Death Valley
Historic Resource Study
A History of Mining
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ADIT: A horizontal passage into a hillside

AERIAL TRAMWAY: transports loads in carries suspended from cables stretched between two points, often far apart. On continuous tramways a series of loaded carries travel in one direction while empty carriers return in another. A reversible tramway supports one carrier that travels back and forth on the same cable.

AMALGAM: gold or silver combined with mercury.

ARRASTRA: a primitive ore mill whose design was brought to this country by the Spaniards. Considered especially useful because it could be built anywhere from materials at hand, it consisted of a circular trough constructed of smooth, hand, flat-surfaced stones set in clay and averaging about two feet deep and six across, although the size varied according to the amount of area available. A low stone coping followed around the periphery of the trough. In the center of the structure was a pole that pivoted and dragged two large, flat stones around the trough to crush the ore. This pole was powered by horse, mule, water, hand, or steam or gasoline engine

The floor of the arrastra was then covered with one to two inches of broken ore to which water was periodically added. The stones were dragged around until the gold ore was pulverized to a sand, freeing the gold, a period of usually one to two days. The muddy, slimy mixture was then flushed out down a sort of flume and sometimes quicksilver or mercury amalgamated with the gold or silver in catch basins. The amalgam was then distilled and the small gold particles separated and recovered. Any material caught in between the floor stones could be scooped up with a small horn spoon and panned. Before abandoning the arrastra, its floor stones were pulled up and any ore caught there removed. Sometimes a higher percentage of gold could be gained in this fashion than from a small stamp mill, although the latter was more economical where large tonnages of ore were concerned. The arrastra could only be used with free-milling ore

ASSAY: chemical or physical method of ascertaining the commercial value of ore.

ASSESSMENT WORK: the locators of unpatented placer and lode claims were required by law to perform $100 (in value) worth of labor and improvements per claim annually in order to prevent relocation of their claim by others.

BALL MILL: a cylindrical or conical container, resting on supports, that is used for coarse primary grinding. Its diameter approximately equals its length. It functions by rotating horizontally while iron or steel balls roll over the ore. These balls may be up to five inches in diameter, but smaller ones are used for finer grinding. In this latter case the mills are longer.

BOND-AND-LEASE SYSTEM: an arrangement that evolved circa the 1890s to protect buyers from salted mines. A prospective purchaser posted bond in the amount of the selling price of a mine, then took possession and carried out development work. The proceeds from all pay ore were his. At the expiration of the lease period, if the mine was still producing, the purchaser could exercise his option and buy the property, with the bond money going to the owner. If the lessee thought the prospect had no future, be returned it to the vendor along with any development installations and reclaimed his bond. In a leasing situation where no bond has been put up, the vendor can refuse to renew a lease on a profitable mine after the leasing period is up. In this way the owner of a mine who does not have time to work it himself can get the necessary development work started and increase the assets of his holdings.

CLAIM: a parcel of land legally held for mining purposes, the location of which is recorded with the county and marked by monuments.

COLLAR: top of a shaft.

CONCENTRATOR: plant where ore is separated into valuable and rejected materials.

CROSSCUT: horizontal opening driven across a vein or across the direction of the main workings. The connection from a shaft to a vein.

CRUSHERS: an apparatus that grinds ores without water and is designed to produce feed for the grinding mills. Common types used are jaw and gyratory crushers (breakers) and reduction gyratories, cone crushers, and rolls (intermediate crushers). The best-known type of jaw crusher is the Blake, with a movable jaw pivoted at the top.

CUSTOM ORE MILL: a mill designed to treat for a fee small lots of ore from prospects or mines not equipped with reduction facilities. An important factor in the early economic development of a mineral area.

CYANIDE PROCESS: a chemical operation for extracting gold from finely-crushed ores, concentrates, and tailings by application of cyanide of potassium. The ore is first crushed to one-inch size and then conveyed to a set of rollers for grinding to the required fineness. It is then put in circular tanks, about twenty feet in diameter. About eight inches above the base are false bottoms of wood slats over which a canvas is laid to act as a filter. The ore was spread on top of the canvas and a cyanide solution applied from the bottom of the tanks, which worked on the ore until the gold was dissolved. The solution was then drawn off and sent to a tank where it was precipitated. The precipitates were melted in a furnace and poured into molds. Success of this process depended on the amount of tonnage (it could be costly) and the composition of the ore. It was widely used in the 1930s to rework old mine dumps because of its simplicity and the fact that larger percentages of gold could be recovered from the ore.

DRIFT: horizontal underground passage driven along an ore structure such as a vein.

DUMP: a pile or heap of waste rock material or other non-ore refuse excavated in driving a tunnel or shaft and located near a mine.

EXPLORATION: actions such as drilling, trenching, or excavating underground openings to ascertain the size, shape and location of an ore body. Next step after area has been prospected.

FLOTATION: a method of mineral separation akin to concentration. Crushed, ground, and classified ore is pulped with water, while special reagents are used to make one or more of the ore minerals water-repellant and responsive to attachment with air bubbles, As the desired minerals float to the surface attached to the bubbles they are removed by mechanical paddles as concentrate, leaving the other mineral to sink. Often several stages of flotation with selective reagents are used to obtain the desired concentration.

FLUX: a substance promoting the fusion of minerals or metals.

HANGING WALL: the layer of rock or wall overhinging a lode, on the upper side of an inclined vein.

HEADFRAME: the steel or timber frame at the top of a shaft, carrying a sheave or pulley for hoisting the rope. Its height depends on the method of disposing of the rock and the size of the ore bucket. It is used for development work and shaft sinking. Most were usually constructed of wood because it was less expensive, readily obtained, and quickly erected.

HIGH-GRADE: rich or shipping ore.

INCLINED SHAFT: refers to openings inclined from the vertical to 45 degrees or less.

LEACHING: a solution-mining technique for extracting soluble ores in situations where conventional mining methods are not economical, Heap leaching is performed where the grade of ore is too low to pay for haulage or to be treated by conventional concentration or by leaching in vats, It is also used for complex ores that cannot be economically treated by conventional processes.

LEDGE: mass of rock constituting a valuable mineral deposit.

LEVEL: horizontal passages or drifts spaced at regular intervals in depth and either numbered from the surface in regular order or designated by their actual elevation below the top of the shaft.

LODE: several veins found close together enabling them and intervening rock to be worked as a unit. Generally interchangeable with vein; a well-defined occurrence 01 valuable mineral-bearing material. A lode claim is staked on veins or lodes of quartz-bearing gold or silver and composed of twenty acres. Lode gold is that in place within solid rock where it has been deposited.

MILL: reducing plant where ore is concentrated and/or metals recovered.

MILL-SITE: a five-acre claim of non-mineral land. May be contiguous or not to claim producing ore for the mill. Must be used for mining and milling purposes in order to retain title.

MINING DISTRICT: section of country designated by name, having described boundaries within which minerals are found and worked under the rules and regulations prescribed by miners therein.

OPEN-PIT OPERATIONS: a method of mining an ore body by stripping away the overburden and reaching the ore from above. It requires a large area for mining, stripping, disposal of waste rock, placement of lowgrade stockpiles or heap-leaching operations, construction of roads, etc. A complex and costly operation.

ORE: mineral sufficient in quality to be exploited at a profit.

ORE BODY: solid and fairly continuous ore mass that may include low-grade ore and waste plus pay ore

ORE CARS: in Western mines horizontal tramming was done basically with one-ton iron ore cars equipped with four closely-set flanged wheels running on an eighteen or twenty-inch gouge track. The body was so suspended that on tripping a latch lever they dumped sideways; many, however, had center pintles, enabling the box to be swung ninety degrees and dumped end over. One loaded car was all a man could push, but mules could pull trains of up to ten cars linked together with short chains. In larger, busier mines the tram system included turnouts and junctions that were directed by hand-operated track switches, and steam, gasoline or electric engines.

PLACERS: superficial deposits, occupying ancient river beds, that have washed down from a vein or lode, or deposits of valuable minerals found in the alluvium of active streambeds. Placer mining involves the recovery of this gold from the sands and gravel of a streambed and is one of the oldest forms of mining. Potentially rich spots are washed with a pan, long tom, and sluice. Gold, particularly, is found in this situation because it is heavy and resists corrosion. Placer claims are limited to twenty acres.

POCKET: rich spot in vein or deposit.

PORTAL: mouth of adit opening.

PROSPECTING: involves ground reconnaissance and preliminary observation. Prospectors could rarely afford to explore their own prospects to any extent, so they tried to interest a well-financed miring organization in carrying out further exploration.

QUARTZ MINE: area in which ore deposits are found in veins or fissures in the rocks of the earths crust. Usually applied to lode gold mines.

RAISE: vertical or inclined opening driven upward from adit level to connect with level above or to explore ground above for limited distance.

SHAFT: vertical or steeply inclined opening excavated from surface.

STAMP MILL: apparatus that crushes rock by descending pestles or stamps operated by water, steam, electricity, or gasoline power.

STOPE: underground excavation from which ore has been or is being extracted. The particular methods used are dependent on the size and shape of the ore body, overburden conditions, etc.

open stoping--small ore bodies are mined completely out with no pillar of ore left in place to support the walls.

room and pillar--pillars left in regular pattern while rooms are mined out. At the end of the operation they are robbed just before that portion of the mine is abandoned. The stope walls will then collapse.

STRIKE: to find an ore vein; a valuable discovery.

TAILINGS: refuse material resulting from the washing, concentration, or treatment of ground ore; material too poor to be treated further. The waste from the concentration process is disposed of as mill tailings that are directed through ditches, pipe systems, etc., to pond disposal areas downhill from the mill. Mill tailing ponds were usually impounded behind embankments built from the tailing material itself. In the ponds the solids separate from the liquid and are deposited on the pond floor, while the water eventually soaks into the ground or is drained off.

TRAMMING: removal of muck into wheelbarrows or mine cars to the surface.

TUNNELS: horizontal or nearly so underground opening from one side of mountain to another. Sometimes wrongly used synonymous with adit or drift.

VEIN: zone or belt of mineralized rock lying within boundaries clearly separating it from neighboring rock.

WASTE ROCK: barren or low-grade material taken from mine during exploration and development.

WINZE: subsidiary shaft starting underground, usually connection between two levels. Work down from an adit level, as opposed to a raise.1

1. The above has drawn on the following sources: Inyo Independent 23 July, 20 August, 1937; Stanley W. Paher, Death Valley Ghost Towns (Las Vegas: 1973); Otis E. Young, Jr., Western Mining: An Informal Account of Precious-Metals Prospecting Placering Lode Mining, and Milling on the American Frontier from Spanish Times to 1893 (Norman: Univ. of Oklahoma Press, 1970); Otis E. Young, Jr., Black Powder and Hand Steel: Miners and Machines on the Old Western Frontier (Norman: Univ. of Oklahoma Press, 1976); Works Progress Administration, Death Valley: A Guide (Boston, 1939); Robert Peele and John A. Church, eds., Mining Engineers Handbook 3d ed., 2 vols. (New York: John Wiley & Sons, Inc., 1941); "Prospecting for gold in the United States," pamphlet of USGS, Inf-67-9, Washington, USGPO; Engineering and Mining Journal 11 February 893; "Anatomy of a Mine--from Prospect to Production," published by U.S. Forest Service, Intermountain Region, as part of SEAM program; Rodman Wilson Paul, Mining Frontiers of the Far West, 1848-1880 (New York: Holt, Rinehart and Winston, 1963).

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Last Updated: 22-Dec-2003