FALSE BEDROCK A hard or relatively tight formation within a placer deposit, at some distance above true bedrock, upon which gold concentrations are found. Clay, volcanic ash, caliche or "tight" gravel formations can serve as false bedrocks. A deposit may have gold concentrations on one or more false bedrocks, with or without a concentration on true bedrock.
FANNING CONCENTRATOR See - pinched sluice.
FINE GOLD 1. Pure gold, i.e., gold of 1000-fineness. 2. Gold occurrmg in small particles such as those which would pass a 20-mesh screen but remain on 40-mesh.
FINENESS The proportion of pure gold in bullion or in a natural alloy, expressed in parts per thousand. Natural gold is not found in pure form; it contains varying proportions of silver, copper and other substances. For example, a piece of natural gold containing 150 parts of silver and 50 parts of copper per thousand, and the remainder pure gold, would be 800·fine. The average fineness of placer gold obtained in California is 885.
FINES 1. The sand or other small-size components of a placer deposit. 2. The material passing through a screen during washing or other processing steps of a placer operation.
FIRE ASSAY The assaying of metallic ores, usually gold and silver, by methods requiring furnace heat. (Fay) Fire assaying, in essence, is a miniature smelting process which recovers and reports the total gold content of the assay sample, including gold combined with other elements, or mechanically locked in the ore particles. Consequently, the gold value indicated by fire assay is not necessarily recoverable by placer methods. For this and other reaons, the gold content of placer material is not normally determined by fire assay. See - Free gold assay.
FLAKY GOLD Very thin scales or pieces of gold.
FLASK The unit of measurement for buying and selling mercury (quicksilver). A standard iron flask contains 76 pounds of mercury.
FLAT An essentially level gravel bar or deposit along the banks of a river. FLOAT. A term much used among miners and geologists for pieces of ore or rock which have fallen from veins or strata, or have been separated from the parent vein or strata by weathering agencies. Not usually applied to stream gravels. (Fay)
FLOAT-GOLD Flour gold. Particles of gold so small and thin ihat they float on and are liable to be carried off by the water. (Fay) See - Flood gold.
FLOOD GOLD Fine-size gold flakes carried or redistributed by flood waters and deposited on gravel bars as the flood waters recede. Flood gold sometimes forms superficial concentrations near the upstream end of accretion bars. See - Float gold.
FLOOD PLAIN That portion of a river valley, adjacent to the river channel, which is built of sediments during the present regimen of the stream and which is covered with water when the river overflows its banks at flood stages. (AGI)
FLOTATION The minimum working draft of a dredge. When a dredge "digs flotation" it excavates the ground to the minimum depth required for floating the dredge. This is usually done when passing through tailings or moving between nearby working areas.
FLOUR GOLD The finest gold dust, much of which will float on water. (Fay) Flour gold, such as that found along the Snake River in Idaho, commonly runs 3 million colors to the ounce.
FLOURED MERCURY (QUICKSILVER) The finely granulated condition of quicksilver, produced to a greater or less extent by its agitation during the amalgamation process. The coating of quicksilver with what appears to be a thin film of some sulphide, so that when it is separated into globules these refuse to reunite. Also called Sickening and Flouring. (Fay)
FLUVIAL Of, or pertaining to rivers; produced by river action, as a fluvial plain. (Fay)
FLUVIATILE Caused or produced by the action of a river; fluvial. (Fay) FLUVIOGLACIAL. Produced by streams which have their source in glacial ice. (Fay) See - Glaciofluvial.
FLUVIO-MARINE Formed by the joint action of a river and the sea, as in the deposits at the mouths of rivers. (Fay)
FOOL'S GOLD A substance which superficially resembles gold; usually pyrite, a sulphide of iron, FeS2.
FREE GOLD Gold uncombined with other substances. Placer gold. (Fay) FREE GOLD ASSAY. A procedure carried out to determine the free gold content of an ore. In the case of placer material; a procedure to determine the amount of gold recoverable by gravity concentration and amalgamation.
FREE-WASH GRAVEL Gravel that readily disintegrates and washes in a sluice. Loose, clay-free gravels such as those found in accretion bars are generally free-wash gravels.
GIANT See - Hydraulic giant; also Intelligiant.
GLACIAL Pertaining to, characteristic of, produced or deposited by, or derived from a glacier, (AGI)
GLACIOFLUVIAL Of, pertaining to, produced by, or resulting from combined glacier action and river action. (Fay) See - Fluvioglacial.
GOLD DUST A term once commonly applied to placer gold, particularly gold in the form of small colors.
GOLD PAN See - pan.
GOLD-SAVING TABLE The sluices used aboard a dredge are customarily called gold-saving tables, rather than sluice boxes.
GRADE 1. The amount of fall or inclination from the horizontal in ditches, flumes, or sluices; usually measured in inches fall per foot of length or inches fall per section of sluice. 2. The slope of a land or bedrock surface; usually measured in percent. A one percent grade is equivalent to a rise or fall of one foot per hundred. 3. The slope of a stream, or the surface over which the water flows; usually measured in feet per mile. Streams having a grade of about 30 feet per mile favor the accumulation of placers, particularly where a fair balance between transportation and deposition is maintained for a long time. 4. The relative value or tenor of an ore, or of a mineral product.
GRADED STREAM A stream in equilibrium, that is, a stream or a section of a stream that is essentially neither cutting or filling its channel.
GRAIN A unit of weight equal to 0.0648 part of a gram, 0.04167 part of a pennyweight, or 0.002083 part of a troy ounce. There are 480 grains in a troy ounce. A grain of fine gold has a value of 7.29 cents (@$35/oz.).
GRAM A unit of weight in the metric system equal to 15.432 grains, 0.643 pennyweight, or 0.03215 troy ounce. There are 31.003 grams in a troy ounce. A gram of fine gold has a value of $1.12 (@$35/oz.).
GRAVEL A comprehensive term applied to the water-worn mass of detrital material making up a placer deposit. Placer gravels are sometimes arbitrarily described as "fine" gravel, "heavy" (large) gravel, "boulder" gravel, etc.
GRAVEL MINE A placer mine; a body of sand or gTavel containing particles of gold. (Fay)
GRAVEL-PLAIN PLACERS Placers found in gravel plains formed where a river canyon flattens and widens or more often, where it enters a wide, low-gradient valley.
GRIZZLY An iron grating which serves as a heavy-duty screen to prevent large rocks or boulders from entering a sluice or other recovery equipment.
GROUND SLUCING A mining method in which the gravel is excavated by water not under pressure. A natural or artificial water channel is used to start the operation and while a stream of water is directed through the channel or cut, the adjacent gravel banks are brought down by picking at the base of the bank and by directing the water flow as to undercut the bank and aid in its caving. Sluice boxes mayor may not be used. Where not used, the gold is allowed to accumulate on the bedrock awaiting subsequent clean-up. A substantial water flow and adequate bedrock grade are necessary. See - Booming.
GUTTER The lowest portion of an alluvial deposit; commonly a relatively narrow depression or trough in the bedrock. In some placers the pay streak is largely confined to a narrow streak or "gutter".
HAND DRILL See - Ward drill. Also see - Banka drill and Empire drill.
HEAD 1. A measure of (water) pressure. 2. The height of a column of water used for hydraulicking. For example, a hydraulic mine in which the point of water discharge is 200 vertical feet below the intake point (of the pipe) would be said to be working with a 200-foot head.
HEAVY GOLD 1. Gold in compact pieces that appear to weigh heavy in proportion to their size. 2. Rounded, "shotty" or "nuggety" gold.
HEAVY MINERALS The accessory detrital minerals of a sedimentary rock, of high specific gravity. (AGI) The black sand concentrate common to placers, would more properly be called a 'heavy-mineral' concentrate.
HIGH-GRADE 1. Rich ore. 2. To steal or pilfer ore or gold, as from a mine by a miner. (Fay)
HIGH-GRADER One who steals and sells, or otherwise disposes of high-grade or specimen ores. (Fay)
HIGH TENSION SEPARATOR A machine, essentially consisting of a rotating drum, upon which a thin layer of dry sand or mineral grains are fed, and an electrode suspended above the rotating drum, or rotor. The electrode furnishes a high voltage discharge at high current flow. High tension separators employ a high rate of electrical discharge to separate various minerals according to their relative conductivity. Some are pinned to the rotor while others are attracted toward the electrode, with a resultant "lifting" effect. The pinning and lifting effects, imparted in varying degrees to different minerals, flattens or heightens their respective trajectories as they leave the rotor. Adjustable splitters placed in the trajectory are employed to cut selected minerals or groups of minerals from the thus stratified stream of material. High tension separators differ from electrostatic separators in that the latter employ charged fields with little or no current flow. High tension separators are extensively used for separating heavy minerals recovered from beach sands, monazite placers, etc.
HILLSIDE PLACERS A group of gravel deposits intermediate between the creek and bench placers. Their bedrock is slightly above the creek bed, and the surface topography shows no indication of benching. (Brooks)
HORN SPOON See - spoon.
HUMPHRYS SPIRAL See - Spiral concentrator.
HYDRAULIC DREDGE A dredge in which the material to be processed is excavated and elevated from the bottom of a stream or pond by means of a pump or a water-powered ejector. Large hydraulic dredges may be equipped with a digging ladder which carries the suction pipe and a motor-driven cutter head, arranged to chop-up or otherwise loosen material directly in front of the intake pipe. Dredges having this configuration employ a deck-mounted suction pump and they may carry the mineral recovery equipment on board the dredge or more commoly, they may transport the excavated material, by means of a pipe line, to a recovery plant mounted on independent barges or on the shore. See - Jet dredge; also bucket-line dredge.
HYDRAULIC ELEVATOR A near-vertical pipe employed in hydraulic mining to raise excavated material from the working place to an elevated sluice, or to a disposal area, by means of a high-pressure water jet inducing a strong upward current in the elevator pipe. see - Rubel elevator.
HYDRAULIC GIANT The nozzle assembly used in hydraulic mining. The giant is provided with a swivel enabling it to be swung in a horizontal plane, and it may be elevated or depressed in a vertical plane. Nozzle sizes range from 1 to 10 inches in diameter and the largers sizes are provided with a deflector, enabling them to be moved with little effort. In California, giants discharging as much as 15,000 gallons per minute in a single stream at a nozzle pressure of over 200 pounds per square inch, have been used. The giant is also known as a "Monitor". Both terms stem from manufacturer's trade names. See - Intelligiant.
HYDRAULIC MINING A method of mining in which a bank of gold-bearing earth or gravel is washed away by a powerful jet of water and carried into sluices, where the gold separates from the earth by its specific gravity. (Fay)
HYDRAULIC MONITOR See - Hydraulic giant.
HYDRAULICKING Mining by the hydraulic method. Note spelling.
INCHES OF WATER A common expression denoting the quantity of water (in miners' inches) available or being used in a placer operation. See - Miners' inch.
INDICATED VALUE The value of a placer sample, derived by formula, before making adjustments to compensate for excess or deficient core rise, in the case of churn drilling; or before applying shaft factors, boulder factors, or other empirical corrections. See - Adjusted value.
INLET The point where a channel is cut off by a ravine or canyon on the upstream end. (Dunn, R.L.) Usually applied to buried Teritary channels. Compare with Breakout; and with Outlet.
INTELLIGIANT The trade name for a hydraulic giant that is provided with water-powered piston and cylinder arrangements to control its vertical and horizontal traverses. Some models can be rigged for automatic operation and can run unattended in a preset arc or pattern. See - Hydraulic giant.
IRON SAND 1. Magnetite or ilmenite-rich sand. 2. Black sand concentrate containing an abundance of magnetite.
JET DREDGE A form of hydraulic dredge. Jet dredging equipment may range from a simple, self-contained pipe-like venturi containing riffles, that is carried by a diver and operates entirely underwater to larger and more elaborate surface units carried on inflated rubber tubes or styrofoam floats. These devices, operated by one or two men, are similar in two ways: 1. They rely on a water jet and venturi effect to pick up unconsolidated stream-bottom materials and carry them to a gold recovery device, usually riffles. 2. The suction intake is normally hand-held and is guided by a diver working on the stream bottom. The typical jet "dredge" entails a small or modest capital outlay and is typically used for recreation-type mining. See - Hydraulic dredge.
JET DRILL A churn-type drill employing a string of reciprocal hollow rods equipped with a drill bit. Water is pumped through the rods and discharged through an orifice near the bit. Cuttings resulting from the chopping action of the bit are carried to the surface by wash water rising between the drill rods and casing. Rods are added as the hole deepens, thus the drill cable does not go down the hole as would be the case in conventional churn drilling. Jet drills are well suited to sampling low-value minerals, such as ilmenite, occurring in beach deposits.
JIG A machine in which heavy minerals are separated from sand or gangue minerals on a screen in water, by imparting a reciprocating motion to the screen or by the pulsation of water through the screen. Where the heavy mineral is larger than the screen openings, a concentrate bed will form on top of the screen. Where the heavy mineral particles are smaller than the screen openings, a fine-size concentrate will be collected in a hutch beneath the screen.
KEYSTONE CONSTANT See - Radford factor. KEYSTONE DRILL. See -Churn drill. KNUDSEN BOWL. See - Ainlay bowl.
LACUSTRINE DEPOSITS Deposits formed in the bottom of lakes. (Fay) Compare with Lake-bed placers.
LAKE-BED PLACERS Placers accumulated in the beds of present or ancient lakes that were generally formed by landslides or glacial damming. (Brooks) It should be noted that a lake-bed (or lake-bottom) placer might actually be a drowned stream placer,
LAVA The term 'Lava' as used by a placer miner, may designate any solidified volcanic rock including volcanic agglomerates.
LEAD (pronounced leed) Deeply buried placer gravel, where rich enough to work, and particularly when in a well-defined bed, is often termed the "lead" or, "pay lead".
LIGHT GOLD Gold that is in very thin scales or flakes or in pieces that look large as compared to their weight. See - Flood gold.
LITTORAL Pertaining to the shore of a lake, sea, or ocean.
LONG TOM 1. A small, sluice-type gold washer widely used in California during the 1850's and 60's. The early long tom was built in two sections; a washing box equipped with a perforated plate to screen out the rocks; followed by a short sluice containing riffles. 2. A short auxiliary sluice used aboard a dredge to further reduce concentrate taken from the dredge riffles at clean-up time. 3. A short sluice used to wash placer samples.
LOW-GRADE A term applied to ores relatively poor in the metal for which they are mined; lean ore. (Fay)
MAGNETIC SEPARATOR A device in which a strong magnetic field is employed to remove magnetic materials from a sand or a concentrate, or to selectively remove or separate their constituent minerals. Magnetic separators are commonly used in conjuction with high tension separators to process the heavy mineral concentrates obtained from beach sands, monazite placers, tin placers, etc.
MARINE MINING The exploitation of sea-bottom mineral deposits, including placers. See - Marine placer.
MARINE PLACER A deposit of placer-type minerals on the ocean or sea bottom beyond the low-tide line, as distinguished from beach placers. Some marine placers may contain material related to beach deposits formed during periods of low sea level. Others may contain stream-type placers or mineral concentrations formed on land and later drowned by a lowering of the coastal region.
MATURITY (MATURE VALLEY) See - Erosion cycles.
MEANDER One of a series of somewhat regular and looplike bends in the course of a stream, developed when the stream is flowing at grade, through lateral shifting of its course toward the convex sides of the original curves. (Fay)
MEDIUM-SIZE GOLD Gold of an approximate size that will pass through a 10-mesh screen and remain on a 20-mesh screen. Compare with Coarse gold; also Fine gold.
MERCURY A heavy, silver-white liquid metallic element, useful in placer mining where its chemical affinity for gold is taken advantage of to help detain gold in a sluice box. Mercury placed in the riffles forms a gold amalgam which is removed at the time of clean-up and then retorted to recover the gold. The miners' term for mercury is "Quicksilver" or simply, "Quick". Symbol, Hg; specific gravity, 13.54.
MILLIGRAM The one-thousandth part of a gram. As a matter of convenience, the milligram is widely used as the unit for reporting gold weights in placer samples. There are 31,103 milligrams in a troy ounce. With gold at $35 per troy ounce, 1 milligram of fine gold is worth 0.112 cent and 1 milligram of ordinary placer gold is worth about 0.1 cent, or in other words, 10 milligrams to the cent.
MINERS' INCH A unit of water measurement. Originally it represented the quantity of water that will escape from an aperture one inch square through a two-inch plank, with a steady flow of water standing six inches above the top of the escape aperture. The miners' inch is now defined by statute in various states.
1 second-foot = 40 miners' inches in Arizona, California, Montana and Oregon.
= 50 miners' inches in Idaho, Nevada, New Mexico and Utah.
= 38.4 miners' inches in Colorado.
1 miners' inch equals 11.25 gallons per minute when equivalent to 1/40 second-foot.
1 miners' inch eauals 9 gallons per minute when equivalent to 1/50 second-foot.
MINERS' PAN
MINING CLAIM That portion of the public mineral lands which a miner, for mining purposes, takes and holds in accordance with the mining laws. (Fay) A mining claim may be validly located and held only after the discovery of a valuable mineral deposit. See - Discovery.
MONAZITE A phosphate of the cerium metals (cerium, didymium, lanthanum) and other rare-earth metals. Monazite-bearing alluviums have been mined for their thorium content (by dredging) in Idaho and elsewhere.
MONITOR See - Hydraulic giant.
MORAINE An accumulation of earth, stones, boulders, etc., carried and finally deposited by a glacier. A Moraine formed at the lower extremity of a glacier is called a TERMINAL Moraine; at the side, a LATERAL Moraine; in the center and parallel with its sides, a MEDIAL Moraine and beneath the ice but back from its end or edge, A GROUND Moraine. (Fay) Placer gold is found in some glacial Moraines and deposits of reworked Morainal material, that is, material reworked by streams; some have been dredged and worked by other placer methods.
MOSS MINING (Mossing). The gathering of moss from the banks of gold-bearing streams for the purpose of burning or washing it, to recover its gold content. Under certain conditions, moss or similar vegetation will capture and hold small particles of gold being carried downstream by flood waters. See - Flood gold.
MUCK (Alaska) A permanently frozen overburden overlying placer gravels in the interior of Alaska. It is composed of fine mud, organic matter and small amounts of volcanic ash. It varies in depth (thickness) from seldom less than 10 feet to 100 feet or more in places. This overburden (muck) must be removed and the underlying gravels thawed before dredging is possible.
NATIVE GOLDM 1. Metallic gold found naturally in that state. 2. Placer gold.
NUGGET 1. A water-worn piece of native gold. The term is restricted to pieces of some size, not mere 'colors' or minute particles. Fragments and lumps of vein gold are not called 'nuggets', for the idea of alluvial origin is implicit. (Fay) 2. Anything larger than, say, one penny-weight or one gram may be considered a nugget. See - Pepita.
NUGGETY Like or resembling a nugget; occurring in nuggets; also abounding in nuggets. (Fay)
