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

Haanel depth rule
 * A rule of thumb for estimating the depth of a magnetic body, which is valid if the body may be regarded as magnetically equivalent to a single pole. The depth of such a pole is equal to the horizontal distance from the point of maximum vertical magnetic intensity to the points where the intensity is one-third of the maximum value.

Haarmann plow
 * See: scraper box plow.

Haase furnace
 * A muffle furnace of the McDougall type, in which the hearths are separated by suitable flues through which the products of combustion from the fireplace pass.

Haase system
 * A system of shaft sinking through loose ground or quicksand by piles in the form of iron tubes connected together by webs. Their downward movement is facilitated by water under pressure that is forced down the tubes to wash away the loose material from underneath their points.

habit
 * a. A general term for the outward appearance of a mineral or rock.

b. The characteristic or typical crystal form, combination of forms, or other shape of a mineral, including irregularities.

hachure
 * One of a series of short, straight, evenly spaced, parallel lines used on a topographic map for shading and for indicating surfaces in relief (such as steepness of slopes), drawn perpendicular to the contour lines. Hachures are short, broad (heavy), and close together for a steep slope, and long, narrow (light), and widely spaced for a gentle slope, and they enable minor details to be shown but do not indicate elevations above sea level. Etymol: French. Syn: hatching; hatchure. v. To shade with or show by hachures.

hachure map
 * A map that represents the topographic relief by means of hachures.

hack hammer
 * A hammer resembling an adz, used in dressing stone.

hackly
 * The property shown by certain minerals or rocks of fracturing or breaking along jagged surfaces, e.g., broken iron.

hackly fracture
 * A mineral's habit of breaking along jagged, irregular surfaces with sharp edges.

hackmanite
 * A sulfur-rich variety of sodalite.

hacksaw structure
 * Irregular, saw-shaped terminations of crystals (such as of augite) or grains due to intrastratal solution.

hade
 * The complement of the dip; the angle that a structural surface makes with the vertical, measured perpendicular to the strike. It is little used. See also: dip; rise. Syn: underlay.--v. To incline from the vertical.

Hadsel mill
 * Early form of autogenous grinding mill, in which comminution resulted from the fall of ore on ore during the rotation of a large-diameter horizontal cylinder.

Haenisch and Schroeder process
 * A method for the recovery of sulfur as liquid sulfurous anhydride from furnace gases.

hafnium silicate
 * A compound analogous to zircon, therefore, the suggested name hafnon. It can be synthesized from the oxides at 1,550 degrees C. Thermal expansion (150 to 1,300 degrees C), 3.6 X 10 (super -6).

hafnium titanate
 * Special refractory compositions have been made by sintering mixtures of HfO (sub 2) and TiO (sub 2) in various proportions. The melting point of these sintered bodies was approx. 2,200 degrees C; there appeared to be a phase change at about 1,850 degrees C. Some of the compositions had negative thermal expansions.

hag
 * a. To cut as with an ax; to cut down the coal with the pick.

b. Scot. A cut; a notch. c. N. of Eng. A quagmire or pit in mossy ground; any broken ground in a bog.

haeggite
 * A monoclinic mineral, V (sub 2) O (sub 2) (OH) (sub 3) ; forms black crystals in sandstone, Wyoming.

hag principle
 * The system under which a skilled miner employs an unskilled helper.

haiarn
 * In Wales, a term for iron.

hailstone bort
 * Variety of bort built of concentric shells of clouded diamond and cementlike material. See also: bort.

hair copper
 * See: chalcotrichite.

hair pyrite
 * See: millerite.

hair salt
 * Common name for efflorescences of hairlike, acicular, or fibrous crystals of epsomite or other hydrous sulfates in caves and old mine workings. See also: alunogen.

hairstone
 * Quartz thickly penetrated with hairlike crystals of rutile, actinolite, or some other mineral. CF: hedgehog stone.

hair zeolite
 * May be natrolite, scolecite, or mesolite.

half-and-half plane
 * Scot. In a direction midway between plane course and end course. See also: half-course.

half bearings
 * Bearings such as are used on railway cars where the load is constantly in one direction and is sufficiently heavy to hold the journal against the bearing.

half blinded
 * Scot. Two ends driven off a plane, one on each side and not opposite each other by half their width.

half-cell
 * An electrode immersed in a suitable electrolyte designed for measurements of electrode potential.

half-course
 * A drift or opening driven at an angle of about 45 degrees to the strike and in the plane of the seam. See also: half-and-half plane.

half end
 * York. See: horn coal.

half headers
 * Term applied to material that amounts to a large cap piece. They are used by sawing a header in two and placing one or more timbers under the half header on the same side of the track. Two timbers are generally placed under the half header and the end allowed to extend out over the haulage. The term half header should not be applied to regular cap pieces.

half-life
 * a. The time in which one-half of the atoms in a radioactive substance disintegrate.

b. The time in which the quantity of a particular radioactive isotope is reduced to one-half of its initial value. Syn: half-period.

half-marrow
 * Newc. Youngsters, of whom two do the work of one loader.

half-period
 * See: half-life.

half-round nose
 * See: medium-round nose.

half set
 * In mine timbering, one leg piece and a collar.

half-value distance
 * The horizontal distance between the points of maximum and half-maximum values in a symmetrical anomaly, usually either gravity or magnetic. It is useful in estimating the depth of the geologic feature that causes the anomaly.

half-wave rectifier
 * A rectifier that changes single-phase alternating current into pulsating unidirectional current, utilizing only one-half of each cycle.

half width
 * Half the width of a simple anomaly (esp. a gravity or magnetic anomaly) at the point of half its maximum value. For simple models the maximum depth at which the body causing the anomaly can lie can be calculated from the half width.

halide
 * A fluoride, chloride, bromide, or iodide.

Halimond tube
 * Miniature pneumatic flotation cell, operated by hand. Widely used in ore testing, for examination of small samples under closely controllable conditions of flotation.

halite
 * An isometric mineral, 4[NaCl] ; cubic cleavage; soft; salty tasting; forms disseminated grains or crystals in sedimentary rocks, or aggregates of large cubic crystals; granular to massive, the latter as extensive sedimentary beds ranging in thickness from less than 1 mm to more than 50 m, also in convoluted masses called salt domes; a typical constituent of playa lake deposits in arid regions. Syn: rock salt; common salt; salt.

halitic
 * Composed partly or wholly of halite; esp. said of a sedimentary rock containing halite as cementing material, such as halitic sandstone.

haelleflinta
 * Sw. A dense, compact, metamorphic rock consisting of microscopic quartz and feldspar crystals, with occasional phenocrysts and sometimes hornblende, chlorite, magnetite, and hematite. It is associated with gneisses, but is of obscure origin. See also: porcellanite.

Hallett table
 * A table of the Wilfley type, except that the tops of the riffles are in the same plane as the cleaning planes and the riffles are sloped toward the wash-water side.

Hallinger shield
 * A tunneling shield of Hungarian design, successfully employed for tunneling at Dortmund and under the Danube. It is valuable for working in very soft ground. It incorporates a mechanical excavator and does not entail the use of timbering to protect the miners.

halloysite
 * a. A monoclinic mineral, 2[Al (sub 4) Si (sub 4) (OH) (sub 8) O (sub 10) ]; kaolinite-serpentine group; made up of slender tubes as shown by electron microscopy; a gangue mineral in veins. Syn: metahalloysite.

b. Used as a group name to include natural "halloysite minerals" with different levels of hydration, as well as those formed artificially. See also: alum salt.

Hall process
 * The first commercially successful method for manufacturing aluminum; the purified oxide is dissolved in fused cryolite and then electrolyzed. Syn: Heroult process.

Hall-Rowe wedge
 * A tapered concave metal plug or wedge that can be set in a drill hole at a predetermined depth and bearing to deflect or straighten an off-course borehole. See also: wedge.

halo
 * a. A circular or crescentic distribution pattern about the source or origin of a mineral, ore, mineral association, or petrographic feature. It is encountered principally in magnetic and geochemical surveys. Some halos are primary, formed either at the same time as the host rock or at the same time as associated mineral deposits, and some are secondary, formed by surficial alteration of the associated mineral deposit. Syn: aureole. CF: dispersion pattern. See: wall-rock halo.

b. Discoloration of a mineral, viewed in thin section, in the form of a ring. Most halos of this sort are caused by radiation damage by alpha particles emitted from uranium- and thorium-bearing mineral inclusions.

halocline
 * A steep ascendent of salinity. This has an effect on refraction of sound waves, since sound velocity increases with increasing salinity.

halokinesis
 * See: salt tectonics.

halotrichite
 * a. A monoclinic mineral, 4[Fe (super 2+) Al (sub 2) (SO (sub 4) ) (sub 4) .22H (sub 2) O] ; forms a series with pickeringite in which magnesium replaces ferrous iron; soft; a weathering product of pyritic rocks in mines; also in arid regions and around fumaroles.

b. The mineral group apjohnite, bilinite, dietrichite, halotrichite, pickeringite, and redingtonite. Syn: feather alum; iron alum.

haloxylin
 * A mixture of yellow prussiate of potash, niter, and charcoal used as an explosive.

hamburgite
 * An orthorhombic mineral, 8[Be (sub 2) (BO (sub 3) )(OH)] ; in alkali pegmatites and in placers.

hammada
 * An extensive, nearly level, upland desert surface that is either bare bedrock or bedrock thinly veneered by pebbles, smoothly scoured and polished and generally swept clear of sand and dust by wind action; a rock desert of the plateaus, esp. in the Sahara. The term is also used in other regions, as in Western Australia and the Gobi Desert. Etymol: Arabic, hammadah.

hammer
 * a. Term for drive hammer, a heavy sleeve-shaped weight used for driving drill pipe or casing into overburden or soft rock.

b. To pound or drive with pilehammerlike blows delivered by a drive hammer.

hammer breaker
 * An impact type of breaker consisting of a number of swinging bars or steel hammers hinged to a horizontal shaft that rotates at high speed.

hammer drill
 * a. A light, mobile, and fast-cutting drill in which the bit does not reciprocate but remains against the rock in the bottom of the hole, rebounding slightly at each blow. There are three types of hammer drills; drifter, sinker, and stoper.

b. A development of the piston drill in which the drill steel is not attached to the piston but remains in the hole, the piston delivering a rapid succession of light hammer blows. The drill steel is frequently hollow so that air or water may be driven through to cool the bit and clean the hole. Rotation of the bit is automatic. Also known as jackhammer. c. A percussive drill. d. A rock drill powered by compressed air that reciprocates a free piston, causing it to strike the shank of the drill steel. When of light construction, a hand hammer drill, otherwise supported on a tripod or bar.

hammermill
 * a. A pulverizing unit consisting of a rotor, fitted with movable hammers, that is revolved rapidly in a vertical plane within a closely fitting steel casing. The hammers hit falling rock, which is fractured on impact, or by collision with other rocks or with the casing. When sufficiently reduced in size, the pulverized rock escapes through grids in the casing. Syn: beater mill. CF: disintegrator; impact crusher; impact mill.

b. Coal crusher in which the blow is induced with the aid of centrifugal force. The coal is broken with the impact and usually dragged across grate bars in the bottom of the unit. See also: ring crusher.

hammerpick
 * A compressed-air-operated hand machine used by miners to break up the harder rocks in a mine. It consists mainly of a pick and a hammer operated by compressed air. The hammer driving the pick is set in a cylinder, where the compressed air enters and presses the hammer, which in turn drives the wedge-shaped edge of the pick into the rock in short sufficient shocks of from 1,500 to 2,000 blows per minute. See also: poll pick.

hammochrysos
 * A stone, the appearance of which suggested sand veined with gold, perhaps mottled jasper.

hammock structure
 * The intersection of two vein or fracture systems at an acute angle.

hand
 * Measurement of height of mine haulage animals equivalent to 4 in (10.2 cm).

hand auger
 * A screwlike tool much like a large carpenters' bit or a short cylindrical container with cutting lips attached to a rod and operated by hand and used to bore shallow holes and obtain samples of soil and other relatively unconsolidated near-surface materials. CF: auger.

hand boring
 * The drilling of holes by hand for site investigations or for the exploration of shallow mineral deposits. The hand drill is used for depths of about 15 m and where the ground is loose or not too hard. CF: auger.

hand cable
 * A flexible cable used principally in making electrical connections between a mining machine and a truck carrying a reel of portable cable. Also called head cable; butt cable.

hand cleaning
 * The removal by hand of impurities from coal, or vice versa.

hand cobbing
 * See: cobbing.

hand drilling
 * A historical method of drilling blastholes in rock by hammer and a hand-held steel or bit. Single-jack drilling was done by one miner. In double-jack drilling, one miner held the steel for one or two strikers with hammers.

hand electric lamp
 * A hand lamp, with battery and fitments similar to a cap lamp except that it forms a self-contained unit.

hand filling
 * a. Scot. Loading coal from face by hand.

b. Eng. Loading coal from face by hand, but small coals are loaded separately from large lumps. c. See: sublevel stoping.

hand frame
 * An iron barrow used in a foundry.

hand gear
 * starting.

hand hammer
 * Any hammer wielded by hand. A blacksmith's (or miner's) hammer used with one hand as distinguished from a heavier hammer or sledge.

hand hammer drill
 * An ordinary rock drill held in the hand and not mounted on a bar or column. The air leg support is now widely used in tunnels and rock drilling generally.

hand jig
 * Manually operated moving-screen jig used to treat small batches of ore. The jig box is fixed to a rocking beam and moved up and down in a tank of water.

hand lamp
 * A portable battery-operated lamp incorporating a tungsten filament light source within a glass of the dome or well-glass type and providing maximum illumination in the horizontal plane.

hand lead
 * A lead weight attached to a lead line of up to 100 fathoms (183 m), used in hydrographic surveying.

handling plant
 * Equipment for the mechanical movement of dirt, ore, coal, or other material either horizontally or up an incline, by some form of conveyor, bucket, chain, or rope.

hand loader
 * A miner who loads coal by shovel rather than by machine. See also: loader.

hand mining
 * The working and winning of coal or mineral by hand and not by machines. Broadly, hand coal mining would imply hand holing, shot firing, and hand filling.

handpicked coal
 * Coal from which all stones and inferior coal have been picked out by hand; large lumps.

handpicking
 * Manual removal of selected fraction of coarse run-of-mine ore, usually performed on picking belts (belt conveyors) after screening away small material, perhaps washing off obscure dirt, and crushing pieces too large for the worker to handle. Hard sorting (Rand) describes picking of banket when up to 30% of waste rock is removed. See also: sorting.

hand sampling
 * a. In prospecting, valuation, and control, use of manual methods for detaching and reducing to an appropriate size representative samples of ore.

b. One of the major breakdowns in ore sampling that includes grab sampling, trench or channel sampling, fractional selection, coning and quartering, and pipe sampling. These methods are used in sampling small batches of ore, etc. CF: mechanical sampling.

hand scraper
 * See: stope scraper.

hand selection
 * The selection by hand of pieces of coal with certain specific qualities according to surface appearance.

handset
 * A drilling bit in which the diamonds are set into holes drilled into a malleable-steel bit blank and shaped to fit the diamonds. The hand method has been almost completely superseded by mechanical setting methods. CF: mechanical set.

hand specimen
 * A piece of rock of a size that is convenient for megascopic study and for preserving in a study collection.

hand spraying
 * A method of dust prevention used in hand-won faces, or in conjunction with wet cutting in thick seams. The sprays are controlled by the colliers who wet the face and the broken coal before loading. Sprays must be connected with the pipeline through the face by means of flexible hoses; one spray for every 20 yd (18.3 m) of face is usually sufficient.

hand tramming
 * Pushing of cars by manpower. It is limited to mines of small output, to prospects, and to work where mechanical haulage would not be justified. See also: manual haulage.

hand whip
 * A counterpoised sweep for raising water from shallow pits.

handyman
 * A person employed to do various kinds of work.

hang
 * a. To suspend casing or pipe in a borehole in a clamp resting on blocks at the collar of the hole.

b. To suspend drill string or other downhole equipment in the drill derrick or tripod either on the hoisting line or on hooks provided in the crown block for that purpose.

hanger
 * a. See: hanging wall; hanging bolts.

b. Scot. The hook of a miner's lamp. c. Something that hangs, overhangs, or is suspended. d. A frame containing a bearing for a shafting.

hangfire
 * An explosive charge that is not properly detonated and burns and may eventually result in a detonation at some nondetermined time. See also: hung shot.

hanging bolts
 * Rods of round iron, used in shaft construction to suspend wallplates. In concrete-lined shafts hanging rods give reinforcement, the top set being concreted into the shaft collar and others hooked on below, with periodic consolidation in strong rock strata as the shaft is deepened. Sometimes called hangers.

hanging coal
 * A portion of the coal seam which, by undercutting, has had its natural support removed.

hanging deal
 * Aust. Planks used to suspend a lower curb from the one above it, in cases where backing deals are necessary.

hanging its water
 * Scot. The bucket is said to hang its water when it fails to pump on account of a faulty valve, or air between the bucket and the valve, the column of water above the bucket being sufficient to prevent the opening of the bucket lids.

hanging-on
 * Eng. The pit bottom, level, or inset at which the cages are loaded.

hanging pulley
 * A small fenced pulley hung from the roof or side of a haulage road in which the tail rope of a main-and-tail haulage is suspended. It keeps the rope (which is not used for direct haulage of cars) clear of the roadway and minimizes friction while in motion. The swinging of hanging pulleys and ropes is a hazard to people traveling on the roadway.

hanging scaffold
 * Scot. A movable platform in a shaft attached to a winding rope.

hanging sets
 * Scot. Timbers from which cribs are suspended in working through soft strata.

hanging wall
 * a. The overlying side of an orebody, fault, or mine working, esp. the wall rock above an inclined vein or fault. See also: wall; walls; top wall. Syn: hanger. CF: footwall.

b. Sticking or wedging of part of the charge in a blast furnace.

hanging wall drift
 * In the United States, a horizontal gallery driven in the hanging wall of a vein.

hanging wall of a fault
 * The upper wall of an inclined fault plane.

hang-up
 * Underground, blockage of ore pass or chute by rock.

haplite
 * See: aplite.

hard
 * a. Containing certain mineral salts in solution, esp. calcium carbonate; said of water having more than 8 to 10 grains/gal (137 to 171 mg/L) of such matter to the gallon.

b. Solid; compact; difficult to break or scratch. See also: hardness scale.

hard bottom
 * A condition encountered in some open-cut mines wherein the rock occasionally will not be broken down to grade because of an extra-hard streak of ground or because not enough explosive is used. This is called a "hard bottom"; it interferes with work and puts undue strain on a shovel. Such unbroken ores usually are drilled with a jackhammer and blasted.

hard coal
 * a. All coal of higher rank than lignite.

b. In the United States, the term is restricted to anthracite. See also: anthracite.

hard-coal plow
 * A plow type of cutter loader for cutting the harder coal seams. It consists of stepped kerving bits that precut the coal, leaving the unstressed coal to be cut by the following bits. The kerving bits may be either rigid or swiveling. See also: rapid plow. Syn: Westfalia plow.

hardebank
 * Unaltered kimberlite below the zone of blue ground. CF: blue ground.

hardened steel
 * Steel that has been hardened by quenching from or above the hardening temperature.

hardener
 * An alloy, rich in one or more alloying elements, added to a melt either to permit closer composition control than is possible by addition of pure metals or to introduce refractory elements not readily alloyed with the base metal.

hardening
 * Metallurgical process in which iron or suitable alloy is quenched by abrupt cooling from or through a critical temperature range. See also: precipitation hardening.

hardening media
 * Liquids into which steel is plunged in hardening. They include cold water, various oils, and water containing sodium chloride or hydroxide to increase the cooling power.

hard ground
 * Rock that is difficult to work.

Hardgrove number
 * Empirical index of grindability of ores or minerals, reached as result of comminution of a test sample under stated conditions of control.

Hardgrove test
 * This test utilizes a special grindability mill of the ring-and-ball type, in which a 50-gm portion of closely sized coal is ground for 60 revolutions. This method is of the constant-work type; i.e., a fixed amount of work is expended on each coal, and a grindability value is determined from the size composition of the ground material.

hardhat
 * Slang term for a safety hat.

hardhead
 * a. A hard knob or knot formed by extreme cementation of sandstone.

b. A large, smooth rounded stone found esp. in coarse gravel. c. A tunnel in a coal mine driven through rock. Syn: hard heading. d. A hard, brittle, white residue obtained in refining tin by liquation, containing, among other things, tin, iron, arsenic, and copper. Also, a refractory lump or ore only partly smelted.

hard heading
 * A heading driven in rock. In S. Wales and elsewhere, men employed in hard headings have suffered greatly from silicosis. Syn: hardhead. See also: stone drift.

Hardinge mill
 * Cylindroconical ball mill, made in three sections--a flattish cone at feed end followed by a cylindrical drum, and finishing with a steep cone leading to the discharge trunnion. The tricone mill has wedge-shaped liners in the drum section that turn this into a gentle conic frustrum widest at the feed end.

Hardinge thickener
 * A machine for removing the maximum amount of liquid from a mixture of liquid and finally divided solids. The solids settle out on the bottom of the thickener tank as a sludge, and the clear liquid overflows at the top of the tank. It is used for processing chemical, metallurgical, and coal-washing slurries.

hard kiln
 * A muffle kiln fired at a temperature between that of enamel and gloss kilns.

hard mica
 * Mica that, when slightly flexed or distorted with thumb pressure, generally does not show any tendency to delaminate. Such mica, in thick pieces, will give an almost metallic sound when tapped or dropped on a hard surface.

hard needles (or inclusions)
 * A term applied in the grading of quartz crystals to fairly large needlelike inclusions or imperfections that appear to be hard.

hardness
 * a. Quality of water based on the presence of dissolved calcium or magnesium. See also: hard water. Syn: total hardness.

b. As used by individuals associated with the drilling and bit-setting industry, the relative ability of a mineral to scratch another mineral or to be penetrated by a Knoop indenter. See also: hardness test. c. Of a brittle mineral, the resistance to scratching or abrasion by another mineral, e.g., the Mohs scale of relative hardness, which ranges from 1 (talc) to 10 (diamond), or the Povarennykh scale from 1 (talc [001]) to 15 (bort diamond [111]). See also: hardness scale. d. Resistance of a metal to plastic deformation by indentors of various shapes as defined by the Brinell, Knoop, Rockwell, and Vickers scales.

hardness gage
 * See: hardness points.

hardness pencils
 * See: hardness points.

hardness plates
 * A series of small pieces of minerals of differing hardness, polished flat, and set side by side in cement, for testing hardness of another mineral, which is drawn across one piece after another, beginning with the hardest, until it scratches one.

hardness points
 * Small pieces of minerals of differing hardness, with one end pointed and affixed to small handles of wood, metal, or plastic, to be held in hand and used for testing hardness of another mineral, by ascertaining which points will scratch it. Minerals of hardness 6 to 10 are usually used as points for testing gem stones. Syn: hardness gage; hardness pencils.

hardness scale
 * a. The scale by which the hardness of a mineral is determined as compared with a standard. The Mohs scale is as follows: talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond. Also called Mohs scale. See also: hard; hardness; hardness test.

b. Quantitative units by means of which the relative hardness of minerals and metals can be determined, which for convenience is expressed in Mohs, Knoop, or scleroscope units for minerals and Vickers, Brinell, or Rockwell units for metals.

hardness table
 * Any listing of substances as to their comparative hardness.

hardness test
 * A determination of the relative hardness of a mineral, such as scratch hardness, as made on a specimen, using appropriate hardness-testing apparatus and techniques. See also: hardness; hardness scale.

hardness wheel
 * A hand instrument in which hardness points are set as equidistant spokes of a rimless wheel, permitting a more rapid selection of points in testing hardness.

hardpan
 * a. A layer of gravel encountered in the digging of a gold placer, occurring 1 to 2 m below the ground surface and partly cemented with limonite.

b. A popular term used loosely to designate any relatively hard layer that is difficult to excavate or drill; e.g., a thin resistant layer of limestone interbedded with easily drilled soft shales. c. See: caliche.

hard radiation
 * Ionizing radiation of short wavelength and high penetration.

hard rock
 * a. A term used loosely for igneous or metamorphic rock, as distinguished from sedimentary rock.

b. A rock that is relatively resistant to erosion. c. Rock that requires drilling and blasting for its economical removal. CF: soft rock.

hard-rock drilling
 * Drilling done in dense and solid igneous or highly silicified rocks, which can be penetrated economically only by diamond bits, as opposed to that done in softer rocks easily cut by roller or wing-type rotary bits.

hard-rock geology
 * A colloquial term for geology of igneous and metamorphic rocks, as opposed to soft-rock geology.

hard-rock mine
 * A mine in hard rock; esp. one difficult to drill, blast, and square up.

hard-rock miner
 * A worker competent to mine in hard rock. Usually used to indicate an expert miner as compared with one fit only to mine in soft rocks.

hard rock minerals
 * Solid minerals, as distinguished from oil and gas, esp. those solid minerals found in hard rocks.

hard-rock mining
 * Mining that takes place in igneous and metamorphic rock by means of drilling and blasting to extract the ore.

hard-rock phosphate
 * A term used in Florida for pebbles and boulders of a hard massive homogeneous light-gray phosphorite, showing irregular cavities that are usually lined with secondary mammillary incrustations of calcium phosphate. It is essentially equivalent to the term "white-bedded phosphate" that is used in Tennessee.

hard-rock tunnel boring
 * A technique utilizing a machine called a boring machine to bore large horizontal openings in rock or coal.

hards
 * a. A commercial term for the larger sizes of dull, hard coal, in contrast to brights.

b. See: durain. c. In the United States, this term is used for anthracite.

hard seat
 * See: seat earth.

hard solder
 * Any solder that melts only at a red heat; used in soldering silver, etc.

hard sorting
 * See: handpicking.

hard spar
 * A name applied to both corundum and andalusite.

hard vector
 * Due to the arrangement of the molecules within some mineral crystals, such as diamond, the substance is found to be harder in certain planes or directions in relation to the axes of the mineral crystals. These hard planes are referred to as hard vectors. CF: soft vector. See: vector.

hard water
 * Water that does not lather readily when used with soap, and that forms a scale in containers in which it has been allowed to evaporate; water with more than 60 mg/L of hardness-forming constituents, expressed as CaCO (sub 3) equivalent. See also: hardness; total hardness of water; temporary hardness of water. CF: soft water.

hard way
 * a. A term used in slate quarrying to describe the third direction at right angles to both slaty cleavage and rift, in which there is no tendency to split. It is known as the hard way and designated locally as the sculp.

b. In granite quarrying, the direction at right angles to both rift and run is called the hard way or head grain. See also: cutoff; tough way. Sometimes spelled hardway.

hard white ore
 * Georgia bauxite containing less than 1% ferric oxide.

Hardwick conveyor loader head
 * A dust collector for belt conveyors used at the loading station. The delivery pulley of the main gate conveyor is used to drive a scraper chain. The latter is arranged to run at half the belt speed by means of chains and sprockets, and the scraper chain runs at the bottom of a long hopper to the point where the coal is delivered into the trams. The underbelt fines are collected on the scraper chain after having been released from the belt by means of a snub pulley. The whole arrangement is housed in a sheet-steel cover to which rubber flaps are attached. Side spillage and the escape of dust over the side of the trams is prevented by means of rubber flaps.

hardypick drifting machine
 * A heavy electric rotary drilling machine for blasting work in mine tunneling. It consists of a chassis mounted on continuous tracks, turntable, boom, drilling machines, and various controls, and can be operated by two people.

Harman process
 * A method for producing direct from ore an iron in the form of either sinter or pig that is suitable for charging in steel furnaces. Ore, limestone, and carbon in the form of coal, coke, or oil coke in the proportions of 40:8:5 are dried, crushed to about 1/16 in (1.6 mm), intimately mixed, and fed into the upper end of a sloping rotary kiln.

harmful dust
 * Generally, any airborne particulate matter that is fibrogenic (harmful to the respiratory system), carcinogenic (capable of causing cancer), radioactive, or toxic.

harmless depth theory
 * A hypothesis based largely on the dome theory, which states that there is a certain harmless depth below which mining could be carried on without risk of damage to the surface. Subsidence observations at present working depths do not support this theory.

harmonic
 * A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related.

harmonic crystal
 * A crystal designed to oscillate at an integral multiple of its fundamental frequency.

harmonic folding
 * Folding in which the strata remain parallel or concentric, without structural discordances between them, and in which there are no sudden changes in the form of the folds at depth. Ant: disharmonic folding.

harmotome
 * A monoclinic mineral, (Ba,K) (sub 1-2) (Si,Al) (sub 8) O (sub 16) .6H (sub 2) O ; zeolite group; in hydrothermal veins, vugs in igneous rocks, manganese ores, saline lakes. Syn: cross-stone.

harpolith
 * a. A large, sickle-shaped igneous intrusion that was injected into previously deformed strata and was subsequently deformed with the host rock by horizontal stretching or orogenic forces.

b. Essentially a phacolith with a vertical axis.

harrie
 * Scot. To rob; to take all the coal that can conveniently be mined without attempting to systematically remove the whole. A variation of harry; to strip; despoil; to rob.

harriers
 * Trammers, putters, or drawers employed to convey trucks or tubs from the working face. They may help load the trucks.

harrisite
 * a. Chalcocite pseudomorphous after galena.

b. A phanerocrystalline rock composed essentially of black, lustrous, cleavable olivine with anorthite and a little augite.

Harris process
 * Process for removing arsenic, antimony, tin, and zinc from virgin or secondary lead by agitating the molten metal with molten caustic soda and salt. All undesirable metals are oxidized, and the oxides are dissolved in the caustic, with the exception of silver, which is removed in a subsequent desilvering operation.

harrock
 * Hard chalk.

harrow
 * A pole with teeth in it, which revolves in a puddling trough to puddle auriferous clay.

hartine
 * See: hartite.

hartite
 * Hydrocarbon occurring in brown coal as transparent masses or small, waxy triclinic crystals. Syn: hartine; josen.

Hartley gravimeter
 * An early form (1932) of stable gravimeter consisting of a weight suspended from a spiral spring, a hinged lever, and a compensating spring for restoring the system to a null position.

hartleyite
 * A variety of oil shale from Hartley, New South Wales.

hartsalz
 * Hard salt, a mixture of sylvinite and kieserite, with some anhydrite, found in the Stassfuert salt deposits

hartschiefer
 * A strongly banded and partly schistose rock; associated with other rocks of mylonitic habit, in which the alternating bands have been produced from ultramylonite by recrystallization and metamorphic differentiation.

Harvey process
 * Method of carburizing the surface layers of low-carbon steel, followed by rapid chilling.

harzburgite
 * A variety of peridotite that consists essentially of olivine and enstatite or bronzite.

Harz jig
 * A jig in which pulsion is given intermittently with suction; the periods devoted to them are about equal. See also: hodge jig; jig.

Hasenclever turntable
 * This type of turntable is used as an alternative to the shunt-back or the traverser for changing the direction of mine cars or tubs, either on the surface or underground. A pulley driven by a creeper chain bringing along the cars is on the same vertical axis as the turntable and is so disposed that when a car is on the table two of its wheels rest on its central pulley while the other two rest on the outer edge of the turntable.

hassing
 * See: hasson.

hasson
 * Scot. A vertical gutter between water rings in a shaft. Syn: hassing. See also: gauton.

Hastings beds
 * A series of clay and sand deposits in the Lower Cretaceous of southeast England; the Fairlight Clays at the base of these deposits have been used for brickmaking near Hastings and Bexhill.

hatch conveyor
 * Any of several types of conveyors adapted to loading or unloading bulk materials, packages, or objects to or from ships or barges. See also: belt conveyor CF: portable conveyor.

hatchet stake
 * A small anvil on which to bend sheet metal.

hatchettine
 * A yellowish-white, wax-yellow, or greenish-yellow paraffin wax usually found inside ironstone nodules and geodes in coalbeds or limestone. It melts at 55 to 65 degrees C, is sparingly soluble in boiling alcohol and cold ether, and is decomposed by concentrated sulfuric acid. Syn: mineral tallow. CF: ozocerite.

hatchettite
 * A naturally occurring soft paraffin wax; forms veinlike masses in ironstone nodules associated with coal-bearing strata, South Wales; in limestone cavities, France. Syn: adipocerite; adipocire; mineral adipocire; mineral tallow. See also: grave wax. CF: ozocerite.

hatchettolite
 * A former name for uran-pyrochlore.

hatching
 * a. Brist. An underground way or self-acting inclined plane, in a thin seam of coal, extending from 60 to 80 yd (55 to 73 m) to the rise.

b. See: hachure.

hatchure
 * See: hachure.

Hatfield process
 * Dielectric separation process.

hat rollers
 * Hat-shaped metal guides for ropeways around bends.

hauchecornite
 * The mineral group arsenohauchecornite, bismutohauchecornite, hauchecornite, tellurohauchecornite, and tucekite.

haul
 * a. The distance from the coal face to pit bottom or surface; the distance quarry or opencast products must be moved to the treatment plant or construction site; the distance from the shaft or opencast pit to spoil dump.

b. Average haul; the average distance a grading material is moved from cut to fill. c. In the construction of an embankment by depositing material from a cutting, the haul is the sum of the products of each load by its haul distance.

haulabout
 * A steel barge with large hatchways and coal transporters used for coaling ships.

haulage
 * a. The drawing or conveying, in cars or otherwise, or movement of workers, supplies, ore, and waste both underground and on the surface.

b. In dividing the transportation system according to the area served there is (1) primary or face haulage, (2) secondary haulage, and (3) main-line haulage. See also: transport; intermediate haulage; relay haulage; locomotive haulage; underground haulage. c. Applied generally to track mining as opposed to conveyor mining, although belt conveyor systems are sometimes referred to as belt haulage. d. The system of hauling coal out of a mine. e. S. Afr. A drive used for mechanical transport.

haulage boss
 * In bituminous coal mining, a foreperson who supervises mine haulage operations underground or at the surface.

haulage brake
 * See: brake.

haulage cars
 * Rail haulage cars for surface or mine shaft operations that are used to carry ore and equipment to and from the digging site.

haulage chain
 * In the early days chains were used in haulage in and around mines. Wire rope has displaced them.

haulage clip
 * A device to effect a secure attachment of tub to the haulage top, chiefly with endless rope haulage. The usual type attains the grip on the rope by two jaws that may be tightened by either a screw or a lever movement. The connection of the clip to the tub is usually made to the drawbar by a hook or link. The clip must maintain a sure grip on the rope and be capable of easy and quick manipulation. See also: automatic clip; clip.

haulage conveyor
 * Generally 500 to 3,000 ft (152 to 915 m) in length. It is used to transport material between the gathering conveyor and the outside. Haulage conveyors are commonly classified as either intermediate or main haulage conveyors. See also: underground mine conveyor.

haulage curve
 * A bend in a haulage road, which may be horizontal, vertical, or both. On main haulage roads, curves may be 100 ft (30.5 m) in radius or more. With a good rail track and smooth curves, haulage speeds up to 20 mph (32.2 km/h) can be maintained. A useful rule for determining the minimum radius of curvature for tramming is R = 12 to 15 x W; for locomotive haulage R = 20 to 25 x W, where W is the maximum wheel base of the rolling stock or locomotive.

haulage drum
 * A large cylinder on to which the steel haulage rope is coiled. The rope is attached to the drum by passing it inside and looping it about the drum shaft, and securing the loose end to the rope by rope clamps. The excess length of rope is coiled around the drum to provide for recapping during its useful life.

haulage hand
 * A worker fully employed on the haulage system in a mine.

haulage mine locomotive
 * See: electric haulage mine locomotive.

haulage plant
 * A mechanical installation for the tramming of rock, ore, or coal; operated by ropes, compressed air, or electricity.

haulage rope
 * a. A rope used for haulage purposes.

b. A wire rope composed of six strands of seven wires each.

haulage stage
 * A mine roadway along which a load is moved by a single form of haulage without coupling or uncoupling of cars and without transfer from one form of haulage to another.

haulageway
 * The gangway, entry, or tunnel through which loaded or empty mine cars are hauled by animal or mechanical power.

haulaway
 * An excavation method that involves hauling the spoil away from the hole.

haulback mining
 * Method of surface mining in which the overburden is hauled from over the ore or coal in trucks to a holding area and hauled back after the ore or coal has been removed.

haul-cycle time
 * The time it takes the scraper or truck to haul a load to the dumping area and return to position in the loading area.

haul distance
 * The distance measured along the center line or most direct practical route between the center of the mass of excavation and the center of mass of the fill as finally placed. It is the distance material is moved.

hauling
 * The drawing or conveying of the product of the mine from the working places to the bottom of the hoisting shaft, or slope.

hauling engine
 * An engine employed to move tubs on an underground engine plane.

haul road
 * A road built to carry heavily loaded trucks at a good speed. The grade is limited on this type of road and usually kept to less than 17% of climb in direction of load movement.

haunt
 * Coal sold at the pithead.

hausmannite
 * a. A mineral, Mn (super 2+) Mn (sub 2) (super 3+) O (sub 4) . In tetragonal octahedrons and twins; also granular massive, particles strongly coherent. Luster submetallic. Color, brownish-black. Syn: black manganese.

b. A tetragonal mineral, Mn (super 2+) Mn (super 3+) (sub 2) O (sub 4) ; pseudocubic; in submetallic, commonly twinned crystals in high-temperature hydrothermal veins, contact metamorphic deposits associated with felsic igneous rocks; also an alteration product of manganese ores by meteoric waters; associated with psilomelane in the Batesville district, Arkansas.

hauyne
 * An isometric mineral, [(Na,Ca) (sub 4-8) Al (sub 6) Si (sub 6) (O,S) (sub 24) (SO (sub 4) ,Cl) (sub 1-2D2) ] ; sodalite group; crystallizes in dodecahedra and octahedra with dodecahedral cleavage; an accessory mineral in alkaline igneous rocks, esp. extrusives, commonly associated with nepheline or leucite. Also spelled haueyne, hauynite.

hauynite
 * A blue feldspathoid, crystallizing in the cubic system, consisting essentially of silicate of aluminum and sodium with sodium sulfate, (Na,Ca) (sub 4-8) Al (sub 6) Si (sub 6) (O,S) (sub 24) (SO (sub 4) ,Cl) (sub 1-2) . Also spelled haueynite. Also called hauyne. Syn: sapphirine.

haueynitite
 * A plutonic or hypabyssal rock composed chiefly of hauyne and pyroxene, usually titanaugite. Small amounts of feldspathoids and sometimes plagioclase and/or olivine are present. Apatite, sphene, and opaque oxides occur as accessories. See also: haueynophyre.

haueynophyre
 * An extrusive rock similar in composition to a leucitophyre but containing haueyne in place of some of the leucite. Other possible phases include nepheline, augite, magnetite, apatite, melilite, and mica. A partial syn. of haueynitite; some rocks are called haueynophyre when haueyne is a conspicuous mineral but not necessarily a major constituent. See also: haueynitite.

Hauy's law
 * Every crystal of precise chemical structure and purity has a specific and characteristic shape.

Hauzeur furnace
 * A double furnace for the distillation of zinc wherein waste heat from one set of retorts is utilized for heating the second set.

Hawaiian peridot
 * A gem-quality variety of olivine (forsterite) in Hawaii; forms phenocrysts in basalt; also in derived sands.

hawaiite
 * a. A gem variety of olivine from the lavas of the Hawaiian Islands. It contains little iron and is pale green.

b. As defined by Iddings in 1913, an olivine basalt with andesine as the normative plagioclase (thus differing from true basalt, in which the normative plagioclase is more calcic). It generally, but not always, lacks normative quartz, and commonly contains normative and modal olivine. Hawaiite is intermediate in composition between alkali olivine basalt and mugearite, and grades into both. See also: mugearite; trachybasalt.

hawk's-eye
 * A transparent colorless quartz containing closely packed, parallel fibers of crocidolite that impart to it a blue color. In form and sheen, it resembles tigereye to which it alters geologically. Differs from sapphire quartz, in which fibers are not parallel. Also spelled hawkeye. CF: tiger's-eye.

hawleyite
 * An isometric mineral, CdS ; sphalerite group; dimorphous with greenockite; occurs as yellow powder on sphalerite.

hawser
 * A large rope, varying from 5 to 24 in (12.7 to 61.0 cm) in circumference, of 6 to 9 strands and left-handed twist.

hawser laid
 * a. Of fiber rope, one with three strands of yarn twisted left-handed, these strands being laid up right-handed.

b. If wire rope, it is called cable laid.

Hayden process
 * A series method of electrolytic refining. Unrefined copper anodes are suspended in an acid electrolyte; one side of each then acts as an anode and the other as a cathode.

Hay mist projector
 * This projector can be made at any colliery workshop from a few short pieces of piping and an old oil drum. It may be fixed in the drum or in an open tank of larger capacity placed 12 to 15 yd (11.0 to 13.7 m) back from the face of the hard heading. To the water in the drum, powdered washing soda is added at the ratio of 4 oz (113.4 g) to 5 gal (18.9 L) of water. About 2 min before firing, compressed air is turned on and ejections of water in the form of a coarse mist fill the heading. This continues for a period of 6 min after the firing. In this manner, the heading is filled with a mist of droplets that outnumber the dust particles; the latter are effectively wetted or become attached to the droplets, with the result that the dust rapidly settles out of the air. This mist projector has a high efficiency, particularly where the ventilation current is low.

hazel
 * N. of Eng. In coal mining, a tough mixture of sandstone and shale; also, freestone, flagstone, or chert.

Hazelett process
 * A method for casting liquid metal or steel continuously into rolls for sheet or plate. The steel is poured on to the outer surface of a broad steel cylinder of very large diameter (up to 6 m) that is supported and revolved by a roller turning inside it. The molten steel is carried a short distance to a roller revolving above the ring, which rolls the almost solidified steel into a thin plate or strip.