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By S. H. Lorain

This paper briefly describes the principal known commercial and near commercial deposits of gold-bearing gravel end the principal placer mining operations of Idaho County, Idaho. It is one of a series of similar papers on western mining districts. The data used in writing this paper were gathered during the summer of 1937. Information concerning gold-bearing gravels was obtained from prospectors and operators, while operators supplied most of the data on mining operations. No attempt was made actually to test the gravels. The principal object of the examination was to indicate placer areas worthy of further investigation by prospective operators.

Jan 1, 1938

By Wilson Blake

This report presents the results of a 7-year Bureau of Mines program to review, revise, and make an effective engineering tool of the microseismic method of determining the stability of rock structures. The program consisted of developing new microseismic equipment and data analysis techniques and extensive field investigations to demonstrate the effectiveness and potential of the broad-band microseismic method. The guidelines for choosing the components of a microseismic system are presented along with approximate cost figures. Different microseismic systems are discussed, including completely automated systems. Procedures for conducting microseismic investigations and analyzing microseismic data are discussed in detail. Field situations which show the full value of the microseismic technique as an engineering tool are described.

Jan 1, 1974

By Albert H. Fay, Herbert M. Wilson

The national mine-safety demonstration at Pittsburgh, Pa., was projected and undertaken in the hope that it would aid the increase of safety in the mining industry. That the national mine-safety demonstration was warranted and has served a useful purpose was evidenced by the attendance, not only at the public demonstration in Forbes Field, but also at the more special exhibit of the work of the Bureau of Mines at the arsenal grounds and at the experimsntal. mine. Nearly 2,000 persons witnessed the demonstrations and exhibits of the Bureau of Mines at the arsenal grounds on the morning of October 30, 1911. The spectators were all mine operators, miners, or persons interested in mining, and represented operations in all parts of the United States. Nearly 1,200 of these persons visited the bureau's experimental mine at Bruceton to witness ~th~explosion of coal dust. Had the weather, which was exceptionally inclement, been more favorable, there would doubtless have been a much larger attendance. At the public demonstration in Forbes Field, which· was witnessed by President Taft, from 12,000 to 15,000 persons, chiefly mining men, were present and attested their interest and enthusiasm in the minesafety exhibits by remaining throughout the proceedings, regardless of the rain which fell all the morning .. Sincethis demonstration, the organization of first-aid corps and of rescue corps has been undertaken at mines where there had previously been no such organizations. The bureau has received letters of commendation attesting the value of the demonstration in drawing· attention to the dangers and to possible means of greater safety in mining. Many of these letters have urged that the results of the demonstration be published for the guidance and instruction of those who were present. In response to these reauests the following account of the mine- BlIIeLY demonstration lias been prepared. IIi its preparation various division and section chiefs of the Bureau of Mines have cooperated. The authors acknowledge the assistance they have received from those section chiefs and other members of the bureau who contributed detailed descriptions of apparatus exhibited at the demonstration or of investigations represented.

Jan 1, 1912

By Fred W. Snow

This paper describing the mining practices at the Magma mine, Superior, Ariz., is one of a series being prepared by the Bureau of Mines on mining prac¬tices, methods, and costs in the various mining districts in the United States. At present (1929) practically all the mineral production in the Superior district is from the Magma mine of the Magma Cooper Co. The ore is mined for its copper but contains associated silver and gold. Both direct smelting ore and ore of concentrating grade are produced. The mining methods now in use at the Magma mine were adopted or developed as knowledge was gained of the physical condition of the ore bodies and the inclosing formations; the wall rock is soft and crushed and the ore is relatively hard. In general, existing methods have been adapted to fit local conditions, but some of the mining practices used were originated at this mine. Most of the ore is mined by a combination of rill stopes and pillar stopes. The pillars are extracted by underhand mining.

Jan 1, 1929

By Lorraine B. Burgin

This study by the Bureau of Mines documents the leadtime required for preliminary and detailed exploration, development of the mine, and construction of beneficiation and support facilities for selected copper deposits in Arizona. The time for major exploration ranged from 1 to 15 years, time for open pit development (or construction) was 1 to 4 years, and time for under- ground development was 4 to 8 years; one underground mine presently being developed may require 12 years to achieve production. Construction of the beneficiation plants required 8 months to just over 2 years. The data are supported by historical facts for each deposit during the leadtime stages from location of claims through exploration, construction, expansion, and leaching. The sequence of development and factors contributing to differences in the time spans are discussed. Histories are detailed for the Miami, Castle Dome, Copper Cities, San Manuel-Kalamazoo, and Twin Buttes properties; briefly summarized are the Pinto Valley, Miami East, Esperanza-Sierrita, Pima, and Mineral Park Properties. Each mining operation had its own pattern of development, and together they present a source of planning information for the development of other properties.

Jan 1, 1976

By S. H. Ash

Tunnel driving is recognized as one of the most hazardous of occupations; this is a reflection of the high accident severity rates and resultant high compensation and similar costs in this industry. Most tunnels are driven by contractors who bid for the jobs, taking into consideration the prevailing industrial insurance rates at the time the bids are placed. After the bid is secured the contractor then attempts to complete the job at the minimum cost to himself. In a sense the accident-cost item is fixed for at least one year when a policy is secured. Time is generally an important factor not only for the contractor, but also for the insurance carrier and the assured. If the assured represents a private interest, the cost burden usually is ultimately placed on the general public which avails itself of the service contemplated; if the project is a governmental enterprise the cost burden unquestionably falls upon the general public involved and on the general tax payer. For these reasons it is of vital interest to the public that accidents not only be kept at a minimum as a humanitarian objective, but also because the accident-cost burden, too frequently not even realized and considered to the degree that it should be, can assume proportions that materially affect the cost of the enterprise. The basic industrial insurance rate for tunneling in California in 1932 contemplated an earned premium of 12.12 percent of the labor pay roll. The State has been particularly engaged in large construction enterprises, some of which involve high accident cost rates, notably structural-steel bridge building, which contemplates an earned premium of 19.65 percent of the labor pay roll. When this figure is compared with the much lower rates that apply to other industries it is apparent that a heavy toll in human wreckage is taken by such engineering projects, which must be viewed as monuments to human suffering as veil as to human achievement.

Jan 1, 1933

By L. E. Cardwell

This publication contains routine analyses and related source data for 299 natural gas samples from 22 States and three foreign countries. All of the samples were collected during calendar year 1972 as part of a continuous survey of the free world for occurrences of helium in natural gas. This survey has been conducted in the United States by the Bureau of Mines since 1917. In late 1965, the survey was expanded to include foreign gasfields. The analyses published herein were made by mass spectrometer and a special helium analysis apparatus, which are described in Bureau of Mines Bulletins 4863 and 576.4 Fourteen previous publications have presented the results of 9,902 gas analyses prior to 1972. The first three, Bulletins 486,5 576,6 and 617,7 contain analyses and related source data on 5,218 gas samples collected from

Jan 1, 1973

By Stephen C. Brown

THE expansion of the world economy which has been in process since 1958 continued in 1963 and both production and consumption of minerals rose. Gross national product (GNP) rose sharply in the United Kingdom and Japan, continued to expand in the United States and Canada, and maintained a high though slightly declining rate of growth in the European Economic Community (EEC) despite the appearance of excess capacity in certain lines and inflationary pressures in Italy and France. The steel and motor vehicle industries both increased output in North America, Western Europe, and Japan. The less developed areas benefited substantially from an improvement in their terms of trade, and their export earnings increased some 8 percent in 1963; although estimates of GNP for the majority of them are 110t yet available, it is probable that this increase was partly reflected in a substantial rise of GNP.2 In the United States the expansion was steady and extended through all sectors of the economy producing no distortions likely to disturb its continuing growth; at yearend with unemployment still at about 5.5 percent of the labor force and operating rates of industry estimated at about 87 percent of capacity, there was a substantial margin for further expansion. Though the balance of payments was still in heavy deficit for the year, in the last half it was moving rapidly toward equalibrium as net exports rose and capital outflows declined; prices were relatively stable, inventories increased only slightly and the activity of mineral-consuming industries remained high, steel output rising by 11 percent to highest level since 1957 and the auto industry output equalling the 1955 record.3

Jan 1, 1964

By R. HOLROYD

The Ludwigshafen and Oppau plants are largely independent I. G. factories situated some 23 miles apart on the west bank of the Rhine facing lannheim. The former factory is a general organic chemical works specializing in dyes, dye intermediates, plastics and synthetic rubber,. while the latter is a heavy organic chemical factory producing ammonia, methanol, higher alcohols and their derivatives. Before the war much of the I. G. research and development work was carried out at Ludwigs- hafen; in particular the high pressure research section directed by Dr. Mathias Pier played a very active part in all hydrogenation developments. Apart from the possibility that a full scale hydrogenation or Fischer Tropsch plant had been erected at Ludwigshafen/Oppau during the war, the main objectives of an oil team investigation were: - (a) To obtain from Dr. Pier and his staff an advance general picture of German fuel production processes. (b) To study the fuel developments still in the research and pilot plant stage. (c) To examine any new developments in hydrogen or synthesis gas manufacture. (d) To look for new processes for production of high anti-knock fuel constituents and for new fuel additives. (e) To investigate new chemical syntheses based on raw materials obtainable from oil. The Ludwigshafen and Oppau factories were first visited by the large team listed in Appendix A during the period 25-31st March. The investigation revealed that no large plant for synthetic fuels or lubricants had been operated at this target. All the important members of the Fuel Research Section staff had been evacuated to Heidelberg and information on the work of this department was therefore limited to that contained in seized documents, the greater part of which have still to be examined in detail. Valuable information on synthesis gas production from hydrocarbon gases was obtained as well as interesting data on a num- ber of chemical syntheses. Two members of the above team Holroyd and Faragher accompan- ied by Major Tilley (interrogator) went on to Heidelberg, contacted Dr. Pier and the chief members of his staff on April 1st and obtained from them the hydrogenation information given later in the body of the report. Later, after visiting Leuna, Holroyd, Faragher and Ellis paid a second visit to Heidelberg and to Ludwigshafen/Oppau on 27th-30th May to check a number of details, particularly with respect to hydrogenation costs, and to obtain information on the pressure.conversion of water gas to hydrogen and on the manufacture of Wickel pressure vessels.

Aug 1, 1943

By Mervin D. Marshall

A quick-reaction, mine permissible rescue vehicle (MERV) was developed for use by rescue teams. The MERV is a 6-wheeled, battery-powered unit with life support equipment and instrumentation; designed for a two-man team, with provisions for handling two victims or tools in a trailer. The vehicle is 100 inches long, 56 inches wide, and maximum height of 34 inches. It can be lowered down most mine shafts and has clearance to travel mine railways. The vehicle has power to all six wheels with power transmitted separately to either or both sets of wheels. Low-pressure, high-traction tires give the vehicle the ability to handle soft, muddy mine floors, flooded areas and significant obstacles, and can negotiate a 45% grade. Power and life support are sufficient for a 4-hour mission. The life support system is a commercially-available, approved unit currently used by MESA rescue personnel. A payout wire system provides communication between the vehicle and home base over a distance of 10,000 feet. On-board monitoring of carbon monoxide, methane and oxygen is provided, with master and individual alarms to warn of gas concentrations outside pre-set limits. A lightweight, water-tight trailer was developed for carrying victims or hauling tools and equipment.

Jan 1, 1979

By Carroll W. DeKock

Thermodynamic data for selected metal sulfates were critically evaluated and compiled as part of the Bureau of Mines program to provide a scientific base for use in developing new technology and predicting the feasibility of new processes. Values for Cp°, S°, H° - H°298, - (G° - H°298)/T, ?RC, ?Gf°, and log Kf as functions of temperature are given in tabular form. Thermodynamic data were compiled for Ag2SO4, A12(504)3, A12(S04)3?6H20, BaSO4, BeSO4, BeSO4?2H2O, BeSO4?4H20, CaSO4, CaSO4?1/2H20, CaSO4?2H2O, CdSO4, CdSO4?H20, CdS04?8/3H20, 2CdO?CdSO4, Cs2SO4, In2(S04)3, K2504, KA1(S04)2, KA1(S04)2?12H20, Li2SO4, L12SO4?H20, MgSO4, MgSO4?H2O, MgSO4?2H20, MgS04?4H20, MgS04?6H2O, MgS04?7H2O, Na2SO4, Na2S04?7H20, Na2SO4?10H20, (NH4)2SO4, NH4A1(S04)2, NH4A1(S04)2?12H20, PbSO4, Rb2SO4, T12SO4, and Zr(S04)2.

Jan 1, 1986

Real economic growth for 1988 may fall short of the 3.3% projected by the Department of Commerce in August 1988 because the summer drought and intense heat in many areas curtailed output more severely than expected. The economy grew at an average annual rate of 3.0% for the first three quarters of the year, slowing in the second and third quarters. Export growth, which occurred even as the dollar edged up compared with other industrial country currencies, was an important factor in the expansion. Notable gains were posted in sales of machinery, computers, aircraft, chemicals, and telecommunications equipment. Imports increased, but not as much as exports, and the U.S. trade position was still much improved from that of 1987. Personal consumption expenditures grew slightly faster than the economy as a whole. Purchases of consumer durables showed notable strength in the first half of 1988, but slowed down in the third quarter. Despite the moderate rise in interest rates, business spending for new plant and equipment also rose and contributed to 1988 gross national product (GNP) growth. Both new business investment and export demand spurred orders for U.S.-made machine tools. Orders for machine tools for the first 8 months of 1988 were almost triple those in the corresponding period in 1987.

Jan 1, 1989

By R. C. Corey

GERMANIUM is an element that has come into widespread use in the electronics industry in recent, years. So far this increasing demand has been, met by ample supply: however, the future balance is uncertain, and the need has been recognized to discover additional domestic sources of germanium. This investigation was conducted to study the possibility of obtaining a potential supply of germanium from coal or coal ash. It has been known for some time that coal contains germanium; the discovery that By ash from coal-fired boilers often contains appreciably more germanium than the original coal suggested the possibility that coal ash might be an abundant and economical source of this element. In this study the concentration of germanium was determined in numerous samples of coal and ash. A number of miscellaneous waste materials also were examined in the course of the investigation; the results are reported as a matter of general interest. The methods and equipment employed are discussed in detail. Sample-preparation and analytical techniques are described in the appendix. Spectrographic analyses were made on a total of 639 samples, including coal, coal ash, slap ash from lignite and peat, wood ash, and various inorganic materials. Qualitative analyses were run on all samples, and quantitative determinations were made on those samples that contained enough germanium to be measured by this method The lower limit at which germanium can be determined quantitatively by spectrographic analysis is 50 parts per million (p. p. m.), but concentrations of less than 20 p. p. m. can be detected qualitatively.

Jan 1, 1959

By Earl L. Fosse

"Preliminary examination of the Khayyam mine indicated that greater reserves of copper might be found by trenching, sampling, detailed geological and topographical mapping, and diamond drilling. The deposit seemed to be a potential source of sulfur, also, for use in the manufacture of paper pulp.Formal examination of the Khayyam mine by the Bureau of Mines was a follow-up of a preliminary examination made by W.S. Wright and the author on October 19-21, 1944. John Reed and W. S. Twanhofel, of the Geological Survey, visited the property during the summer of 1943 and suggested that the prospect be examined further.Preliminary examination of the Stumble-On claim was made July 1-3, 1945, concomitant with the formal examination of the Khayyam mine 11/2 miles to the west.In its program of exploration of mineral deposits, the Bureau of lanes has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy, It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts pre¬liminary examinations, performs the actual exploratory work, and prepares the final report, The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests. Both these branches arc under the supervision of Dr. R, S. Dean, assistant director.Special acknowledgment is due Robert S. Sanford, acting chief, Alaska Division, Mining Branch, for his help in the preparation of this report and during the project work.The Khayyam property is situated at 550 18’ north latitude and 1320 24’ west longitude on Prince of Wales Island in Southeastern Alaska. (see fig. 1.) The mine adit is 2,350 feet above sea level, near the summit of a mountain ridge, and 2.8 miles in an airline southwest of the head of McKenzie Inlet, a southern branch of Skown Arm. Skowl arm is navigable by ocean-going vessels .to the mouth of McKenzie Inlet, where reefs and rocky islands limit the channel width to 50 yards. Beyond this point the inlet widens to nearly half a mile. Coast and Geodetic Survey chart 8142 indicates from 12 fathoms of water at this narrow neck to more than 30 fathoms throughout the remainder of McKenzie Inlet, The old ore bunker and dock at the head. of the inlet are beyond repair. A new ore bunker and dock would have to be built if a large-scale mining operation were established.The mine can be reached by trail along the western ridge that lies on the west bank of Omar Creek. The trail is approximately 4 miles in length. The grade is rather steep to an elevation of 1,500 feet, but the last 21 miles can be traveled over gentle slopes along the crest of the ridge.Ketchikan is 30 miles by air and 42 miles by water from the head of McKenzie Inlet. Feed, hardware, fuel oil, lumber, and explosives can be purchased at Ketchikan and delivered by boat to McKenzie Inlet. By using an airplane, all small equipment and camp supplies could be using an airplane, all small equipment and camp supplies could be dropped with cargo parachutes near the mine."

Sep 1, 1946

By D. J. Dollhopf

A week-long selective overburden handling dragline op ration was conducted at a strip mine near Colstrip, Montana. The objective of the demonstration was to hvdrologically isolate a saline overburden zone during placement in the spoil piles. The saline zone had concentrations considered inimical to successful reclamation and was potentially dangerous to future water quality in the spoils aquifer. The zone was identified after review of chemical data for overburden samples collected from the intense 60 m grid drilling pattern. The saline zone in the overburden was: 1) handled in a normal manner; 2) segregated and buried; and 3) segregated, buried, and covered with a relatively impermeable 1.0 m thick clay cap. The method used to formulate this demonstration, the demonstration itself, and the monitoring and evaluation techniques are described in this report. Observation wells were installed to monitor ground water in the overburden, Rosebud coal, and McKay coal. Data from these wells were, used to estimate post reclamation water levels and to evaluate recharge and water movement characteristics in the vicinity of the demonstrations. The inimical zone was successfully handled in a selective manner with a minimum of delays. Economic analysis indicated cost of these selective burial operations to be about 1.1 to 1.5 times the cost of the normal operation at this particular mine site. Long term monitoring will be required to evaluate the effectiveness of these handling techniques in hydrologically isolating undesirable overburden materials.

Jan 1, 1977

By D. Harrington

"FOREWORDVirtually all government agencies undertook many additional responsibilities during the period immediately preceding World War II; these responsibilities increased vastly in importance and scope after the actual declaration of war following the attack on Pearl Harbor. The Bureau of Mines was one of the agencies thus affected, and it was called upon to perform many duties foreign to its normal peacetime activities.The Health and Safety Division of the Bureau of Mines, at that time designated the Health and Safety Branch, was given several important and difficult duties and responsibilities of an unusual nature because of the war while of necessity-continuing its normal functions of assisting the mineral industries in the preservation of life and health and the protection of property, this being of especial importance in wartime because of the pre-eminent importance of having maximum output of essentially all types of mineral products. Some of these additional functions were given to the Health and Safety Division because the organization of the Division, with its field set-up dividing the Nation into districts with competent, experienced personnel in charge of its work, provided the nucleus of personnel and procedure through which rapid and smooth expanded functioning was feasible.In addition to the responsibilities directly attributable to definite war activities, such as the administration of the wartime Federal. Explosives Act and the Mineral Production Security Branch a new branch (then designated division) was formed to investigate coal-mine health and safety problems after the enactment of the Federal Coal-Mine Inspections and Investigations Act, which became a law on May 7, 1941, but which actually began to function actively after the declaration of war in December 1941.The purpose of this publication is to provide a brief historical record of the activities of the Health and Safety Division as a whole and of its individual branches during the war. The detailed record has been filed in the Archives Building, Washington, D. C."

Jan 1, 1949

By A. D. McMahon

This survey is one of a series of Bureau of Mines publications designed to serve the needs of Government and industry for comprehensive information on mineral commodities and activities. Copper, a versatile metal, has been vital to all civilizations from prehistoric times to the present. Its essential value in antiquity and until the nineteenth century arose from its malleability and ease of working, its corrosion resistance and durability', its attractive colors in alloyed and unalloyed forms, and, of course, its availability. The principal uses were for tools, utensils, vessels, weapons, pipe, statuary and other objects of art, and for building and architectural pur£~ses where formability, permanence, and beaut)" were necessary qualities. Utilization of copper based on these physical and mechanical properties has grown tremendously for commercial, structural, mechanical, architectural, and art items; and its capacity for forming numerous alloys has led to a myriad of applications from miniature copper and brass eyelets to huge bronze battleship propellers. The early nineteenth century marks the epoch of the greatest use of copper, transmitting electrical energy. This particular property of copper is fundamental to the spectacular growth of the electrical industry and all associated industries relying on electricity for power, light, and heat. More than half of all copper produced is used for transmission of electricity. The copper industry has been able to expand along with the mounting demand because of the ever increasing discovery of resources in the world and advances in mining, metallurgical, and fabricating technologies. World production and consumption rose progressively from about 18,000 tons in 1800 to more than 4.5 million tons in 1960. The estimated world reserve of primary- copper has more than doubled since 1935, being 212 million tons in 1960. Ninety percent of this reserve is credited to eight countries-the United States, Canada, Chile, Peru, the Soviet Union, Poland, Northern Rhodesia, and the Republic of the Congo. The United States share is 32.5 million tons of copper in ore, averaging approximately 0.9 percent. Another reserve being accumulated in the industrial countries of the world is copper products now in use that will eventually be discarded as scrap and become available for recovering secondary copper. In the United States this resource of more than 30 million tons, provides about one-fourth of the annual supply.

Jan 1, 1965

By Sean Gallagher, William S. Marras, Alan S. Litsky, Velimir Matkovic, Deborah Burr, John Landoll

Study Design. Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample. Objectives. To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure. Summary of Background Data. A previous investiga¬tion evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 ± 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0°, 22.5°, and 45°). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens. Methods. Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0°, 22.5°, or 45°). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Results. Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean ± SD, 30.7 11.1 g per motion segment vs. 27.8 ± 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%. Conclusion. Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5° flexion were similar to that of older specimens at 0° flexion, and survivorship of young specimens at 45° flexion was similar to the older cohort at 22.5°. Key words: biomechanics, low back disorders, fatigue failure, age, motion segments, vertebral endplate fractures, torso flexion, lifting, bone mass. Low back disorders (LBDs) are a major cause of both short- and long-term occupational disability in the United States, and it is clear that workers in certain occupations are more susceptible to LBD.2-5 Specifically, epidemiologic studies have shown that jobs involving heavy physical demands such as construction,2,3 mining,2,4 and farming,5 engender increased risk of back pain. These occupations are thought to experience high LBD rates as a result of their extreme postural and manual lifting demands. Studies have shown that jobs involving significant lifting 6-9 and jobs that involve frequent bending10-12 are associated with increased LBD risk. Workers in the mining industry, in particular, often have to lift heavy materials in restricted workspaces that compel torso flexion. An understanding of the impact of repeated loading of the spine in flexion on fatigue failure of spinal tissues is thus a critical issue for our research agency, which is concerned with reducing the pain and disability associated with LBD in the mining industry. It is well accepted that loads experienced by the spine during manual lifting tasks are sufficient to cause fractures in the endplates of lumbar vertebrae, particularly on repeated loading. 13-15 Endplate fractures may not be painful in and of themselves 16; however, evidence suggests that the process of internal disc disruption and disc degeneration may be initiated via endplate fractures. 16,17 It has been shown that endplate damage will alter the distribution of stress in the disc, resulting in buckling of the lamellas of the internal anulus.17 Once this process has been initiated, repeated spine loading will cause additional disruption of the anular fibers, resulting in formation of significant fissures or tears. 11-21 If these tears occur near or extend close to the outer portions of the anulus, a wound healing process is initiated, which involves infiltration of mast cells, macrophages, and re¬lease of cytokines and growth factors. 21 The presence of these infiltrates has been strongly linked to discogenic low back pain. 21,22 Indeed, for patients experiencing chronic low back pain, the prevalence of internal disc disruption is at least 39%,19 which represents the most

By Oliver Bowles

The term" sandstone" is applied to a rock composed of mineral grains smaller than pebbles, cemented together more or less firmly. "Conglomerate" is the name given to a rock composed of pebbles, or pebbles and bowlders, of various sizes cemented together. If the pebbles are large and well rounded the rock is sometimes called " pudding stone." Although the term "sandstone" includes all varieties, certain specific terms are applied to types characterized by particular compositions, colors, or uses. "Quartzite" is a variety in which the individual grains are so firmly cemented together with quartz that the rock will fracture as easily through the grains as through the cement; "ferruginous sandstone" is one rich in iron as cementing material, or as grains, or both; "micaceous sandstone" is one in which mica is prominent; " arkose" is a feldspathic or granitic sandstone composed of angular grains; "calcareous sandstone" is one containing considerable calcium carbonate; and" argillaceous sandstone" is one containing considerable clay. The term "flagstone" is used for a rock that splits readily into sheets suitable for flagging; "freestone" for rock than can be cut or carved readily, and with equal ease in all directions; and" ganistel'," in the United States, for sandstone suitable for the manufacture of refractories. Others are named from their characteristic colors such as " bluestone," " redstone," or " brownstone."

Jan 1, 1917

By Wallace W. Key

This report concerns types, quantities, specifications, and uses of non-metallic minerals as a basis for improving their supply, conservation, and utilization. Supply-demand details concerning mineral fillers, rooting granules, and roofing rock used in asphalt are incorporated in this report, along with highlights on production and sales of rooting, floor tile, and other related asphalt products of California. Comparable data for the United States are included. Although large quantities of commercially prepared mineral fillers are used in asphalt for paving and related applications in other States, addition of commercial fillers for these uses rarely is required in California because of the natural tines available. On the other hand, California manufacturers of asphalt products other than having utilize about 300,000 tons of asbestos, diatomite, limestone, mica, soapstone, and other nonmetallic minerals as filler, mainly for reeling and flooring. Also about 500,000 tons of roofing, granules is produced in California, most of which goes into roofing manufacture in California. In addition. A significantly large and growing tonnage of relatively coarse mineral aggregates Ire used on low-angle, built-up, asphalt roofs to produce in attractive surface and offer protection against the clements. Clearly ill minerals used in asphalt products manufactured in California come from local sources, except asbestos and mica--and there are indications that local deposits of those commodities could be utilized in some use categories.

Jan 1, 1966