U.S. Department of the Interior, National Park Service
Survey and Documentation
Perhaps most importantly, surveys of historic mining areas should be conducted with caution. Because mining properties are often located in remote areas, such as rugged mountain slopes or in steeply banked canyons, hiking trails may provide the only access. Given this situation, those involved with mining area surveys should be prepared to encounter rigorous conditions when conducting fieldwork.
Mines present special hazards with potentially lethal consequences. Field personnel should be trained in, familiar with, and able to recognize mining-related dangers prior to conducting field work. All explosives encountered should be considered extremely dangerous. Blasting caps are just as dangerous as "stick" powder. Explosives can be found in any part of a mining area, not just in the vicinity of the powder magazine. The ground around mine openings is frequently unstable; unguarded and obscured shafts, raises, and stope openings are hazards to avoid. Covered mine openings should not be considered safe. Unless proper training has been completed, one should not enter the underground portion of a mine. The hazards associated with surveying historic mines are real and should not be ignored.
In the West, many historic mines are located on public lands. The opposite situation prevails in the East where most historic mines will be on privately owned lands. Regardless of the geographic locale, owner consent should always be obtained before venturing onto privately-owned mine lands.
After ascertaining that conditions are safe and contacting the owners, begin the survey by defining the limits of the area to be investigated. This could be the entire mining district or just one mining claim whose boundaries are recorded in the miningdeed records in the county courthouse or in the mineral patent records of BLM. If a mine operation extended over several claims, patented or unpatented, the survey area should encompass the full extent of claims associated with the mine. In the case of large mining corporations, ownership could extend over hundreds of claims. Other sources that will assist in defining the limits of a survey area include oral histories, company records, industrial directories, and USGS and State geologic maps and surveys.
The relationship between the claims and the topography can differ dramatically between hard rock and placer mining districts. Placer claims will usually be oriented to the drainage patterns while lode claims will follow the geologic structure as it was understood at the time the claims were located. Claims may also overlap and homestead, townsite, and other land claims may cover the same ground as placer and lode mineral claims. Knowledge of the historic development of an area should be acquired before conducting field work. This will ensure appropriate boundaries for the field survey.
Because many mining properties contain few standing buildings or structures and disconnected parts of machinery scattered throughout the area, the field surveyor should use the previously gathered historic context information to determine the type of mine at hand. This step is important because, for example, a placer mine will have different features than a hard rock mine or mill. Hard rock mines tend to have more fixed structures than placer mines. More important, placer mine surface equipment does not necessarily stay in one place. Over time, placer mine excavation and processing plants are moved along a creek as the stream bed is dug up and the auriferous material washed through the sluice box. On some creeks, the equipment associated with a placer mine may be found abandoned in place miles from where it was first used.
Furthermore, the fieldwork should result in thorough mapping of any evidence of earth-moving activity. This would include the mapping of waste rock and tailings piles. Dumps and tailing piles will often indicate the locations of removed or obscured features and will provide clues about the type of activity that created them. Coal mine waste gobpiles on the Illinois prairie or placer mine dredge tailings in California may be the only indications that major mining industries once operated in these areas.
Outlying support features should be mapped as well. For example, if a headframe stands over a shaft, not only should the headframe be described, but also the hoist house. The dams, flumes, and penstock supplying water to placer mines are as important as the camps erected to house the miners. Machinery should be described, especially its function and manufacturer (if these can be readily determined). Sanborn fire insurance maps and patent maps from BLM may provide descriptions and details on mines and structures that date to the time when the mine was in operation, as would any map prepared by companies owning the property. If available, these maps should be compared to the resources evident today.
Mill drawings may be available from company records. If not, examples of mills are in standard plan books, mine machinery catalogs, contemporary mine engineering books, or advertisements in such journals as Coal Age, Mining and Scientific Press, The Colliery Engineer and Engineering and Mining Journal. Regional journals are also helpful, but are rare until the 1890s. Field analysis of mills, especially outlines of foundations and tailings, will help describe the adaptations of general plans for the specific location.
A process flow chart is essential in understanding the metallurgy in use at mills. Flow charts were prepared for all mills, but few are extant. Thus, thorough mapping and noting of machinery in place is needed in order to reconstruct the flow chart diagram. Similarly, mapping of landscape features and remaining equipment can be used to reconstruct operations at placer, hard rock, and coal mines. While usually less complex, flow charts at coal and placer mines are equally useful to the understanding of mining operations.
Mining property surveys should include preliminary research related to the mine, the actual field survey of physical remains, and property analysis designed to reanimate the operational system which once functioned at a mine. This three step process is especially important in cases where the contemporary mining property lacks historic buildings and structures.
As discussed previously, preliminary research is begun during the initial process of preparing historic contexts. However, in most cases, new information will be produced to refine historic contexts both immediately before and during the field survey. Thus, the ongoing nature of preliminary research will help to flesh out the historic contexts, develop new contexts, and provide further input to the field survey process. In turn, information derived from the survey will lead to further refinements in the historic contexts.
When conducting preliminary research, it is critical to engage in a literature search that yields information about the type of extraction, beneficiation, or refining process that took place in a given area. Preliminary research into the history of resources associated with mining activity plays an important role in preventing erroneous field interpretations: bituminous coal is processed differently than anthracite; a gold mill is different than a silver mill. At minimum, read the USGS or State geological bureau report on the mining area prior to beginning field work. Remember too that technology changed as did the terms used to describe mining. Use technical publications contemporaneous with the period of mine operation: a 1930s technical description of a gold mill will differ greatly from a description in an 1880s publication.
Other sources to consult include the following: census records, tax assessment records, company books, personal diaries, community plats, cartographic sources, iconographic and pictorial materials, professional and technical journals, governmental publications, newspaper accounts, city directories, oral histories, and local informants. Information recorded during field work should use mining nomenclature from the period of operation and for the region. A West Virginia coal tipple and a Nevada mine headframe and ore bin might do essentially the same thing store coal or ore pulled from the mine but mining glossaries will help field crews get their descriptions correct. Use the appropriate glossaries and technical publications for the area and era. (See Section VII for a partial glossary of mining terms.) Initial historic contexts developed at this point should remain flexible enough to allow for the incorporation of new materials that may result from visiting the property or completing additional research.
With the preliminary research documentation in hand, the field inventory of physical remains can begin. The physical remains of mines may include standing buildings, structures, and other architectural remains; machinery; archeological remains; and landscape features such as mine waste rock dumps, mill tailings, water delivery systems, open pits, and roads. Archeological remains, which may be the most abundant, typically include prospects, privy pits, wells, cellar holes, building foundations and platforms, dugouts, domestic and industrial trash dumps, isolated artifacts, collapsed headframes, machine pads and platforms, depressions, roads, ditches, pathways, and bulldozer cuts.
The methods used to locate the physical remains of mines may include aerial photography, pedestrian survey, remote sensing (such as radar profiling or proton magnetometry), and simple probes. For preliminary mapping and assessment purposes, low-level aerial photography is an excellent way to document the physical remains of mining properties. A systematic program of pedestrian survey, however, is essential. Planning for scale is critical since the physical remains of mining properties may cover a large geographical area. Historic placers, which can extend for miles, call for inventive approaches to field mapping and documentation. For example, using small-scale aerial photography and transparent overlays to record linear features and apparently isolated elements as well as the location of larger concentrations of features can often make sense out of apparent chaos. Superimposed historic maps on contemporary maps can help identify features and further detail the chronological and industrial development of an area. Recording methods should include photography, the preparation of architectural plans and elevations, sketches of machinery and other objects, narrative description, and the preparation of scaled maps.
Field surveys also should include methods for assessing the integrity and significance of the physical remains. Determining whether archeological deposits have a buried component may, for example, require probing or remote sensing. The suitability of the physical remains for conveying a sense of time, place, and historical patterns or themes should be considered. The surveyor should also record observations about the extent to which the physical remains are repositories of information, including the presence or absence of artifacts that carry information needed to answer important research questions about mining technology or community. Mining resource surveys will often require multi-disciplinary approaches to survey, using the talents of archeologists, historians of technology, landscape architects, architects, and mining engineers as well as assistance from geologists or practicing miners or individuals with first hand knowledge of the area.
Beyond field identification of individual physical remains, the greatest challenge connected with mining property inventories involves the issue of property analysis. In this case, property analysis refers to the need to link the now disparate physical remains to the former reality of working mines and related social systems. What now appears to be disconnected and geographically isolated buildings, landforms, machinery, and archeological features once worked together to accomplish ore extraction or beneficiation.
Identifying the activities and the time periods represented by the physical remains is a key problem. Abandoned mining properties, for example, typically are reoccupied and may include buildings, machinery, landforms, and archeological remains from more than one time period. The new episodes of mining cut through the physical remains of older mining activities, making it difficult to interpret the engineering and other technological systems from earlier time periods. Sorting the physical remains by time period and activity into separate technological or social systems may be helpful. The location of the Tenabo Mill in central Nevada, for example, which was built in 1886 to process gold and silver ore, includes the mostly archeological remains of two separate beneficiation technologies: the Russell process in the original mill and the cyanide process installed in 1908. Evidence of both technological systems can be seen when viewing the extant physical remains today, but the earlier Russell process technology has been largely destroyed by the later cyanide operation (Hardesty, 1988).
Identifying Property Types
Mining properties may contain a great variety of resources representing the mineral-extraction process. Evaluation of these complex properties can be organized by noting that the processing of ore into metal includes the following three basic functions: extraction of the ore from the earth; beneficiation, which upgrades the ore's value; and refining, which enhances the value of the ore/metal even further until it achieves a nearly pure state.
All three functions may occur within one mining property, such as at some Western or southern Appalachian gold mines, or may be miles apart, such as iron, copper, or lead smelters located great distances from mines. Although a universal description of mineral properties will not address all individual cases, the following provides a general guide to defining historic mining property types based on these three fundamental stages of mineral processing:
The property types associated with mine extraction sites can be generally classified into two categories reflecting the evolution of a mine: prospecting/mine exploration property types and mine development or exploitation property types. The distinction can be applied to hard rock, placer, and coal mines.
Prospecting/Mine Exploration Property Types
These property types are associated with the search for ore bodies. Hand-dug prospect pits, power-shovel trenches, bulldozer cuts, and drill holes, for example, are the physical remains associated with four different patterns of mine exploration technology. Some additional explanation will help to understand the origin of typical exploration activity.
Mining is a speculative industry. To discover metal, many test pits or prospects must be dug. According to the 1872 Mining Law, holding an unpatented claim requires a miner to do annual assessment work that might include digging another prospect hole in order to retain possessory title by demonstrating that a claim is still active. If a mining district has a producing mine, speculators employ a process sometimes known as grubstaking that involves paying prospectors to seek outcrops of ore and to excavate exploratory shafts or adits. In return, the prospector promises the speculator a percentage of any profits earned. In big speculative ventures in coal, iron, or copper areas, investors might pay crews to test lands they have optioned for purchase. In placer mines, pits as well as trenches may be found across streambeds or on benches where placer miners sought gold at bedrock, often without luck.
Given this sort of activity, holes abound in mining areas. These holes are not truly mines, but prospects. Individually, these prospects may appear to lack significance. However, prospects are often associated with the phase of a region's mining history that witnessed rampant speculation or boom and bust. Entire mining camps have arisen based not on actual metal production, but on the speculative investment in prospects. Thus, isolated holes shafts or adits may qualify as separate property types. In addition, a combination of research and field work may reveal a pattern of prospect holes on the land that offers physical evidence of the speculative phase of mining development in a given region.
These prospect holes may acquire additional significance if historical archeological evidence associated with an adjacent camp or equipment is found. If the material culture possesses sufficient integrity, it will help the archeologist in reconstructing the unwritten history of the mining property. Additionally, the prospect hole may have significance if it is associated with any of the following: the first settler of an area, a prominent miner with whom no other properties are associated, or to prehistoric or aboriginal mining.
Mine Development and Exploitation Property Types
These property types are associated with the definition and extraction of an ore body. Typically found at such locations are the physical remains of hoisting works such as headframes and hoist engines; excavations such as open pits or shafts or adits; ventilation systems such as air shafts or blowers; power systems such as steam boilers or electric generator houses; drainage systems such as Cornish pumps; water delivery systems; ore bins or tipples; transportation systems such as shortline railroads or ore cart runways; and maintenance and administrative facilities such as blacksmith shops, assay laboratories, offices, and worker's housing. These structures and systems are described in the nine-volume Mining Library published by McGraw-Hill in the 1910s. Their eight-volume Library on Coal Mining series does the same for that industry.
Hard rock mines were opened with shafts or adits (tunnels). The ore was removed from large openings called stopes. Creation of these large openings required the use of new support technologies such as square-set timbering and, later, concrete supports. A hoist and head frame over a shaft used a cable and bucket or cage to hoist ore; a horizontal adit had a level or slightly inclined rail system to tap the vein. An open pit or surface pit used earth-moving machinery to remove overburden and to extract ore. At the mine surface, waste rock was dumped and ore was stored in bins to await shipment to processing plants.
Placer gold mines, abundant in the West, required a different technology than either hard rock or coal mines. For example, a placer gold mine system might include dams, penstocks, flumes, ditches and holding ponds for water; moved gravels and rock piles; sluice boxes or long toms; hydraulic nozzles; camp buildings; support structures; and, if used, dredges and their support facilities. Placer mines can extend for miles along a streambed.
Except for coal, placer gold, or the rare cases involving placer silver, platinum, or copper, most minerals are extracted from the ground in an impure and excessively bulky state and need to be upgraded before shipment to a refinery. Beneficiation the upgrading of ore to increase its value is accomplished in a processing plant. (Beneficiation, in its strictest form, includes every phase of upgrading mineral value, from the mine face to the refinery product. However, in its common use, the meaning of beneficiation is restricted to the processing of ore in a mill or concentrator, or otherwise preparing thr ore for refining. In the Iron Range of Minnesota, concentrators were called "beneficiation plants".) Beneficiation is a broad category, which includes many metallurgical processes.
The history of metallurgy is complex and rapid changes occurred during the nineteenth and twentieth centuries. Thus, one must be aware of changing processes used for metal beneficiation as well as the machinery developed to crush, concentrate, and separate metal from waste rock. Fortunately, the various processes used in connection with beneficiation property types are detailed in published textbooks. For example, Charles R. Hayward's An Outline of Metallurgical Practice (1929, revised 1940) describes over fifty different processes for extracting metals.
In general, the development of concentration mills changed through time to reduce the amount of skilled labor required for each ton of ore processed. In the book Cradle to Grave, Larry Lankton discusses the evolution of technology and its impact on Lake Superior copper mining labor and strife. It is important to link the evolution of mining technology to the impact it had on management, labor, business, politics, and communities, besides the obvious role it had in the history of science and technology.
Iron, copper, lead, zinc, and other base metal ores commonly were crushed and received initial beneficiation in concentrators that were first based upon gravity and then upon flotation processes. Understanding which process was used will help the field team determine what type of crushers and/or separation machines were used. This will also help with architectural description since mills were designed around the interior machinery metallurgy not the reverse.
Smelters represent another type of beneficiation plant. A smelter may accept high-grade ore directly from a mine or receive the concentrate from a mill for further reduction by heat. The heat and fluxes of the smelting process removed further impurities and upgraded the ore into a form known as a matte. Early smelters were small scale and operated either adjacent to, or in proximity to, the actual mines. As transportation networks evolved and fuel, space, water, labor and other factors came into play, smelters were relocated away from mines. The early plants used simple log-, charcoal-, or coal-fueled fires to melt ores into a matte that was still not pure, but rich enough in content to ship to refineries and manufacturers.
Given the evolution of the smelting process, an early nineteenth- century Pennsylvania iron "plantation," a mid-century Midwest lead smelter, and an 1860s - 1880s Colorado silver-lead smelter would all be located near the mines. By the end of the century, new economies of scale and fuel demands were removing the plants from the mines to distant locales. In the process, the industry became identified with the large conglomerates created at the turn of the century such as Anaconda in copper, the American Smelting and Refining Company (ASARCO) in silver-lead (Marcosson, 1949; Marcosson, 1957), and U.S. Steel. Smelters either operated as independent corporations that bought ores from a number of producers or as part of an integrated system linking mine, mill, and smelter. Large smelters were built at rail centers and near fuel at Pittsburgh; Pueblo, Colorado; El Paso; and the Salt Lake Valley to serve many mining districts.
Certain smelting companies, like the Cambria Iron Co. at Johnstown, Pennsylvania, and the United Verde Copper Company at Jerome, Arizona, provide examples of the evolution in the direction of high-capacity smelters. Each mining company began with small furnaces with a capacity of a few tons per day; within three decades of initial operations, the firms had mammoth plants reducing thousands of tons of iron or copper ore. Cambria included coking ovens to prepare coal, iron furnaces, roller mills that produced railroad rails and iron wire all in a one mile long complex (Brown, 1989).
Refineries convert metal into a state of purity suitable for industrial use, manufacturing, or for commercial exchange. U.S. mints and U.S. assay offices refined the gold and silver amalgamated from mills. Although private banks, express offices, and assay offices might also contain the necessary furnaces to refine the metal, after 1866 Congress required them to sell their product to the U.S. mints. (Prior to 1866, several private assay offices minted gold coins for regional use as specie.) By the turn of the century, a dozen branch mints or assay offices were operated by the Bureau of the Mint. These offices served the local mines by buying gold and helped the local economy by providing gold coins for the specie-short frontier economy, from the southern Appalachian gold fields to Alaska.
Base metals used by industry were refined at the larger smelters of the West or in Eastern refineries that offered access to international metal markets. Refineries were like smelters and operated in concert with them. The Eureka, Nevada, refinery, one of the earliest in the West, is discernable from the adjacent smelter by location and by archeological evidence. Refineries might also be associated with manufacturing works in Eastern cities, where the refinery might also be used to create blended metals called alloys. The great works of the New York City area and Chicago provided an array of metals and alloys to manufacturers. In general, field survey will be easier for refinery property types because of the amount of technical literature published about these large-scale, capital-intensive properties.
In addition to defining property types based on the three mineral processing stages, other historic mining property types exist. These property types include engineer-designed complexes, mining landscapes, and related properties.
The ideal mining situation was the bonanza mine that had its own concentration mill on site; a smelter to reduce the product into nearly pure metal; a tramway or railroad haulage system connecting the entire works; and an infrastructure of power house and lines, company housing, store, and office. This situation most often existed in iron and copper camps. For example, by the end of the 1890s the Arizona Copper Company had an integrated complex designed by mining engineers. This complex included shaft houses with hoists that lifted the ore to ore bins, narrow gauge trains that collected and hauled the ore to concentration mills, and railroads that hauled the ore from the concentration mills to the company's smelter at Clifton, Arizona.
On the other hand, smaller mine operations may have been designed by a skilled craftsman during the nineteenth century or before, or by an engineer, especially after the turn of the century. Yet, these are rarities. The lead district in the tri-state region of the upper Mississippi Valley, for example, is dotted with small mine pits where miners extracted abundant lead deposits during the antebellum period. These pits reflect a lack of system in mining as well as a lack of common knowledge about geology, ore deposits, and mining. Engineer-designed complexes reflect the development in the professional skills of mine engineering and allowed for the development of massive industrial corporations.
The National Register bulletin on Guidelines for Evaluating and Documenting Rural Historic Landscapes defines a rural historic landscape as "a geographical area that historically has been used by people, or shaped or modified by human activity, occupancy, or intervention, and that possesses a significant concentration, linkage, or continuity of areas of land use, vegetation, buildings and structures, roads and waterways, characteristic of open-pit mining landscapes found in places such as Bingham Canyon in Utah and the Mesabi Range in Minnesota, and natural features." Given the extent to which mining activity represents a human activity that modifies the natural features of the earth, many mining properties will qualify as historic landscapes.
Landscapes may represent the most dramatic visual images of mining. Mining landscapes evoke images of time, place, and historical patterns associated with past mining epochs. Mining landscapes might include ravaged landscapes denuded by nineteenth-century hydraulic mining in the Mother Lode region of California, barren strip-mining landscapes of West Virginia, gaping holes in the earth dredging landscapes in Alaska characterized by mounded tailings piles lining great stretches of creek and river beds. In addition to the visual impact of the mining landscape, the land forms created by mining provide clues to past activity. Spoil piles often indicate the location of adits and shafts, and placer tailings can help define the methods used to mine a stream even if few artifacts are present.
Mining landscapes can be characterized and distinguished by historic patterns of land use such as strip-mining, hydraulic mining, or open-pit mining; the spatial organization or layout of the landscape; characteristic natural and cultural landforms such as mine waste rock dumps, mill tailing flows, and canyons; roads and pathways; vegetation patterns related to land use such as secondary growth of plants on mine waste rock dumps; distinctive buildings and structures such as headframes or cyanide mills or coal tipples; clusters of buildings and structures such as those at mines or urban settlements; and small-scale features such as mine claim markers or fences. Landscapes can be described and evaluated by utilizing the methodology applied to rural historic landscapes. (see Guidelines for Evaluating and Documenting Rural Historic Landscapes .) In most cases, mining landscapes will be defined as historic districts for the purposes of National Register nomination.
Related Property Types
In remote placer districts, such as in parts of Alaska, isolated mining camps tent frames and small cabins that once provided shelter frequently remain as monuments to the tenacity of early prospectors and miners. Water pipelines and ditches (like the Fairhaven Ditch across Bering Land Bridge National Preserve) snake around the contours of hills for miles, often far from any other evidence of mining activity. Small mining camps may contain a limited number of buildings and structures: one or two cabins or tent frames and a few outbuildings such as a shed, several dog houses, and a cache. These small camps, while important as mining property types, are often associated with a number of other activities including hunting, trapping, and woodcutting.
Potentially significant mining-related properties can also be located in places distant from the actual mine locations. These properties include mine union halls, hydro-electric plants, school of mines laboratories, courthouses, and mine promoters' homes. Although important to the history of mining, these properties require little discussion in this bulletin. They can be evaluated and nominated according to standard practices outlined in the National Register Bulletins How to Complete the National Register Registration Form and How to Complete the National Register Multiple Property Documentation Form.
|National Register Home | Publications Home | Previous Page | Next Page|