the gear. c. A gearwheel that transmits power between two shafts that meet at an angle. If at a right angle and the wheel is of the same size, it is called a miter gear.

beyerite
 * A tetragonal mineral, (Ca,Pb)Bi (sub 2) (CO (sub 3) ) (sub 2) O (sub 2) ; forms minute tetragonal crystals and earthy masses; a secondary bismuth mineral.

B.H. bit
 * a. A noncoring or blasthole bit.

b. A CDDA standard-size noncoring bit having a set outside diameter of 1 in (2.54 cm). Normally referred to as a 1-in B.H. bit.

B-horizon
 * The layer of a soil profile in which material leached from the overlying A-horizon is accumulated. Syn: zone of accumulation; zone of illuviation. See also: A-horizon.