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A review of a United States program to provide an assessment by 1974 of the impact on man, plants and animals of climatic changes due to perturbations of the upper atmosphere by the propulsion effluents of a world high-altitude aircraft fleet as projected to 1990 is presented. Some physical considerations which must be taken into account in this program are described, including representations: of the stratosphere in its unperturbed state, of the effluents of vehicles expected in 1990, of the perturbed stratosphere of 1990. of the perturbed troposphere of 1990 and 2020, of the effects of climatic changes on the biosphere and of social and economic measures of these biological effects. Author

N74-14612* Computer Software Management and Information
Center, Athens, Ga.

NASTRAN DISTRIBUTION THROUGH COSMIC
Margaret K. Park In NASA Langley Res Center NASTRAN:
Users Experiences Sep 1973 p 569-571 refs

CSCL 09B

The NASTRAN program package is one of the most important in terms of size and use in the COSMIC inventory at the University of Georgia A brief history of the COSMIC facility as it relates to the NASTRAN program package is presented, followed by a discussion of the NASTRAN disseminations. COSMIC, which is the acronym for the Computer Software Management and Information Center, is operated by the University of Georgia's Computer Center under contract to NASA. The purpose of COSMIC is to make available to the public the computer software and documentation developed as part of the NASA program. It is, perhaps, best described as a clearinghouse for the NASAsponsored computer software, although the functions specified under the contract go much further than simply duplicating the programs and documentation for distribution A sizeable portion of the workscope involves screening the programs to insure that they are free of syntax errors, that all necessary subroutines are present, and that the documentation includes sufficiently detailed instructions to allow purchasers to install and operate the program or system. Author

N74-14665 Oklahoma Univ., Norman.

MANERGY: AN ENERGY MANAGEMENT MODEL OF THE
UNITED STATES FOR THE PREDICTION OF ENERGY
DEMAND, RESOURCE CONSUMPTION, ENVIRONMENTAL
EFFECTS, THE ASSESSMENT OF NEW TECHNOLOGY, AND
ENERGY RESOURCE ALTERNATIVES Ph.D. Thesis
William Woodrow Talley, II 1973 723 p
Avail:

Univ. Microfilms Order No. 73-23921

A computerized, systems-analysis model of the United States energy system has been developed and presented in code form. The model was designed for use as a management tool for assessing the consequences of resources and fuel alternatives,

environmental controls, and technological advances. The assessment guidelines are presented as resource consumptions. environmental impacts, and balance of payment deficits to the year 2100. The model's capabilities and its inherent flexibility have been demonstrated for a baseline case and several alternatives. The base case was based on current energy use patterns, diversified resource development, projected fuel splits. population and gross national product projections, and reasonable advances in technology. The model has sufficient flexibility to include the results of the many existing and future studies on energy supply and demand. It quantifies the impacts of energy policy decisions into acceptable indices. As such, it has the capability to provide energy management guidelines necessary to make decisions on research and development priorities. legislation and regulations. Dissert. Abstr.

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N74-14678# Committee on Space Research (COSPAR), Paris (France).

COSPAR INFORAMTION BULLETIN NO. 68, DECEMBER 1973

Dec. 1973 53 p refs

Avail: NTIS HC $4.75

Past conferences are reported, and scheduled meeting are listed. The memorandum of understanding concerning EuropeanU.S. cooperation, and the data systems test are discussed along with the air mass transformation experiment. The resolution of the second assembly of the Scientific Committee on Problems of the Environment are listed. A list of satellites, and space probes from 27 June to 27 September 1973 is included. F.O.S.

N74-14680# Committee on Aeronautical and Space Sciences (U. S. Senate).

STATE OF THE AEROPSACE INDUSTRY

Washington GPO 1973 222 p Hearings before Comm. on Aeron and Space Sci., 93d Congr. 1st Sess., 26-27 Sep. 1973 Avail: Comm. on Aeron. and Space Sci.

The hearings are reported concerning the role of the aerospace industries in the aeronautics and space program. Topics discussed include: technology utilization, aviation financing. recommended investment levels for research and development, a balanced program for the future, and the national aeronautics and space objectives.

F.O.S.

N74-14684# RAND Corp., Santa Monica, Calif.
ENERGY POLICY RESEARCH AND THE STATE OF
FLORIDA

William E. Mooz Aug. 1973 17 p Sponsored by NSF and the State of Calif.

(P-5078) Avail: NTIS HC $3.00

A discussion of state energy problems and the research required to support the selection of policies designed to solve them. The example chosen is the State of Florida, in which future energy demands may be in conflict with its unique environment, and the basis for the discussion is Rand's past and present energy work for the National Science Foundation and the State of California.

Author

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On June 29. 1973. the President ordered the Federal government to achieve a 7 percent reduction in its anticipated energy consumption over the succeeding 12 months. While there are more than 80 departments and agencies within the Federal government, nearly all of the energy is consumed by the 11 cabinet departments and five large agencies. The focus of the effort has been in these 16 units. In all, a total of 20.8 percent savings in energy was made when compared to anticipated use during FY 1974. Monetary savings amounted to about $160 million. The Department of Defense is the largest user of energy in the government (86 percent), and it effected the greatest savings, mostly in its diminished use of automotive and aviation fuels. Seven other agencies met or exceeded the goal.

Author

N74-14688# National Bureau of Standards, Washington, D.C. Inst. for Applied Technology.

ENERGY CONSERVATION THROUGH EFFECTIVE UTILIZATION

Charles A. Berg Feb. 1973 55 p refs (NBSIR-73-102) Avail: NTIS HC $4.75

In two major sectors of the economy (building services and industrial processes), accounting for approximately 75 percent

of the total national energy consumption, energy utilization was found to be inefficient. It is estimated that in these two sectors, as much as 25 percent of the energy consumed annually by the nation as a whole may be lost through ineffective practices. Possible reasons for the existence of ineffective utilization are considered, and possible means of improving effectiveness of ultilization are discussed. The levels of effort to promote effective utilization of energy are identified as: (1) the effective use of present fuels in present processes. (2) utilization of presently unused energy sources, and (3) more effective investment of energy in durable and maintainable products. Author

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EPA POLLUTION REGULATIONS AND FUEL SHORTAGE: THE IMPACT ON MASS TRANSIT

Washington GPO 1973 689 p refs Hearings before Comm. on Banking and Currency. 93d Congr., 1st Sess., 26, 30. and 31 Jul. 1973

Avail: Subcomm. on Urban Mass Transportation

A hearing was held before the Subcommittee on Urban Mass Transportation of the Committee on Banking and Currency of the House of Representatives to discuss the Environmental Protection Agency pollution regulations and the fuel shortage. Specific emphasis was placed on the impact of the fuel shortage on mass transportation and recommendations for improving mass transportation as an energy saving measure. Testimony from representatives of various petroleum companies was presented to show the causes for the current fuel shortages and steps being taken to improve the situation. The effects of the proposals for reducing fuel shortages on the quality of the environment are emphasized. Author

N74-14692# Committee on Commerce (U. S. Senate).
ENERGY RESEARCH AND DEVELOPMENT, 2
Washington GPO 1973 166 p Hearing on S. 357 before
Comm. on Com., 93d Congr., 1st Sess.. 1 Mar. 1973
Avail: Comm. on Com.

A Congressional hearing was conducted to establish a Federal power research and development program to increase efficiencies of electric energy production and utilization, reduce environmental impacts, develop new sources of clean energy, and reduce the use of fossil fuels. The various features of the energy bill are: (1) establishment of a Federal Power Research and Development Board, (2) establishment of a trust fund, (3) authorization of a research program, and (4) definition of penalties for failure to comply with the provisions of the act. The report consists primarily of testimony by witnesses concerning the utilization of energy and new energy sources. Author

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The Category A computer systems at KSC (AI and A2) which perform scientific and business/administrative operations are described. This data division is responsible for scientific requirements supporting Saturn. Atlas/Centaur, Titan/Centaur, Titan III. and Delta vehicles, and includes realtime functions. Apollo-Soyuz Test Project (ASTP), and the Space Shuttle. The work is performed chiefly on the GEL-635 (Al) system located in the Central Instrumentation Facility (CIF). The Al system can perform computations and process data in three modes: (1) real-time critical mode; (2) real-time batch mode, and (3) batch mode. The Division's IBM-360/50 (A2) system, also at the CIF, performs business/administrative data processing such as personnel, procurement, reliability, financial management and payroll,

real-time inventory management, GSE accounting, preventive maintenance, and integrated launch vehicle modification status.

Author

N74-14696# Army Construction Engineering Research Lab., Champaign, III.

A DATA-BASED METHODOLOGY FOR SPECIFYING CONSTRUCTION PROJECT DURATIONS

D. W. Halpin and C. E. DeLong Aug. 1973 25 prefs (AD-767529: CERL-TR-P-14) Avail: NTIS CSCL 13/2

The report presents a method of determining the construction contract performance times for military construction projects. This method is based on information that is regularly reported as feedback during the execution of a construction contract for military construction, Army projects. By organizing the data from the manpower-utilization feedback reports, a model is formulated and mathematically derived. An example of data reduction is presented, and the results of applying the methodology to these projects are reported. A proposal of implementation of the methodology in U.S. Army Corps of Engineers, district offices is presented. Author (GRA)

N74-14850# Hughes Aircraft Co. Culver City, Calif. ECONOMICAL MULTIFACTOR DESIGNS FOR HUMAN FACTORS ENGINEERING EXPERIMENTS Charles W. Simon Jun. 1973 191 p refs (Contract F44620-72-C-0086; AF Proj. 9778) (AD-767739; HAC-P73-326; AFOSR-73-1702TR) Avail: NTIS CSCL 05/5

Experimental data collection plans are described that permit the study of from five to thirty experimental human factors. The reported plans were selected from those employed in physical science research and were suitable for human factors engineering research. The method of employing these designs is two phase. In the first phase, a large number of potentially critical factors are systematically screened in a way that identifies the more important ones In the second, functions are obtained that relate the more important quantitative factors to operate performance. Five principles that enable economical miltifactor human factors experiments to be successfully conducted are stated. (Modified author abstract)

GRA

convergence of opinion after two rounds of questioning indicates that more than one round may be unnecessary to obtain the subjective type of information discussed in the forecast. Author (GRA)

N74-15000*# Oregon State Univ., Corvallis.

THE COMPARATIVE EVALUATION OF ERTS-1 IMAGERY FOR RESOURCE INVENTORY IN LAND USE PLANNING Interim Report, Mar. - Aug. 1973

G. H. Simonson, Principal Investigator, D. P. Paine, R. D. Lawrence, W. T. Pyott, J. H. Herzog, R. J. Murray, J. A. Norgren, J. A. Cornwell, and R. A. Rogers Nov. 1973 110 p refs Original contains color imagery. Original photography may be purchased from the EROS Data Center, 10th and Dakota Ave., Sioux Falls, S. D. 57198 ERTS

(Contract NAS5-21831)

(E74-10196; NASA-CR-136369) Avail: NTIS HC $7.50 CSCL

08B

The author has identified the following significant results. Multidiscipline team interpretation and mapping of resources for Crook County is nearly complete on 1:250,000 scale enlargements of ERTS-1 imagery. Maps of geology, landforms, soils and vegetation-land use are being interpreted to show limitations, suitabilities and geologic hazards for land use planning. Mapping of lineaments and structures from ERTS-1 imagery has shown a number of features not previously mapped in Oregon. A timber inventory of Ochoco National Forest has been made. Inventory of forest clear-cutting practices has been successfully demonstrated with ERTS-1 color composites. Soil tonal differences in fallow fields shown on ERTS-1 correspond with major soil boundaries in loess-mantled terrain. A digital classification system used for discriminating natural vegetation and geologic materials classes has been successful in separation of most major classes around Newberry Cauldera, Mt. Washington and Big Summit Prairie. Computer routines are available for correction of scanner data variations, and for matching scales and coordinates between digital and photographic imagery. Methods of Diazo film color printing of computer classifications and elevation-slope perspective plots with computer are being developed.

N74-14922 RAND Corp., Santa Monica, Calif.
ENHANCING COMPUTER SYSTEM SECURITY
Dennis Hollingworth Aug. 1973 21 p refs
(P-5064) Avail: NTIS HC $3.25

One of the more significant problems in the information processing industry today is that of protecting sensitive computerized information from unauthorized access. As yet. no technique suggested or implemented appears to offer a complete solution to the problem. An attractive and cost-effective partial solution may reside in a different approach to the problemof the system/penetrator inter-action is altered via introduction of counter-penetration elements into the system hardware and software. Author

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The choice of natural atmospheres for corrosion tests is influenced by practical factors, including accessibility, security of tenure, cost, and freedom from vandalism. But these must not be allowed to outweight the technological and scientific requirements, which are discussed in detail. The variables influencing corrosion or breakdown rates under service conditions must be recognized and the one that predominates in its influence identified. Sulphur pollution, chloride from the sea, pH of rain. metal temperature, time-of-wetness, and solar radiation are discussed. A system is proposed for keeping the number of GRA

sites to a minimum.

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TECHNOLOGY FORECASTING: A CASE STUDY OF LONG-TERM REQUIREMENTS FOR RIGID AIRFIELD PAVEMENT SYSTEMS

William J. Pananos Aug. 1973 55 p refs (DA Proj. 4A0-62112-A-891)

(AD-767530; CERL-TR-A-19) Avail: NTIS CSCL 01/5

The report presents the in-action example of the Delphi method of technological forcasting, which involves polling expert opinion. Experts in the planning, design, construction, and operation of airfields were polled to develop a forecast of technical capabilities in those areas. The results demonstrate how the wide range of information obtainable from expert opinion can be conveniently presented to planners An analysis of the

N74-15214# Geological Survey, Washington, D.C.
UNITED STATES MINERAL RESOURCES

Donald A. Brobst, ed. and Walden P Pratt, ed. 1973 722 p refs

(USGS-PP-820; LC-73-600060) Avail SOD HC $9.15 Domestic Postpaid or $8.50 GPO Bookstore

Exploration and management of mineral sources are assessed for the U.S. potential in comparison with worldwide deposits.

N74-15216 Geological Survey, Washington, D.C.

MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY

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J. L. Gualtieri In its US Mineral Resources 1973 p 51-61 refs

Arsenic is produced as a byproduct and occurs in several types of deposits: enargite bearing copper-zinc-lead deposits, arsenical pyritic copper deposits, native silver and nickel-cobalt arsenide deposits, arsenical gold deposits, arsenic sulfide and arsenic sulfide gold deposits, and arsenical tin deposits. U.S. and world identified resources of arsenic are herein estimated to be 1,300,000 short tons and 17,600,000 short tons, respectively; these resources are more than sufficient to fill projected needs until the year 2000. Hypothetical resources for the United States and the world are estimated at 650,000 short tons and 14.300.000 short tons, respectively. Arsenic can be obtainable from organic shale of marine origin. Author

N74-15239 Geological Survey, Washington, D.C.
GEM STONES

Robert E. Thaden In its US Mineral Resources 1973 p 247-250 refs

Gem stones are mineral substances, other than metals, that are attractive enough for use in personal adornment or as small household objects. Diamond, sapphire, ruby, and emerald generally are considered precious stones; all other gem stones generally are considered semi-precious. Neither imitation nor synthetic gems have infringed seriously on the market for natural stones, nor are they likely to do so. Gem stones occur in most of the major geologic environments, but they do not form ore deposits in the normal sense. Since 1935, the mining of gem stones in the United States has been almost entirely a recreational activity of mineral collectors and hobbyists. The annual value of such gem production has risen from half a million dollars in 1952 to nearly $3 million in 1972 Author

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The identified, hypothetical, and speculative resources of iron are reported. The byproducts and coproducts of iron are described. The geologic environment is analyzed to show the types of iron deposits and quantities. Data are presented to show: (1) U.S. iron ore consumption, production and imports for consumption during the period 1951 to 1971, (2) sources and amounts of iron ore imported to the United States from 1961 to 1971, (3) the value of U.S. imports and exports of iron ore from 1951 to 1971, and (4) iron ore production in the U.S. from 1875 to 1971. Actions for locating additional iron deposits and methods

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Kyanite and related minerals are high-alumina silicates used mainly in the manufacture of refractory linings for metallurgical and other types of furnaces Domestic production currently exceeds consumption, and considerable tonnages are exported. Enormous resources of these minerals exist in the United States, this should permit the increase in production that will be needed to meet the demand expected during the next 25 years Production now comes largely from kyanite-quartz deposits in the Southeastern States; kyanite and sillimanite are also recovered as a byproduct from Florida ilmenite sands. Resources of deposits of these two types are very large but make up no more than 5 percent of our total resources. The remaining 95 percent or more is in deposits of micaceous schist and gneiss, mostly in the Appalachian Mountain system and in Idaho. None of these deposits is now being mined, but profitable mining of some may eventually be possible.

N74-15246 Geological Survey, Washington, DC LEAD

H. T. Morris, Allen V Heyl, and Robert B. Hall Mineral Resources 1973 p 313-332 refs

Author

In its US

The conditional, hypothetical, and speculative resources of lead are reported. The geologic environment of lead is discussed to show the geochemistry, ore mineralogy, and types of deposits. The physical, mechanical, and chemical properties of lead are described. The commerical applications of lead are shown. Data are presented for: (1) production of primary lead in the U.S. from 1830 to 1971, (2) consumption of lead in the US. from 1918 to 1971, (3) world mine production of lead in 1969 by countries, and (4) estimate of world reserves of lead by regions or countries. Author

N74-15247 Geological Survey, Washington, D.C.
LIGHTWEIGHT AGGREGATES

A. L. Bush In its US Mineral Resources 1973 p 333-355 refs

The United States is adequately supplied with both structural lightweight aggregates (scoria, volcanic cinder, pumice and pumicite, expandable clays, shales and slates, diatomite, expanded blast furnace slag. and fly and bottom ash) and ultralightweight aggregates (expanded perlite, expanded pumicite, and exfoliated vermiculite). The aggregates are low unit value. high place value materials, partly because large quantities are available and partly because normal-weight (sand and gravel) and synthetic aggregates are stiff competition. However, they have high place value, in as much as transportation costs largely determine whether they are used. Recoverable reserves of expanded clays, shales, and slates are equivalent to about half the cumulative output needed through the year 2000. Author

N74-15248 Geological Survey. Washington, DC. LIMESTONE AND DOLOMITE

Harold A. Hubbard and George E Ericksen In its US Mineral Resources 1973 p 357-364 refs

Limestone and dolomite are at or near the earth's surface over at least 10 percent of the continental areas, and the resources are extremely large. However, high-purity stone suitable for chemical and metallurgical use is restricted in extent, but its resources are large, also. For uses in which physical properties of the rock are important, as in construction, many kinds of rock can be substituted for limestone and dolomite. For uses in which the chemical properties are important, substitutes are few. generally scarce, and more costly. The largest resources of high-purity limetone and dolomite in the United States are in the central and eastern parts of the country, but details of the distribution of such stone are incompletely known. Consequently.

some potentially valuable deposits are endangered by urban spread and by zoning regulations that restrict or prevent quarrying in populous areas. Author

N74-15249 Geological Survey, Washington, D.C.
LITHIUM, CESIUM, AND RUBIDIUM: THE RARE ALKALI
METALS

James J. Norton In its US Mineral Resources 1973 p 365-378 refs

Lithium, cesium, and rubidium, though rare in comparison with sodium and potassium, are abundant relative to the apparent commercial need for them. Lithium and cesium both form independent minerals in pegmatites Lithium production from brines has increased so greatly in recent years that it has taken much of the market away from pegmatitic lithium. Rubidium forms no known independent minerals but exists chiefly as a substitute for potassium, especially in minerals formed late in the crystallization of pegmatites. Most commercial rubidium and some cesium have been obtained as byproducts of processing lepidolite. The world's proved and probable reserves of lithium, most of which are in the United States, are 1.200.000 tons, or about 400 times the 1970 consumption Additional resources in known lithium regions are about 10 million tons, and even this large figure probably could be increased many times by intensive search throughout the world. Author

N74-15250 Geological Survey, Washington, D.C.
MAGNESIAN REFRACTORIES

Alfred J. Bodenlos and T. P Thayer In its US Mineral Resources 1973 p 379-384 refs

Magnesium-bearing compounds are processed into hightemperature refractories, indispensable as linings in modern steel furnaces, chemicals; and magnesium, the lightest of structural metals. They are derived from minerals, brines, and sea water Resources from which magnesium-bearing compounds may be recovered range in size from large to practically unlimited and are globally widespread. Identified resources of magnesite throughout the world total 12 billion tons, and those of brucite several million tons. Resources of dolomite, forsterite, and the magnesium-bearing evaporite minerals are enormous, magnesiumbearing brines must constitute a resource of billions of tons; and the resource contained in sea water is practically unlimited. The bulk of magnesium-bearing compounds and the metal are recovered in the United States from sea water, brines, and dolomite, and elsewhere in the world from magnesite. Author

N74-15251 Geological Survey, Washington, DC.
MANGANESE

John Van H Dorr. II. Max D Crittenden, Jr., and Ronald G.
Worl In its US Mineral Resources 1973 p 385-399 refs

Known minable reserves and known resources of manganese are very large in relation to world consumption but are very irregularly distributed throughout the world. The United States has virtually no domestic reserves and its known resources are both very low grade and refractory to economic concentration. The principal hopes of finding domestic reserves or resources of conventional types may lie in (1) finding the source of the manganese of the Pierre Shale, conceivably buried under Pleistocene sedimentary rocks in central or western Minnesota or adjacent areas; (2) finding another Molango-type deposit by careful analysis of the distribution of manganese in certain miogeosynclinal carbonate rocks; or (3) finding the source of the high manganese concentrations in the Salton Sea brines. Much more promising modes of relieving dependence on foreign sources are by vigorously attempting to perfect techniques of effectively exploiting sea-floor nodules and by dissolving legal impediments to large-scale investment in subsea mining. Author

N74-15252 Geological Survey, Washington, DC.
MERCURY

E. H. Bailey, A. L. Clark, and R M Smith In its US Mineral
Resources 1973 p 401-414 refs

The identified and speculative resources of mercury are discussed. The commercial applications of mercury are described.

Methods for exploiting mercury production are reported Data are presented to show the following. (1) mercury production and prices from 1850 to 1971, (2) the demand and domestic supply of mercury in the US from 1850 to 1971, (3) uses and consumption of mercury in the US, and (4) mercury content of various natural substances Author

N74-15253 Geological Survey, Washington, DC.
MICA

Frank G. Lesure In its US Mineral Resources 1973 p 415-423 refs

Sheet mica has been an important strategic mineral used in electrical appliances, vacuum tubes, capacitors, and various other electrical and nonelectrical products The United States has not been self-sufficient in sheet-mica production since before the turn of the 20th century and has imported supplies to meet half to all of its needs, mostly from India, Brazil, and Malagasy Republic. Sheet mica uses are declining with advancing technology and introduction of substitutes Although the United States has undiscovered and paramarginal resources of sheet mica, the high cost of the necessary hand labor involved in mining and preparation of sheet mica deters exploration, development, or further mining Average United States scrap-mica production is increasing. but reserves and resources are adequate for foreseeable demand The United States is self sufficient in flake-mica production and is a net exporter of ground mica.

N74-15254 Geological Survey. Washington, D.C MOLYBDENUM

R. U. King, DR. Shawe, and E M MacKevett, Jr Mineral Resources 1973 p 425-435 refs

Author

In its US

The geochemistry and mineralogy of molybdenum are discussed. The types of molybdenum deposits are described Methods of prospecting for molybdenum are reported Data are presented to show the location of molybdenum deposits in the US and the estimated magnitude of world resources of molybdenum. The chemical and physical properties of molybdenum are analyzed Author

N74-15255 Geological Survey, Washington, DC
NICKEL

Henry R Cornwall In its US Mineral Resources 1973 p 437-442 refs

At the present time the free world requirement of nearly 1 billion pounds of nickel per year is supplied from deposits of nickel sulfides, mostly in Canada, and of nickel laterites. mainly in New Caledonia World resources from these types of deposits are estimated to total 70 million tons (140 billion pounds) of nickel in 7 billion tons of material averaging about 1 percent nickel. An additional 7 billion tons averaging 02 percent nickel. or 14 million tons of nickel, is estimated for sulfide deposits in the United States. The 0.2-0.4 percent of nickel universally disseminated in peridotites and serpentinites throughout the world amounts to a figure several orders of magnitude greater than 70 million tons, as does the quantity of nickel contained in deep-sea mangenese nodules: but new technological developments will be required to recover nickel successfully from these two types of occurrence Author

N74-15256 Geological Survey. Washington, DC
NIOBIUM (COLUMBIUM) AND TANTALUM
Raymond L Parker and John W Adams In its US Mineral
Resources 1973 p 443-454 refs

Niobium (columbium) and tantalum have become important metals in modern technology because of their metallurgical. electronic, chemical, and nuclear uses Both metals occur in nature almost entirely as single isotopes Nb93 and Ta181 and are present in the earth's crust in estimated abundance of 20 ppm (parts per million) and 2 ppm respectively Niobium and tantalum have strong geochemical coherence and occur together in most rocks and minerals, however, some rock types such as nepheline syenite and carbonatites contain niobium in great preponderance over tantalum. These elements occur in minerals chiefly as oxides and multiple oxides, hydroxides. a few silicates and one borate.

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