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By F. L. Bosqui, A. D. Wilkinson

EVEN though the world has not been crying for more copper for the last three or four years there has been some important mill and smelter construction. Discovery and development of large new high-grade copper deposits in Africa has led to the construction of extensive reduction facilities there, prominent among which is the concentrator and smelter of the Rhokana Corporation at N'Kana. Northern Rhodesia. The 3000-ton concentrator adjoins the central shaft. A little over half a mile to the southeast, at an altitude of 40,010 ft., is the smelter, designed on the site by 1. H. Wynne. It is arranged primarily to treat N'Kana copper concentrates, but can also handle concentrates and direct-smelting ore from outside sources. Excavations were started late in 1930; concrete was first poured on Jan. 6. 1931; and the first blister cop¬per was cast on March 1.9, 1932, less than fifteen months later. During this period, which included several months of heavy tropical rains, some 10,000 cu. yd. of concrete was poured and 41000 tons of structural steel erected under the supervision of construction engineer, A. Ek, with a labor force of 60 to 30 Europeans and about 300 natives. The steelwork was fabricated by Head Wrightson & Co. in England, and the boiler plant equipment furnished and erected by the International Combustion Co. Ltd.

Jan 1, 1934

By Phillip E. La Moreaux

Fluoride, generally less than 0.5 ppm, is present in ground water from rocks of Paleozoic age and older, in northern and eastern Alabama. Some of the water-bearing formations in the Coastal Plain area of the State yield water with as much as 6.8 ppm fluoride. IN June 1940, the U. S. Geological Survey, in cooperation with the Geological Survey of Alabama, began a study of the ground-water resources of the part of Alabama where water is obtained from Cretaceous rocks. The purpose of the study was to determine the quality, quantity, occurrence, and availability of ground water in that area. These studies have been expanded to include ground-water investigations in the area of Tertiary rocks, or southern quarter of the State, and certain areas in northern Alabama. The first report issued on these studies was by C. W. Carlston,1 of the Alabama Geological Survey. In the present paper all references to ground-water data for the Cretaceous area are taken from this earlier publication. In 1945, the Dentistry Division of the Alabama Department of Public Health became interested in the correlation of tooth decay and mottled enamel with the chemical quality of ground water used for public supplies in the State. Through a cooperative arrangement between the State Department of Public Health and the Ground Water Division (now Branch) of the U. S. Geological Survey, a report by the author2 was published in 1948. These two reports give accurate information on the occurrence of fluoride in the Coastal Plain of Alabama. At present, only scattered information is available on fluoride in ground water of the crystalline-rock or Piedmont area and for the Paleozoic area of Alabama, but it is hoped that in the future more complete information on the presence of fluoride in ground water in these areas can be collected. Outline of Geology and Ground Water: As described by Adams,3 the State of Alabama includes parts of two major geologic divisions, the Appalachian region and the Coastal Plain. The boundary between these divisions is irregular and is known as the Fall Line of the Atlantic and Gulf Coast States. The Fall Line enters Alabama near Phoenix City, extends westward to Wetumpka, Clanton, and Tuscaloosa, and then swings northwestward to the northwest corner of the State. The Appalachian region in Alabama includes three major provinces, the Piedmont province, the Appalachian Ridge and Valley province, and the Appalachian Plateau province (fig. 1). The rock formations in the Piedmont province in east-central Alabama are mainly of pre-Cambrian age, chiefly crystalline schists and gneisses injected by younger igneous rocks (fig. 1, I). They are faulted and folded and have a complicated structure. These rocks are the oldest and among the most complex rocks in the State. Generally, only small yields of ground water are obtained from rocks in this area. Even though ground water is of great importance for the development of domestic and farm supplies in rural areas and a few small industrial and municipal wells, yields in the area from individual wells generally range from 5 to 25 gpm and rarely exceed 50 gpm. The geologic formations of the Appalachian Ridge and Valley province and the Appalachian Plateau province (see fig. 1, II, and III) are separated on the basis of their structure. These rocks are of Paleozoic age, ranging from Cambrian to Carboniferous, and comprise a succession of formations consisting chiefly of shale, sandstone, limestone, and dolomite, aggregating many thousands of feet in

Jan 1, 1951

By Phillip E. La Moreaux

Fluoride, generally less than 0.5 ppm, is present in ground water from rocks of Paleozoic age and older, in northern and eastern Alabama. Some of the water-bearing formations in the Coastal Plain area of the State yield water with as much as 6.8 ppm fluoride. IN June 1940, the U. S. Geological Survey, in cooperation with the Geological Survey of Alabama, began a study of the ground-water resources of the part of Alabama where water is obtained from Cretaceous rocks. The purpose of the study was to determine the quality, quantity, occurrence, and availability of ground water in that area. These studies have been expanded to include ground-water investigations in the area of Tertiary rocks, or southern quarter of the State, and certain areas in northern Alabama. The first report issued on these studies was by C. W. Carlston,1 of the Alabama Geological Survey. In the present paper all references to ground-water data for the Cretaceous area are taken from this earlier publication. In 1945, the Dentistry Division of the Alabama Department of Public Health became interested in the correlation of tooth decay and mottled enamel with the chemical quality of ground water used for public supplies in the State. Through a cooperative arrangement between the State Department of Public Health and the Ground Water Division (now Branch) of the U. S. Geological Survey, a report by the author2 was published in 1948. These two reports give accurate information on the occurrence of fluoride in the Coastal Plain of Alabama. At present, only scattered information is available on fluoride in ground water of the crystalline-rock or Piedmont area and for the Paleozoic area of Alabama, but it is hoped that in the future more complete information on the presence of fluoride in ground water in these areas can be collected. Outline of Geology and Ground Water: As described by Adams,3 the State of Alabama includes parts of two major geologic divisions, the Appalachian region and the Coastal Plain. The boundary between these divisions is irregular and is known as the Fall Line of the Atlantic and Gulf Coast States. The Fall Line enters Alabama near Phoenix City, extends westward to Wetumpka, Clanton, and Tuscaloosa, and then swings northwestward to the northwest corner of the State. The Appalachian region in Alabama includes three major provinces, the Piedmont province, the Appalachian Ridge and Valley province, and the Appalachian Plateau province (fig. 1). The rock formations in the Piedmont province in east-central Alabama are mainly of pre-Cambrian age, chiefly crystalline schists and gneisses injected by younger igneous rocks (fig. 1, I). They are faulted and folded and have a complicated structure. These rocks are the oldest and among the most complex rocks in the State. Generally, only small yields of ground water are obtained from rocks in this area. Even though ground water is of great importance for the development of domestic and farm supplies in rural areas and a few small industrial and municipal wells, yields in the area from individual wells generally range from 5 to 25 gpm and rarely exceed 50 gpm. The geologic formations of the Appalachian Ridge and Valley province and the Appalachian Plateau province (see fig. 1, II, and III) are separated on the basis of their structure. These rocks are of Paleozoic age, ranging from Cambrian to Carboniferous, and comprise a succession of formations consisting chiefly of shale, sandstone, limestone, and dolomite, aggregating many thousands of feet in

Jan 1, 1951

By Ira B. Joralernon

THREATS of a coming metal famine in the United States have filled many columns in magazines and newspapers in the past three years. This asserted menace has diverted attention from the actual results of recent exploration. Because no one had bothered to look into the facts, the statistical experts assumed that little ore was being found. They often subtracted the staggering tonnage of metals produced during the war from earlier published reserves, and assumed that the difference was all we had left. Naturally, they shuddered, with all possible publicity. For their figures showed an imminent lack of nearly all the metals needed for an industrial civilization, as well as for mechanized war. They concluded that only wholesale imports and development and production of metals by Federal agencies could avert the famine.

Jan 1, 1948

By Donald F. Hammer, Donald W. Peterson

The Magma mine at Superior, Arizona, has produced over 13 million tons of ore yielding 1.5 billion pounds of copper. It is a mesathermal deposit, and, although the bulk of the ore has come from the Magma vein, most of the recent production has come from replacement deposits in limestone. The mine lies in a Precambrian and Paleozoic sequence of rocks that includes schist, diabase, quartzite, shale, and limestone; nearby, these rocks are intruded by igneous bodies of Mesozoic age that were probably the source of the ore-bearing fluids. Locally, these rocks are overlain by Cenozoic volcanic rocks and conglomerate. Layered rocks at the mine dip eastward about 30°. The area is extensively faulted, and surface faults are grouped into an earlier east-trending set and a later northtrending set. An additional set of diagonal faults that trends northwest and northeast is recognized underground. The east-trending Magma vein-fault, with its splits and branches, is the principal mineralized structure of the district. The bulk of the ore occurs in large ore shoots that plunge steeply westward and are sporadically connected by irregular ore shoots dipping gently eastward. The main ore controls apparently are selective zones of permeability related to the transverse faults. A bed of crystalline limestone near the base of the Martin Limestone (Devonian) is the host for the replacement ore bodies-discontinuous tabular pods dipping eastward parallel to the bedding. Selective permeability is again the apparent ore control, caused both by local hydrothermal solution of limestone and by deformation along faults. The principal copper minerals in the vein are chalcopyrite, bornite, enargite, tennantite, chalcocite, and digenite; these minerals vary in abundance according to a distinct zoning pattern. The upper part of the mine yielded considerable zinc as sphalerite, and the oxidized zone was rich in silver. The chief gangue minerals are pyrite, quartz, and hematite. In the limestone replacement bodies, chalcopyrite and bornite are the chief ore minerals.

Jan 1, 1968

By W. L. Saunders

(New Haven Meeting, February, 1909.) This paper deals specifically with heading-driving as distinguished from the broader term tunnel-driving. A heading is a pilot or path-finder for the main tunnel. Some headings are complete tunnels in themselves; that is, conditions at times warrant driving a heading the full diameter of the proposed tunnel. A tunnel 10 ft. in diameter might be driven to advantage through a single heading, provided the nature of the material admits, but it usually pays to drive rock tunnels of large diameter through the heading-and-bench system. Much de-pends upon the material, as in soft ground tunnels of much larger diameter are driven in a single heading. In mines, the tunnels, drifts, cross-cuts, adits, etc., are usually of small diameter, hence the driving of headings applies to completed tunnels in minim-work, except, of course, in cases like drainage-tunnels and main entries leading into coal-mines, where conditions call for tunnels of large diameter, approximating those driven for railway-service. In building aqueducts the tunnels are driven from 6 to 8 ft. in diameter up to 15 or 20 ft., while in railway-service the dimensions vary from 18 to 30 ft. in diameter. There is no department of rock-excavation so difficult as that of heading-driving. This work. also belongs to the most expensive class in rock-excavation. A heading is driven .directly in the solid. There are no lines of lesser resistance towards which to direct the energy of the blast, but. the material must be blown out by main force. The completion of the heading simplifies all the rest of the work of excavation. It is easy, for instance, to enlarge a heading either from above, below or oil the sides, by breaking towards the open face through holes approximately at right angles to the axis of the heading; or the enlargement sometimes takes place by holes driven outside

Apr 1, 1909

By V. G. Leak, R. A. Swalin

The dilhsion of silver and trace concentrations of tin in liquid silver has been rrzeasured in the temperature range from about 975° to 1350°C. The difBsion dala. fil lhe following equations: fov self-diffusion of silver The ratio of DSn to DAg is found to be about 1.34. The higher diffusivity of tin is interpreted in terms of the coullombic repulsion which results from the fact that tin dissolved in silver has a valence of +3 relative to silver. THE phenomenon of diffusion has been well-described theoretically for hard-sphere gases and solids and found to be in good agreement with experimental data for certain gases and solids. Liquid-diffusion phenomena have not been well described theoretically and there is generally a lack of good experimental data. In this investigation self-diffusion and solute diffusion in liquid silver were studied. Silver was chosen as a solvent for two main reasons. First, silver is a noble metal and the atoms are considered to have a spherically symmetric charge field; hence the liquid may be considered to be a random array of approximate hard spheres. Mercury, gallium, and other lower-melting metals were eliminated from consideration since it appears possible that in their liquid states there is some residual long-range order and directional bonding. Second, silver behaves as a monovalent solvent and, while cadmium, indium, tin, and antimony all have nearly the same atomic size, they have chemical valences relative to that of silver of +1, +2, + 3, and +4, respectively. Slifkin, Lazarus, and coworkers1-5 investigated the diffusion of these solutes in solid silver and found that their diffusion rates increased with an increase of the excess valence of the solute. In the solid state the diffusion-rate increase was calculated to be due to a change in local modulus of the solvent caused by the excess valence of the solute.1"3 For the present investigation it was planned to determine the effect of valence upon solute diffusion in liquid silver. It was deduced that a coulombic repulsion between solute and solvent might be responsible for larger volume fluctuations in the vicinity of the solute thereby enhancing the diffusion of the solute atoms. Tin was the first solute investigated and was chosen for experimental convenience. If an excess-valence diffusion effect exists in the liquid state, the solute tin with its excess valence of + 3 might show a large enough effect to distinguish it from the self-diffusion of silver in silver. The silver self-diffusion data were obviously required as a base line for comparison. In addition silver self-diffusion was investigated with a view toward examining the data in connection with the Sutherland- Einstein: Coheen-Turnbull,7 and swalin8 theories of diffusion in liquids. I) EXPERIMENTAL TECHNIQUES The diffusion coefficients for tin and silver in liquid silver were determined in separate experiments using the capillary-reservoir method of Anderson and saddingtono but following closely the experimental techniques outlined by Ma and Swa1in. The radioactive alloy bath was prepared by plating either tin-113 or silver-110 m isotope* onto 99.999 *Isotopes obtained from Oak Ridge National Laboratory. pct Ag rods.* The silver and isotope were melted *Silver obtained from Cominco Co. and mixed in a graphite crucible under a purified argon atmosphere, then outgassed for capillary filling. Some of the fused-silica capillaries were filled individually as reported by Ma and Swalin, but most were filled in a different manner. A long piece of capillary tubing was sealed off on one end and held in the system so that the open end was just above the surface of the molten alloy. The system was evacuated, the open end submerged into the alloy, and argon was admitted into the system up to atmospheric pressure. The molten alloy was forced up the capillary several inches where it solidified and was subsequently cut into segments of the proper length for diffusion annealing. The apparatus for diffusion annealing was the same as that used for capillary filling except that a Pt—Pt, 10 pct Rh therinocouple was placed in the solvent bath in order to accurately measure the temperature during the run. A diagram of the dif-

Jan 1, 1964

By E. A. Holbrook

IT may be taken for granted that a mine official knows his duties, as outlined by the bituminous mining laws of the State, he knows how coal should be mined and transported, and he has judgment on any possibly unsafe condition in his mine. Certainly, if he is weak on any of these points, there are definite ways in which he can acquire the needed knowledge. If with this knowledge the mine official has the necessary practical experience to bring self-confidence, he stands before the world as a man who knows his job. There is, however, another side to his work, one not found in hooks, a side even that may not be learned at the face even though one spends a lifetime there. The actual duties a mine official knows and performs are the tangible and definite things about his work. There are other things which may be termed intangible, because they are hard to pin down and see, and. which appear to be of equal importance in successfully handling a job and which in time determine the very success of the company itself.

Jan 1, 1930

By NEWTON B. KNOX

THE war has forced the principal industrial nations of the' world into the strait jacket of a closely controlled economy; taxes have been heaped upon all enterprises in order to maintain the armed forces and to deprive the people of the ability to bid for goods now unavailable. These restrictions, controls, and taxes are unlikely to disappear entirely after the war has been won, for debts will remain to be paid with a long period of difficult readjustment. Although the new economy will doubtless offer plentiful opportunities for the advantageous use of capital, no investor can ignore the favorable conditions offered by industry in Latin America, where taxes are relatively low and the restrictions on free enterprise comparatively mild. In mining in South America, the great international corporations have

Jan 1, 1944

By Edward Keller

(New York meeting, February, 1912.) IN a paper, entitled A Uniform Method for the Assay of Copper Material for Gold and Silver,1 A. R. Ledoux invited the assayers of this country to contribute to a symposium, in which the results of their assays of given samples of copper-matte and metallic copper would be made comparable. This symposium 2 appeared about one year thereafter; and through it and its discussion, first became generally known the fact that the ,gold-yield by the all-fire method of assaying is usually higher than by the so-called combination (wet and dry) method, in which nitric acid is employed as a solvent for the copper. In the publication alluded to, the supposed cause of gold-losses in the latter method was declared to be the solvent action of copper nitrate, or of the reduction-products of the nitric acid, upon the gold. Up to a very recent date, gold has been held to be insoluble in pure nitric acid. (The solvent action of any chlorine present in the nitric acid must here properly be disregarded as belonging in the realm of carelessness. Among later allusions to this topic, W. R. Tan Liew 3 ascribes the solution of the gold in the combination-assay entirely to the action of nitrous acid at the high reaction-temperature of copper and nitric acid ; F. B. Flinn 4 a believes the low result in gold to be due exclusively to mechanical losses-finely-divided gold penetrating through the filter-paper-but presents no experimental data confirmative of this belief; and 0. Pufahl 5 attributes the solubility of the gold in some coppers to the presence of selenium-a view which appears to be shared by many as- 1 Trans., xxiv., 575 (1894). 2 Trans., xxv., 250 (1895). 3 Engineering and Mining Journal, vol. lxix., No. 16, p. 469 (Apr. 21, 1900). 4 Engineering and Mining Journal, vol. lxxxvii., No.11, p. 569 (Mar. 13, 1909). 5 Lunge, Chemische Technische Untersuchungs Methoden, vol. ii., p. 229 (1900).

Jul 1, 1912

By John D. Sullivan

MAJOR technical advances seldom occur in a single year, and this is especially true with aluminum and magnesium where marked improvements in metallurgical processes and products took place during the war years. Nevertheless, the light metals and alloys, particularly aluminum, are advancing in commercial importance and are finding their niche in industry. New applications during the year have resulted from a better over-all knowledge of properties, handling, etc., rather than from revolutionary new developments.

Jan 1, 1948

By Eugene A. Stephenson

THE year 1935 is noteworthy for the superior legislative measures passed by several states. Sincere efforts have been made to establish equity between the various producing tracts in oil and gas fields. Outstanding legislative measures include the New Mexico law, known as Senate Bill No. 79, approved on Feb. 23; the Oklahoma law on April 22; the Texas law on April 30; and the Kansas law, which became effective July 1. Primarily designed to prevent waste, but more or less the direct out- growth of the current excess of potential oil and gas production, these statutes fall in the class of "Proration Laws."

Jan 1, 1935

By AIME AIME

MICA is perhaps our No. 1. strategic mineral problem because of its large requirements in a variety of equipment for use in the military services, and because the principal source of this material has heretofore been British India, a source now threatened partly because of distance and lack of ships. [Block mica and bauxite were added to the "most critical" list published by the W.P.B. on Nov. 6.] No satisfactory substitute has yet been found for most of the uses of mica, which largely involve electrical insulation. Brazil is now our nearest and best major source of this material. No splitting plants have yet been established there but in 1941 we imported about a million pounds of block mica from that country and in 1942 that quantity will be considerably exceeded. In Brazil, mica is found almost exclusively in the pegmatite dikes along the mountain range bordering the eastern part of Minas Gerais. A belt, roughly 180 miles long by 100 miles wide, extends from Theophilo Ottoni to Carangolo. The principal mica-mining districts in this belt are the Governador Valladares area to the north and the Espera Feliz district to the south. The dikes are usually 10 to 50 meters wide and a mile or two long and intrude the old metamorphic schist formation. They are weathered and easily mined.

Jan 1, 1942

By N. G. W., Cook

When an excavation is made underground the original rock stresses are removed from the surfaces of the excavation. These surfaces converge to partially close the excavation and the superincumbent rock mass moves down towards the excavation. If the convergence of the surfaces of the excavation were controlled, energy generated by their motion against the controlling forces could be extracted. Since the total forces in the rock mass are not significantly affected by the excavation, stress concentrations arise around the excavation, which compensate exactly for those stresses no longer transmitted through the excavation. These phenomena give rise to two general principles which provide the basis for analyzing the effects of making any underground excavation. The first of these is that the total force resulting from the stresses across any plane in the rock, including any plane through the excavation, must be the same before and after the excavation is made. The second of these is that energy must necessarily be released as a result of making an underground excavation.

Jan 1, 1969

By Francis Foley

IN examining steel under the microscope, one is constantly confronted with structures that are difficult to interpret. Recently, in a collection of samples for exhibition purposes, the writer found apiece of open-hearth runner metal, 2 in. (50 mm.) in diameter, that had been fractured for use as a sample of cast-steel structure. On polishing and etching a section for the purpose of photographing a field to typify the microstructure of steel in the "as cast" condition, a variety of structures was found (Fig. 1) so arranged as to arouse interest at once. For a distance of about 0.065 in. (1.6 mm.) from the skin of the runner, normal ingot structure was found (Fig. 2); this was followed by a zone, about 0.215 in. (5.5 mm.) wide, of considerably lower carbon content in which occurred a most pronounced Widmannstättian structure (Fig. 3); from this point on to the center of the runner, the metal was again of normal ingot structure (Fig. 4). Representative samples taken from the metal in the three zones showed the following analysis: C Ni Cr Metal from skin 0.34 1.26 0.63 Widmannstättian zone 0.21 1.18 0.63 Metal from center 0.34 1.32 0.67

Jan 7, 1919

By Frederick M. Becket

AFTER all the chronology that has been given, what is the present status of chromium steels? For the purpose of this discussion the different types of chromium steels can be divided into three classifications-those containing relatively low , percentages of chromium, say 5 per cent or less; the medium-chromium steels containing up to about 18 or 19 per cent chromium; and the steels containing still higher percentages of chromium, and some of the special alloys. Chromium has some unique effects in steel, so it is well to make a few generalizations. The affinity of chromium for carbon is great and the metal is unique in the manger in which it supplements and enhances the effects of carbon. Chromium retards -considerably the thermal transformations on cooling and exerts an opposing influence both on the absorption and precipitation of the carbides in steel. These statements make it easy to understand the fact that chromium .steels are capable of producing a hardened product at a much slower rate of cooling than is, true of plain carbon steel, and that chromium carbide or -the mixed carbides of iron and chromium do not contribute to brittleness to as great a degree as does iron carbide.

Jan 1, 1929

By SIDNEY ROLLE

ACURSORY glance through the literature on the subject reveals that the ablest minds in the land are devoting themselves to the great question of labor, of which employment is one of the fundamentals. Volumes have been written and the end is not in sight. Employment management is today about in the position that efficiency was 15 years ago. During the early days of the war, and perhaps for a year or so before, labor was plentiful. As the war progressed and Europe drew on us for munitions, employers began to compete with one another for', all, classes of labor. Labor was difficult to obtain, wages rose, the labor turnover increased, and employers began to install employment departments, welfare plans, and all sorts of schemes, but the labor efficiency dropped. As the war progressed, greater and greater production was demanded. New factors were introduced each day. The government, labor unions, industrial councils, all tended, it seemed, to make the situation almost intolerable. Wages rose to fantastic heights, the cost of living rose higher and higher, and the efficiency dropped still further.

Jan 1, 1921

By R. E. Cuthbertson

AN early appreciation by the management that Climax ore presented a challenging problem of economic concentration was responsible for the establishment, in June 1926, of an ore-testing department at the experimental plant of the Colorado School of Mines at Golden, some ninety miles from Climax. An engineering office was later organized in the same community for the design of all ore-treatment units erected at Climax during the period of rapid growth. Work of the ore-testing and design staffs was effectively co-ordinated under a common head. The primary reason for having the ore-testing and plant design departments in Golden, was to place these activities under the able supervision of A. J. Weinig, consultant for the Climax Molybdenum Co., and director of the experimental plant. A secondary consideration was the availability of excellent facilities for research in ore dressing in a highly favorable environment. Concentration of molybdenite by flotation from an ore of simple mineral composition does not appear, superficially, to present a serious problem in ore dressing but experience belies this apparent simplicity. The molybdenite content of average Climax ore is low and it is finely

Jan 1, 1946

By C. A. Stetefeldt

Jan 1, 1895

By Thomas J. Crocker, Galen G. Waddell, Eugene H. Skinner

This paper describes a method of measuring initial and long-term deformations which occur in the medium surrounding mine accessways, and discusses the importance of this type of measurement in assessing support-problem areas. Delineated are (1) description of the rock-deformation monitoring equipment, (2) results of two field tests which monitored rock deformation around 4-foot-diameter raise bores, and (3) a numerical-analysis (finite-element) technique to correlate theoretical with experimental results. Instrumentation developed provided the sensitivity and resolution needed to measure rock deformation around a full-scale raise bore during excavation. Results of the tests conducted at the Lucky Friday mine, Mullan, Idaho, show the relationships between (a) de- formation vs. time, and (b) deformation vs. bit progress. Based on theoretical evaluation of the initial deformation, the medium appeared to behave elastically. Using an estimated field stress of 5,500 psi and Poisson's ratio of 0.20, the gross modulus of elasticity of the rock was calculated to range from 3.15 to 6.0 x 106 psi (with one outlier which was determined to be >12 x l06 psi).

Jan 1, 1971