Suggestions for Prospecting

U.S. Geological Survey / Department of the Interior Suggestions for Prospecting

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For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Prospectors have contributed have been prospected although much to the development of this perhaps only at a reconnaissance Nation's mineral resources. Since scale. the time of the earliest settlement, Nearly one billion tons of surface the need for iron for tools and guns, and underground material are lead for bullets, and copper for mined annually in the United States utensils has prompted a search for to recover about one-half billion sources of these metals. The lure of tons of metallic ores, principally iron gold and silver provided the im and copper(U.S. Bureau of Mines' petus for much of the development "Minerals Yearbook, 1986," 1988, in the West between 1850 and v. 1, p. 25). Even greater amounts 1910. Later, prospectors carried out of ore must be found in the future successful ventures to fulfill the to meet the Nation's increasing country's expanding industrial needs and to replace exhausted demands for other metals such as deposits. The easily found deposits zinc, molybdenum, tungsten, have already been discovered; suc chromium, vanadium, and many cess in finding new deposits will de others. Even America's uninhabited pend more and more on modern rugged mountains or barren deserts prospecting techniques. IPir©§ij3®rock types that many kinds of geologic structures. may not be discernable by conven This knowledge is best acquired by tional ground-based prospecting academic training, but much can be methods. learned from studying reference Prospecting equipment can be books such as "Exploration and used in many ways, according to Mining Geology" (Peters, 1987), the minerals sought and the meth "Handbook for Prospectors" (Pearl, ods employed in the search. Its 1973), and others listed at the end effectiveness depends in large of this booklet. measure on the operator's aware The first technique used in a ness of its applications. For exam prospecting venture is geological in ple, radiation counters (the scin- ference. The prospector studies re tillometer, for example) not only ports, geologic maps, and cross detect radioactive minerals for the sections of a region to pinpoint uranium prospector, but can also be areas where there are structures, useful to placer prospectors. Some rocks, and minerals with which ores placer deposits contain both gold are usually associated. These areas and heavy radioactive minerals warrant further exploration. Topo such as monazite; the radiation graphic maps or aerial photographs counter points out gold concentra of these targeted areas are ob tions by detecting the associated tained and used in plotting informa monazite. A "black light" (ultraviolet tion, such as locations for sampling. lamp), commonly used in prospec This booklet briefly describes basic ting for fluorescent ore minerals prospecting techniques geochem- such as scheelite (a tungsten ore), ical, geophysical, and combination is also useful in detecting fluores methods that can help lead to the cent rock-forming minerals such as discovery of an orebody. An calcite, barite, or fluorite, which can orebody, as defined by the U.S. be indicators of associated metallic Bureau of Mines' "Dictionary of minerals. presence remains. Commonly, iron oxides and iron hydroxides form and remain as brown or yellow stains and encrustations on the sur face rocks. The solution of minerals can result in a sponge-like, iron- stained, porous rock called gossan evidence that primary minerals have been oxidized and at least partly removed. A search for these minerals at depth in such places may be fruitful. Mineral com pounds containing copper, nickel, cobalt, molybdenum, uranium, and other metals may oxidize to form brightly-colored secondary minerals on the surface rocks. These minerals are found mainly in dry regions because many of them are Scintillometer soluble in water and would be leached away in areas of heavy rainfall. The residues left in rocks after Mineral deposits have also been ore minerals have been removed by located by following float (pieces of weathering also may be clues to ore rock found on the ground surface) deposits. The rusting of iron is a uphill to its source. When rocks are familiar example of the change in being eroded, fragments are carried materials exposed to weathering. downhill by gravity and downstream Primary ore minerals (that is, by water. The source of the float minerals deposited in the rock for can be found by tracing the pieces mation by ascending ore-forming up slope. solutions) near the surface may be The systematic panning of stream oxidized and carried in solution sediment and residual soil for gold downward from their original posi or other resistant heavy minerals tion. They may be either redepos- has long been used to find bedrock ited as secondary minerals in the lodes. The gold pan, an indispen rocks below, thus enriching lower sable prospecting tool, is versatile, parts of the mineral deposit; or the efficient, inexpensive and portable. minerals may be dissolved and From a sample, an experienced completely removed, resulting in a panner can recover 80 percent of process of depletion rather than the minerals that are heavier than enrichment. quartz (specific gravity 2.65). Even Regardless of what happens to an inexperienced person can obtain the ore minerals during weathering, a concentrate of heavy minerals some evidence of their former from an ore-bearing sample that will contain virtually all of the sample's as barite, zircon, sphene, monazite, coarse gold and platinum, and a and scheelite, in addition to the high percentage of its magnetite darker minerals such as magnetite, (specific gravity 5.2) and heavier ilmenite, hematite, and sulfides. All minerals such as cassiterite, these minerals can be clues to cerussite, coulumbite-tantalite, valuable deposits in nearby or scheelite, and silver. Many minerals upstream areas. such as hornblende, biotite, mus- Other devices can be used in covite, epidote, garnet, pyrite, cin conjunction with a gold pan to test nabar, and galena are easily large samples; dozens of varieties recognized during the washing proc of sluiceboxes, rockers, suction ess, and the skillful panner can devices, and spiral concentrators recover most of these minerals are available from prospecting and present in a sample. A sample that mining equipment dealers. An inex is "panned down" to "black sands" pensive portable sluicebox for use generally also contains a number of in sampling placer deposits can be light-colored heavy minerals such made from three pieces of 1/8-inch sheet aluminum, each 3 feet long Geochemical Prospecting and about 1 1/2 feet wide. The Geochemical prospecting is based metal is shaped into flat-bottomed on systematic measurement of troughs about 1 foot wide with sides chemical properties of rock, soil, 3 inches high; the three sections glacial debris, stream sediment, are bolted end-to-end to form a water, or plants. The chemical prop 9-foot sluice. The bottom of the erty most commonly measured is sluice box is fitted with carpet, the content of a key trace element. burlap, wooden cross-slats or riffles, Zones in the soils or rocks of com or other material to trap fine heavy paratively high, or anomalous, con mineral particles. Covering the centrations of particular elements material with a coarse screen may guide the prospector to the prevents pebbles from clogging the elements in rocks or soils that con trapping material. Water is delivered stitute a geochemical anomaly (dif to the sluicebox by means of a ferent from normal). The actual pump driven by a small gasoline amount of the key element in a engine, or the sluicebox can be sample may be very small and yet placed in the stream to use the constitute an anomaly if the sam natural flow of water. The bottom ple's concentration is high relative end of the sluicebox should be part to the concentration of the surround ly closed to slow down the water ing area. For example, if most flow and to aid in trapping heavier samples of soil are found to contain particles. The carpet or burlap con about 0.00001 percent (0.1 parts taining the heavy mineral concen per million, or ppm) silver, but a few trate is removed from time to time, contain as much as 0.0001 percent placed in a tub, and thoroughly (1 ppm), the few "high" concentra washed. The washings are then fur tions are geochemical anomalies. ther concentrated by panning. Plots of analytical results on a map Working diligently, one can wash a may indicate zones to be explored ton of gravel in a day and expect to further. recover 50 percent or more of the Geochemical anomalies are black sands present. classified as primary or secondary. Many mineral deposits are not Primary anomalies result from out exposed at the Earth's surface. ward dispersion of elements by They may be concealed by thick mineral-forming solutions. High con soil cover or may lie buried beneath centrations of metals surround the layers of rock. To find them, more deposit, and the dispersion of complex techniques based on metals laterally or vertically along geochemistry, geophysics, and fractures or faults may result in a geobotany can be very helpful. "halo" surrounding the deposit. Most of these techniques require Halos are especially useful in pros specialized training, and, in some pecting because they may be hun instances, expensive equipment. dreds of times larger than the These techniques are described deposit they surround and hence below. are easy to locate. Secondary anomalies result from or both can be sampled and tested, dispersion of elements by weather and composition of the samples will ing. Some primary minerals, such reflect the chemical nature of the as gold or cassiterite, are resistant rocks in the drainage basin. The to chemical weathering and are presence of ore may be determined transported by the streams as by sampling water and sediment fragmental material. Other primary from each successive tributary and minerals may be dissolved and the by analyzing the samples for anom metals may be either redeposited alous amounts of metals. This pro locally or carried away in solution in cedure narrows the search for ore ground and surface waters. Some deposits to the most favorable metals in solution are taken up by areas. plants and trees and can be con Contamination of surficial material centrated in their tissues. Many by human activity is an ever-present studies have been made of the hazard in geochemical surveys. The metal content of residual soils over most common sources of contam sulfide deposits, and in general the ination are materials derived from distribution of anomalous amounts mine workings. Similarly, smelter of metal in the soil has been found fumes, wind-blown flue dust, and to correspond closely with the metallic objects may also con greatest concentration of metals in taminate the soils and rocks. Such the underlying rock. materials may oxidize and go into Most products of weathering in a solution, contaminating the soil, drainage basin enter the streams stream sediment, and water nearby, and rivers that flow across it. The thus masking natural anomalies. weathered products occur as chem Analytical methods used in icals in solution in the streams' geochemical prospecting must be water and in their sediments. Either sensitive enough to determine minute amounts of key elements, tellurium, thallium, tin, tungsten, accurate enough to show small dif and uranium; U.S. Geological ferences in concentration, fast Survey Bulletin 1408 (Ward, F.W., enough to permit large numbers of ed., 1975) discusses methods for samples to be analyzed in a day, testing for antimony, arsenic, and inexpensive. Wet chemical bismuth, cadmium, cobalt, copper, techniques are usually confined to fluorine, lead, mercury, molyb rapid colorimetric procedures that denum, nickel, selenium, silver, and require a minimum of equipment zinc. and materials. Instrument tech More sophisticated methods of niques, such as emission spec- analysis, particularly those employ trographic and X-ray fluorescence, ing hazardous chemical or com require expensive equipment and plicated procedures, are best done trained personnel, but usually yield in an established laboratory. Labor a lower cost per determination if atory methods usually permit about thousands of samples must be the same productivity as the camp analyzed. site methods but require a trained Wet chemical methods. chemist to perform them correctly. Analytical techniques for many Instrument techniques. The elements have been devised for use types of instruments used mostly for in geochemical prospecting. These large-scale prospecting are emis range from very simple procedures sion spectrographs, atomic absorp that can be accomplished in the tion spectrophotometers, and X-ray field, through less simple pro spectrographs because they permit cedures that can be carried out in quick identification of most an improvised laboratory at a camp elements. Instrument techniques are site, to complex procedures that re described in detail in U.S. quire a well-equipped laboratory. Geological Survey Bulletin 1770A-K Simple procedures to test for (Baedecker, 1987) and in U.S. heavy metals, as well as campsite Geological Survey Circular 948 tests mostly requiring heating and (O'Leary and Meier, 1986). leaching, are described in U.S. Emission spectrographic methods Geological Survey Bulletin 1152 have been widely used and have (Ward and others, 1963). Their the distinct advantage of giving precision is adequate for prospec results for 40 to 60 elements or ting, and the costs are not high. more in each sample. To ac Commercial kits for some of these complish the analysis, heat of an tests are available starting at electric arc or spark vaporizes a reasonable cost; they are advertised sample, which excites the atoms of in most popular mining journals. the elements in the sample so that U.S. Geological Survey Circular they emit light. A prism or diffrac 948 (O'Leary and Meier, 1986) tion grating disperses this light into describes methods for determination a spectrum containing lines of of gold, calcium, indium, lithium, definite wavelengths that are magnesium, potassium, sodium, characteristic for various elements. From the intensity of these lines, as target for the prospector than halos recorded photographically or elec produced by many other elements. tronically, the concentrations of In X-ray spectrography (some sought-after elements in the sample times called X-ray fluorescence may be determined. Many commer spectrography), bombardment with cial laboratories offering spec- X-rays excites the atoms in solid trographic analyses are advertised samples that then release their in mining journals. acquired energy in a radiation spec Atomic absorption is the opposite trum characteristic of each element. of emission spectrography, in that An X-ray spectrograph is an instru atom vapors in an unexcited state ment designed to use this property will absorb the light that they for determining the concentrations characteristically give off in an ex of elements in a sample. It requires cited state. This phenomenon is high voltages and adequate radia used in mercury detectors. The in tion shielding to protect the oper terest in mercury is twofold. Not on ator. X-ray analyses can be obtained ly a valuable metal in itself, mercury from many commercial also occurs in small quantities with laboratories. many different ores, such as those Biological prospecting. Plants, of silver, gold, lead, zinc, and cop humus, and bacteria have been per. The presence of mercury, successfully used as aids in mineral therefore, may indicate the prospecting, and under certain con presence of these other metals. ditions they may assist the prospec Further, mercury is a volatile ele tor in locating buried mineral ment and is transported as a gas deposits. So many factors are in that easily diffuses through small volved, however, that it is not possi fractures and porous rock. Thus, a ble to predict conditions under mercury halo presents a larger which biological prospecting will be helpful. However, biological pros dinavia, and the Soviet Union have pecting can be a valuable adjunct shown that chemical analysis of to conventional prospecting forest humus yields results which methods. delineate zones of gold and other Many plants, by means of their metals much more accurately than extensive root systems and the ab results from the underlying soil sorptive ability of their roots, effec (Curtin and others, 1971.) tively sample many of the elements For a review of the use of geo that are within reach and transfer botany and biogeochemistry in these elements to the branches, mineral exploration, see "Biological stems, and leaves, which can be Methods of Prospecting for chemically analyzed. Thus, under Minerals" (Brooks, 1983), "The Use ideal conditions, the plant has sam of Plants in Prospecting for pled the underlying soil or rock in Precious Metals, Principally Gold its root zone to depths of as much A Selected Reference List and as 50 feet. The advantages to the Topic Index" (Erdman and Olson, prospector of being able to sample 1985), and "Mineral Exploration- plants and thus to obtain informa Biological Systems and Organic tion about the metals that occur at Matter" (Carlisle and others, 1986). considerable depth are obvious, although problems in interpreting this information may render this Geophysical method of prospecting impractical under many field conditions. For Prospecting instance, some plants, because of Geophysical prospecting com their genetic makeup, selectively bines the sciences of physics and concentrate elements in their roots, geology to assist the prospector in stems, or leaves in higher concen exploring for both mineral and trations than are found in the energy fuel deposits. Familiar ex underlying soil and rocks. When amples include the use of scintilla ever possible, soil and rock tion counters for detecting radioac samples should also be analyzed tive uranium deposits and magnetic before concluding that a surveys for locating iron deposits. geobotanical anomaly indicates the Five major geophysical methods- presence of certain minerals in an magnetic, gravimetric, geoelectric, area. radiometric, and seismic are Forest humus also has been suc routinely used in mineral explora cessfully used to locate mineralized tion. Application of some of these rock, especially where it is hidden methods and techniques requires by soil. Elements are immobilized complex and costly instruments and and concentrated in the humus sophisticated methods of processing layer as twigs, leaves, and other and interpreting the data, but others parts of the forest vegetation fall to are relatively simple and inexpen the ground and decay. Studies in sive. Among the latter are the the United States, Canada, Scan magnetic and radiometric methods

10 and some of the geoelectric tech from a low of about 48,000 gammas niques, which are outlined here. in Texas and Florida to a high of Magnetic methods. Magnetic about 60,000 gammas in Minnesota. prospecting is based on the natural Instruments called magnetometers magnetic properties of some min are used for direct detection of erals such as magnetite. When held magnetic anomalies (that is, the near a magnetite-rich rock, the distortion of the Earth's magnetic needle in a compass behaves field by magnetic minerals in crustal erratically because the Earth's rocks). The magnetic readings over magnetic field is distorted by the weakly magnetic rocks may depart magnetic field of the rock. Rocks from local average (background) containing minerals such as mag values by 10 to 500 gammas, but netite (iron oxide), and pyrrhotite over magnetic iron formation the (iron sulfide) are usually magnetic readings may depart from back enough to be recorded by sensitive ground by 100 to 100,000 gammas. magnetic instruments. The magnetometer can be used to The common unit of measure for trace concealed rock formations the strength of a magnetic field is that have magnetic properties differ the gamma. Where not disturbed by ing from those of adjacent forma highly magnetic rocks, the strength tions. It can also be used indirectly of the Earth's magnetic field in the in the search for ore minerals. For conterminous United States ranges example, the "black sand" of

Magnetometer | placer deposits commonly contain large area. Powerlines, rails, auto grains of magnetite that affect the mobiles, and other large metallic magnetometer. Thus, it can be used objects should be avoided in any in the search for gold or other type of magnetometer survey be heavy minerals present in the black cause they create strong local sand. magnetic fields that mask the Two commonly used magnetom anomalies inherent in the rocks. eters are the fluxgate and the Today most magnetic surveys are proton. A fluxgate is an electronic airborne or marine and use total- device that measures the strength field detecting systems and vertical of the field in a particular direction. gradient systems. Instruments called The proton magnetometer's sensing vertical gradiometers measure the element is a container filled with a vertical magnetic gradient; this proton-rich liquid such as water or helps to locate the edges of mag kerosene surrounded by a coil of netic zones, rock units, and other wire; protons are subatomic par geologic features. These surveys ticles that spin about rotational provide comprehensive reliable data axes. The frequency with which the about regional magnetic trends. spin axes of the protons wobble, or Ground magnetometer surveys are "precess," after being aligned by a still used to locate anomalies from strong current passed through the small subsurface structures. coil, is directly related to the Geoelectric methods. Most elec strength of the Earth's field. This trical prospecting is based on the frequency is measured and con fact that various minerals and rocks verted into readings in units of gam offer differing degrees of resistance mas. The proton magnetometer to the flow of electric current. Elec measures the total intensity of the trical resistivity of rocks, measured Earth's field rather than the intensi in ohm-meters, can vary from sev ty in a vertical or horizontal eral thousand ohm-meters for some direction. igneous and metamorphic rocks to Magnetic surveys may be con a few ohm-meters for shales and ducted either along a series of lines clays. Some orebodies have such or in a grid pattern. The size of the low resistivity that geophysicists area being prospected and the type refer to them as conductors (con of deposit being sought determine ductivity is the inverse of resistivity). the spacing of stations. Stations For example, the resistivity of most spaced 10 to 20 feet (approximately common sulfide minerals, such as 3 to 6 meters) apart may be re chalcopyrite (copper-iron sulfide) quired to locate small magnetic and galena (lead sulfide), but not in anomalies associated with weak or cluding sphalerite (zinc sulfide), is moderately magnetic rocks, but sta very low a fraction of an ohm- tions spaced 100 feet (approximate meter. If the individual grains in a ly 30 meters) or more apart may sulfide orebody are in good elec suffice if the presence of highly trical contact with each other, the magnetic rocks is suspected in a entire orebody may offer a very low

12 resistance to the flow of electricity in the secondary fields at the sur compared to the surrounding rocks, face that can be measured and and hence be called a conductor. used to predict the presence and Other bodies, such as clay pockets, location of orebodies. graphite schists or sediments The basic measuring instruments saturated with brine can also be in the VLF method consist of one or good conductors. more induction coils, which are Many electrical techniques are used to sense the VLF magnetic used in searching for conductors field, a VLF radio receiver, and a that may be orebodies. Some re readout device. In some instruments quire very expensive and com the tilt of the VLF magnetic field plicated instruments and large field from the horizontal plane is mea crews to make the measurements, sured; in other instruments its and mathematical computations amplitiude in the horizontal direction must be applied to the data before is measured. Measurements are interpretation. Other techniques, made along lines or a grid in the however, use only moderately ex same manner that magnetic surveys pensive equipment that is easily are conducted. Ordinarily a station operated by one or two persons and spacing of 25 to 50 feet (approx require little or no use of math imately 5 to 15 meters) is adequate. ematics. For example, the VLF Powerlines, pipelines, metal fences method employs very low frequency and other large metallic objects, (VLF) radio signals, electromagnetic even if they are not steel, should be fields transmitted from a number of avoided because they act as con powerful stations around the world ductors and cause anomalous fields that continuously broadcast in the not related to orebodies. range of 15-25 kHz. The primary Another technique, the Slingram fields from these stations penetrate electromagnetic method, uses a the Earth to depths of 30-300 feet local transmitter consisting of a bat (approximately 10-100 meters) and tery powered source of alternating cause electrical currents of the current and an air- or metal-cored same frequency to flow in the induction coil that serves as the , Earth. This current creates secon antenna. The operating frequencies dary magnetic fields that can be range from about 200 Hz to 4,000 detected at the Earth's surface. In Hz. The separation between the areas where the electrical resistivity transmitter and the receiver varies of the Earth is uniform, the primary from about 100 to 800 feet (approx and secondary fields at the surface imately 30 to 240 meters). The are also uniform and are oriented in receiver for this technique mea the horizontal direction. Where the sures the in-phase and the out-of- resistivity of the Earth is not uni phase portion of the received form, however, the currents tend to signal, that is, the amount of secon concentrate along low resistance dary field that aligns with the broad paths such as may be provided by cast field and the amount that is orebodies. This causes disturbances perfectly misaligned with it. The

13 presence of a low-resistivity orebody In the self-potential method, two distorts the fields that are observed nonpolarizing electrodes placed on at the surface. In general this the surface of the Earth are con technique has a greater depth nected to a sensitive millivoltmeter, range than the VLF method and and the difference in potential is often provides data that are easier measured. Ideally, one electrode is to interpret than data from the VLF left in a fixed position, and the method. Disadvantages are that two other electrode is moved along lines persons are needed to make or a grid to measure the variations measurements and that survey lines in self potential. No calculations are must be cleared and measured in necessary unless more than one advance to work in wooded terrain. location is used for the fixed elec Another group of electromagnetic trode. Sources other than mineral devices, metal detectors, are small deposits also have variations in self portable instruments consisting of a potential. Thus, results from this wire loop suspended above the method should be correlated with ground along which an alternating other geologic evidence to indicate current flows, inducing currents the presence of an orebody. underground. The secondary mag Radiometric methods. Naturally netic fields thus created can be occurring radioactive elements such measured by audible signals. Metal as potassium, uranium, and thorium objects below the ground surface decay to other elements or isotopes (at depths of a few feet) distort by emission of subatomic particles. these fields, creating a change in Gamma rays (similar to X-rays, but the frequency of the audible signal. higher in frequency), alpha particles Electromagnetic techniques re (nuclei of helium atoms), and beta spond to the presence of rocks particles (electrons) are most com bearing significant quantities of monly emitted during this process. sulfides, graphite, or clays, to water- Radiation counters (Geiger coun filled shear zones, and to overbur ters, scintillometers, and gamma ray den, particularly when clays or spectrometers) detect differences in saline waters are present. Where intensities of radioactivity and are geologic evidence indicates the used in finding deposits of radioac possible presence of an orebody, tive minerals. The Geiger counter is magnetometer measurements may a tube filled with a gas such as help discern anomalies likely to helium, argon, or krypton. A high- represent valuable mineral deposits. voltage wire extends into the central Electrochemical methods are part of the tube. When gamma used as a follow-up to the above- radiation or beta particles pass into mentioned methods. An orebody the tube from a radioactive source, that is actively being oxidized can some of the rays collide with gas act as a natural battery, causing the molecules and produce electrically surface of the Earth above it to charged particles that are then have an electrical potential that is attracted to the central wire and different from the surrounding area. produce electrical pulses. The elec-

14 Geiger counter

trical pulses can be translated into watching the dial of the counter. dial readings of counts per minute. Radioactive deposits may produce Scintillometers use crystals of cer readings that are 10 to 100 times tain compounds, such as sodium as great as "background" readings. iodide, which emit flashes of light If the deposits are covered by even when struck by radiation. A a few tens of inches of overburden, photoelectric cell "sees" the flash however, the radiation cannot be of light or scintillation and elec detected. When a portable counter tronically counts the numbers of is used, the information should be flashes per unit of time. This can be interpreted with caution until it is transmitted to a dial reading in verified by adequate sampling and counts per minute. Scintillometers chemical analysis. are more sensitive than Geiger Exploration for uranium has counters; Geiger counters are no changed markedly over the past longer widely used, as they lack the half century. The simple ionization necessary sensitivity to find lower- chambers and Geiger counters of grade ("lean") deposits. While sen the 1940's have been superseded sitive to very small differences in by sophisticated spectrometers ot amounts of radioactive elements in great reliability and sensitivity that rocks, Geiger counters and scin- are capable of discrimination among tillometers do not show what ele uranium, thorium, and potassium. ment produces the radioactivity; Research on the movements of such distinctions are made by radon, helium, and other daughter chemical analysis of the radioactive products of uranium has produced rock. The gamma ray spectrometer new or improved tools and methods will give ppm levels of thorium, and to detect concealed uranium depos uranium,or the percent of potassium. its. Radon gas, for example, can be For ground surveys, the prospec detected in soils by use of portable tor commonly walks while listening radon counters or by radon cups to the counts on earphones or containing radiation-sensitive film.

15 All minerals on certain public lands, such as acquired lands (lands in Federal ownership ob tained by the Federal Government by purchase, condemnation, gift, or exchange) and areas offshore, are subject to special leasing laws and regulations. Further, the location of mining claims is prohibited on some public lands. Regulations governing operations on mining claims apply to most public-domain lands in the national forests and the land ad ministered by the Bureau of Land Management. The regulations ap pear in Parts 9 and 228 of Title 36, and Part 3809 of Title 43, of the Code of Federal Regulations. A mining claim can be validly located and held only after a valuable mineral deposit has been discovered. The Department has established and the courts have followed the "prudent man" test to Claim to Mineral determine what constitutes discov ery of a valuable mineral, (Chrisman Discovery and v. Miller, 197 US 313(1905).) The Secretary, in Castle v. Womble, 19 Exploration Land Decisions 455,457 (1894), Any U.S. citizen or any person defined the test as, "Where miner who has declared an intention to als have been found and the evi become a citizen may locate a min dence is of such a character that a ing claim on public lands, which are person of ordinary prudence would mainly in the Western States. Al be justified in further expenditure of though minerals are classified for his labor and means, with a reason purposes of mineral laws as locata- able prospect of success in devel ble, leasable, or salable, only oping a valuable mine then the re locatable mineral deposits can be quirements of the law have been staked and claimed under the met." Environmental factors and General Mining Law of 1872. economic costs are important con Locatable materials include metallic siderations in applying this test. In minerals (gold, silver, lead, and 1968, the U.S. Supreme Court in others) and nonmetallic minerals United Sates v. Coleman, 390 U.S. (fluorspar, asbestos, mica, and 599 (1968), approved the market others). ability test (that one must mine and

16 market a mineral at a profit). In purchase or lease. State geologists 1983, the Department of the Interior and officials at county courthouses adopted the position that only a are other sources of information reasonable prospect of success in pertaining to the acquisition of marketing, not guaranteed profit mineral rights on public or privately ability, was the proper marketability owned land. standard (Interior Regulations The prospector who succeeds in Pacific Coast Molybdenum, 90 ID making a mineral discovery must 352(1983). consider how to explore the deposit Although the number of claims in order to estimate its size and that can be held is unlimited, an ac grade. Evaluating the economic tual physical discovery on each and potential of a deposit is sometimes every mining claim on public land difficult and may require the pros must be made. Traces, minor in pector to hire an experienced min dications, geological inference, or ing engineer. Estimates of the hope of a future discovery are not length, width, and depth of a sufficient to satisfy the "prudent deposit are needed to determine man" test. Making minor im the tonnage of mineralized material provements, posting a notice, or present, and samples must be ob performing annual assessment work tained for analysis to determine the will not create or perpetuate a right grade of the deposit. Such samples or interest in the land if there are must be representative of all the no valuable minerals within the material that might be mined as claim. (See Bureau of Land ore, not just selected parts. For a Management leaflet, "Staking a review of sampling methods, see mining claim on Federal lands.") "Exploration and Mining Geology" Federal mining regulations per (second edition) by Peters (1987), taining to the acquisition of mineral chapter 16. rights on public land are adminis tered by the Bureau of Land Management. For answers to ques Services Available to tions on how and where prospecting is allowed on public lands, and to Prospectors secure copies of their publications The U.S. Geological Survey does listed in the reference section at the not identify, analyze, or assay sam end of this booklet, write to: ples of rocks, minerals, or ores at Office of Information the request of individuals or cor Bureau of Land Management (130) porations. Some State geological Washington, D.C. 20240 surveys will identify the minerals in That office can also provide ad ore samples submitted by residents dresses of their regional offices in of their State. These State agencies the Western States. can also furnish helpful information On privately owned land, the on State mining laws and the geol mineral rights must be obtained ogy of specific areas within the from the owner, generally through State.

17 The Bureau of Mines, U.S. Testing", or "Assaying"). The Department of the Interior, Bureau may limit the number of publishes the results of research on samples it will examine for an in mining, milling, and metallurgy. The dividual. Further information about Bureau occasionally makes this service may be obtained by mineralogical examinations of writing to: mineral specimens submitted by in dividuals to help determine the Assistant Director, Metallurgy mineral content, general U.S. Bureau of Mines 2401 E Street NW characteristics, and potential Washington, D.C. 20241 economic importance of a deposit of which the sample is represen Commercial laboratories or assay tative. The Bureau does not perform offices will perform chemical constit chemical constituent analyses of uent analyses of samples. A com mineral samples submitted by the prehensive list of U.S. commercial public because this service is laboratories can be found in the available from commercial assay American Society for Testing and laboratories (see the Yellow Pages Materials (ASTM) Special Technical of the Telephone Directory under Publication 333-F, "Directory of the heading "Laboratories, Testing Laboratories," (1988).

18 Maps These indexes also list special The U.S. Geological Survey maps, addresses of local map ref (USGS) publishes many maps, in erence libraries, local map dealers, addition to those contained in their and Federal map distribution cen book reports, that are useful in ters. An order blank showing prices prospecting. Among them are and giving detailed instructions for geologic maps which show rock ordering maps is included with each types, areal distribution, geologic index. structures and mineral deposits; Map indexes can also be ob and topographic maps, which show tained from Public Inquiries Offices the character and relief of land which sell USGS publications and features by means of contour lines. maps pertinent to their particular To guide users to the maps they region on an over-the-counter-only need, the USGS publishes geologic basis. The locations of these Offices map indexes and indexes to are as follows: topographic mapping for every State. USGS maps and other publica tions may be examined at many ALASKA large public and university libraries. Room 101 Descriptions of these maps and 4230 University Drive ordering instructions can be found Anchorage, AK 99508-4664 in USGS catalogs of publications. Topographic map indexes show E-146 Federal Building, Box 53 ing published maps for all areas in 701 C Street the United States are available free Anchorage, AK 99513 upon request from: Map Distribution Section CALIFORNIA U.S. Geological Survey 7638 Federal Building Box 25286, Federal Center 300 North Los Angeles Street Denver, CO 80225. Los Angeles, CA 90012 Geologic map indexes and book reports are available from: Building 3, Room 3128 Books and Open-File Reports Mail Stop 533 Section 345 Middlefield Road U.S. Geological Survey Menlo Park, CA 94025 Box 25425, Federal Center Denver, CO 80225. 504 Custom House Residents of Alaska may request 555 Battery Street Alaska indexes directly from: San Francisco, CA 94111 Alaska Distribution Section U.S. Geological Survey COLORADO New Federal Building Box 12 169 Federal Building 101 Twelfth Avenue 1961 Stout Street Fairbanks, AK 99701. Denver, CO 80294

19 DISTRICT OF COLUMBIA (or) reported but possibly not fully Department of Interior Building evaluated mineral occurrences. The 18th and C Streets, N.W. user of the MR or mineral province Room 2650 maps should have access to a large Washington, DC 20240 reference library so that pertinent references cited in each map's UTAH bibliography can be consulted. 8105 Federal Building Data compiled from aeromagnetic 125 South State Street surveys of various areas have been Salt Lake City, UT84138 published by the U.S. Geological Survey as Geophysical Investiga VIRGINIA tions (GP) maps. These have lines 503 National Center connecting points of equal value of Room 1-C-402 magnetic intensity overprinted on 12201 Sunrise Valley Drive sheets showing cultural features; Reston, VA 22092 some maps also show the geology, and thereby facilitate the correlation WASHINGTON of magnetic anomalies with geologic 678 U.S. Courthouse features. West 920 Riverside Avenue For lists of MR, mineral province, . Spokane, WA 99201 and GP maps, write to: Geologic Inquiries Group The U.S. Geological Survey has U S. Geological Survey published a series of Mineral In 907 National Center vestigations Resource (MR) maps Reston, VA 22092 which show the principal source areas of most commercial metals Results of aerial-radioactivity and minerals in the conterminous surveys conducted by the U.S. United States. These maps do not Geological Survey have been show mines and quarries but do released as published maps or as show, by symbols, major mining open-file reports. These maps are districts of specific mineral com listed in the catalogs of publications modities. A brief text accompanying of the Geological Survey. each map describes the distribution Aerial photographs for most parts and geology of the mineral com of the United States are available modity and contains a locality index from many government agencies at nominal cost. Information concern keyed to the map and a bibliog raphy. Mineral province maps (U.S. ing the availability of conventional aerial photographs for any locality Geological Survey Open-File Report 79-576 series) show, for separate can be obtained from the: commodities, areas of present min National Cartographic Information ing activity, within the 48 conter Center minous States past production, U.S. Geological Survey indication or expectation of un 507 National Center discovered minable minerals, and Reston, VA 22092

20 Information on satellite imagery implemented largely under contract and aerial and space photography with various companies, univer can be obtained from the National sities, and laboratories. NURE Cartographic Information Center, reports can be obtained from: above, or from: Books and Open-File Reports EROS Data Center Section U.S. Geological Survey U.S. Geological Survey Sioux Falls, SD 57198 Box 25425, Federal Center Radioactivity surveys of the Denver, CO 80225 United States were conducted in NURE information is also found in the 1970's by the Department of U.S. Geological Survey Circular Energy in their comprehensive Na 994, "Uranium Resource Assess tional Uranium Resources Evalua ment by the Geological Survey- tion (NURE) program. The NURE Methodology and Plan to Update program included other types of the National Resource Base" (Finch geologic and related investigations and McCammon, 1987).

References and Selected Readings Many of the following references can be consulted at large public or university libraries. Small libraries can arrange to borrow references on interlibrary loan from Federal depository libraries.

Baedecker, P.A., ed., 1987, Methods for geochemical analysis: U.S. Geological Survey Bulletin 1770A-K, variously paged. Bateman, A.M., 1981, Economic mineral deposits (3d ed.): New York, Wiley, 593 p. Boyle, R.W., 1968, The geochemistry of silver and its deposits: Geological Survey of Canada, Bulletin 160, 264 p. _ 1979, The geochemistry of gold and its deposits: Geological Survey of Canada, Bulletin 280, 584 p. Brooks, R.R., 1983, Geobotany and biogeochemistry in mineral exploration: New York, Harper and Row, 322 p. Bureau of Land Management, 1982, Patenting a mining claim on federal lands: BLM Leaflet, 12 p. _ 1971, Regulations pertaining to mining claims under the general mining laws of 1872: BLM Circular 2289, 31 p. _ 1982, Regulations for staking of mining claims: BLM Circular 2516A, 11 p. _ 1982, Surface management of public lands under the U.S. mining laws: BLM Circular 2480 A, 17 p. _ 1985, Staking a mining claim on federal lands: BLM Leaflet, 18 p. Bureau of Mines, 1986, Mineral facts and problems, 1985 edition: Bureau of Mines Bulletin 675, 956 p. _ 1988, Minerals yearbook, 1986, v. 1: Bureau of Mines, 1067 p. Carlisle, Donald, and others, eds., 1986, Mineral exploration biological, systems and organic matter: Englewood Cliffs, New Jersey, Prentice-Hall (Rubey Volume V), 456 p.

21 Chaussier, J.B., and Merer, Jean, 1987, Mineral prospecting manual: New York, Elsevier, 273 p. Compton, R.R., 1985, Geology in the field: New York, Wiley, 398 p. Cremer, M.J., and others, 1984, Chemical methods for analysis of rocks and minerals: U.S. Geological Survey Open-File Report 84-565, 153 p. Curtin, G.C., and others, 1971, Utilization of mull (forest humus layer) in geochemical exploration in the Empire District, Clear Creek County, Colorado: U.S. Geological Survey Bulletin 1278-B, 39 p. Dobrin, M.B., and Savit, C.H., 1988, Introduction to geophysical prospecting (4th ed.): New York, McGraw-Hill, 704 p. Dodd, Kurt, and others, compilers, 1986, Guide to obtaining USGS information: U.S. Geological Survey Circular 900, 34 p. Durrance, E.M., 1987, Radioactivity in geology principles and applications: New York, Wiley, 441 p. Erdman, J.A., and Olson, J.C., 1985, The use of plants in prospecting for precious metals, principally gold a selected reference list and topic index: U.S. Geological Survey Open-File Report 85-118, 19 p. Finch, W.I., and McCammon, R.B., 1987, Uranium resource assessment by the Geological Survey methodology and plan to update the national resource base: U.S. Geological Survey Circular 994, 31 p. Guilbert, J.M., and Park, C.F., Jr., 1985, The geology of ore deposits: New York, Freeman, 985 p. Haffty, Joseph, and others, 1977, A manual of fire assaying and determination of the noble metals in geologic materials: U.S. Geological Survey Bulletin 1445, 58 p. Haskins, Roger, and others, 1984, Handbook for mineral examiners: BLM Manual H-3890-1, 120 p. Heady, H.H., and Broadhead, K.G., 1976, Assaying ores, concentrates, and bullion: Bureau of Mines Information Circular 8714r, 24 p. Hood, P.J., ed., 1979, Geophysics and geochemistry in the search for metallic ores: Geological Survey of Canada, Economic Geology Report 31,811 p. Hord, R.M., 1986, Remote sensing methods and applications: New York, Wiley, 368 p. Ingamells, C.O., and Pitard, F.F., 1986, Applied geochemical analysis: New York, Wiley, 733 p. Kirschenbaum, Herbert, 1983, The classical chemical analysis of silicate rocks the old and the new: U.S. Geological Survey Bulletin 1547, 55 p. Kuzvart, Milos, and Bohmer, Miloslav, 1986, Prospecting and exploration of mineral deposits (2d ed.): New York, Elsevier, 508 p. Lacy, W.C., ed., 1983 (a), Mining geology: Stroudsburg, Pennsylvania, Hutchinson Ross (Benchmark Papers in Geology 69), 466 p. _ 1983 (b), Mineral exploration: Stroudsburg, Pennsylvania, Hutchinson Ross (Benchmark Papers in Geology 68), 433 p. Levinson, A.A., 1980, Introduction to exploration geochemistry the 1980 supple ment (2d ed.): Wilmette, Illinois, Applied Publishing, 924 p. O'Leary, R.M., and Meier, A.L., 1986, Analytical methods used in geochemical ex ploration, 1984: U.S. Geological Survey Circular 948, 48 p. Pearl, R.M., 1973, Handbook for prospectors (5th ed.): New York, McGraw-Hill, 472 p.

22 Peters, W.C., 1987, Exploration and mining geology (2d ed.): New York, Wiley, 720 p. Rose, A.W., and others, 1979, Geochemistry in mineral exploration (2d ed.): New York, Academic Press, 657 p. Stebbins, S.A., 1987, Cost estimation handbook for small placer mines: Bureau of Mines Information Circular 9170, 94 p. Stout, K.S., 1984, The profitable small mine Prospecting to operation: New York, McGraw-Hill, 174 p. Thrush, P.W., and Staff of the Bureau of Mines, 1968, A dictionary of mining, mineral, and related terms: Bureau of Mines, 1269 p. Out of print. Van Blaricom, R., ed., 1980, Practical geophysics for the exploration geologist: Spokane, Washington, Northwest Mining Association, 303 p. Ward, F.N., ed., 1975, New and refined methods of trace analysis useful in geochemical exploration: U.S. Geological Survey Bulletin 1408, 105 p. Out of print. Ward, F.N., and others, 1963, Analytical methods used in geochemical exploration by the U.S. Geological Survey: U.S. Geological Survey Bulletin 1152, 100 p. Out of print. Watterson, J.R., 1985, A procedure for estimating bacillus cereus in soil and stream-sediment samples a potential exploration technique, in Journal of Geochemical Exploration, v. 23 no. 3, p. 243-252. Wells, J.H., 1969, Placer examination principles and practice: Bureau of Land Management Technical Bulletin 4, 155 p. West, J.M., 1971, How to mine and prospect for placer gold: Bureau of Mines In formation Circular 8517, 43 p.

Additional readings Economic Geology, the Bulletin of the Society of Economic Geologists: published by Economic Geology Publishing Co., Box 74, Michigan Technological Universi ty, Houghton, Ml 49931. Semiquarterly jounal (8 issues/year). Engineering and Mining Journal: published by McGraw-Hill Publications Co., 1221 Avenue of the Americas, New York, NY 10020. Monthly. The Leading Edge: published by the Society of Exploration Geophysicists, 8801 So. Yale, Tulsa, Oklahoma 74137. Monthly. Mining Engineering: published by the Society of Mining Engineers, American In stitute of Mining Engineers, 540 Arapeen Drive, Box 8800, Salt Lake City, UT 84108. Monthly. Rocks and Minerals: published by Heldref Publications, 4000 Albemarle St., N.W., Washington, D.C. 20016. Monthly. World Mining: published by World Mining, 500 Howard Street, San Francisco, CA 94105.

23 Directories ASTM Special Technical Publication 333-F, "Directory of Testing Laboratories," (1988), includes names and addresses of commercial laboratories and describes the range of services from each. Purchase from Americal Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103. "The Leading Edge" May issue includes names and addresses of firms offering geophysical services or instruments or both. Published annually. Purchase from the Society of Exploration Geophysicists, 8801 So. Yale, Tulsa, OK 74137. "Mining Annual Review" summarizes worldwide developments in mining by com modity and by geographic area. Includes a directory to manufacturers and ser vices for the mining industry. Published annually in June. Purchase from the Mining Journal, Ltd., 15 Wilson Street, London EC2M 2TR, England. These directories may also be available in large reference libraries.

This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To ob tain a catalog of additional titles in the series "General Interest Publications of the U.S. Geological Survey," write: Book and Open-File Reports Section U.S. Geological Survey Federal Center, Box 25425 Denver, CO 80225