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By A. A. Gustafson

In diamond or churn drilling for the prospecting of ore bodies, two products can be used for quantitative analyses; i.e., the core and the cuttings, or sludge. Some operators prefer an assay of core; others insist that the sludge be sent for analysis. Both must recover the sludge for check samples or for assays if there is no core recovery for any particular section of the diamond-drill hole. The Freeport Sulphur Co. found that numerous cumbersome sludge boxes or barrels were inconvenient and delayed drilling. The sludge settled slowly in the ordinary shallow, rectangular diamond-drill boxes and its total removal from the container was difficult, time-consuming and unsatisfactory; and sampling of deposits of which the metal contents are easily concentrated, as in ores containing cinnabar, gold and silver, is subject to error if the boxes are not thoroughly cleaned. Mr. Charles Ballard, dredge superintendent at Freeport's operation at Grande Ecaille, Louisiana, developed a portable cone while he was in charge of prospecting a mercury property near Tonopah, Nevada, in 1940. Ballard later improved the design while the settler was being used at a manganese property in New Mexico. The operation is based on the "free settling" of comminuted particles in a quiescent liquid. The ordinary sludge box discharges over a lip 8 to 12 in. wide and consequently the water has sufficient velocity so that the discharge water is never clear. The cone settler used by Free-port Sulphur Co. discharges over the entire circumference, which gives a discharge ltp of 9 ft. in the size of cone used at the cinnabar and manganese prospects. Consequently, the velocity of the discharge water is slow enough so that all fine material settles and the discharge water is clear. When the drilling of a sample interval is complete, the sludge can be drawn off by the time the driller is ready to cut another sample. Thus, only one cone is needed per drill. The cone has been used by Freeport successfully in churn-drilling a manganese deposit, in diamond-drilling a mercury deposit, and in diamond-drilling a deposit of ore containing tin, copper, gold and silver. The cone is greatly superior to the old methods of collecting sludge and is now used on all Freeport drilling campaigns in the western states, both for surface and underground drilling. Fig. I shows the important details of a cone designed for average operating conditions, 30 in. in diameter and 36 in. high. Abnormal conditions may require some revisions in design. Fig. 2 shows a working drawing. A hose or pipe larger than the one used to convey water from the pump to the swivel head of the string of rods is connected to the stuffing box at the collar of a diamond-drill hole, The usual T-connection is used. It is not necessary to use a stuffing box if the top of the cone can be placed lower than the collar of the hole. Then the return water and cuttings can be made to flow by gravity. This hose or pipe discharges the cuttings of the drill bit and the return

Jan 1, 1943

By A. A. Gustafson

IN diamond or churn drilling for the prospecting of ore bodies, two products can be used for quantitative analyses; i.e., the core and the cuttings, or sludge. Some operators prefer an assay of core; others insist that the sludge be sent for analysis. Both must recover the sludge for check samples or for assays if there is no core recovery for any particular section of the diamond-drill hole. The Freeport Sulphur Co. found that numerous cumbersome sludge boxes or barrels were inconvenient and delayed drilling. The sludge settled slowly in the ordinary shallow, rectangular diamond-drill boxes and its total removal from the container was difficult, time-consuming and unsatisfactory; and sampling of deposits of which the metal contents are easily concentrated, as in ores containing cinnabar, gold and silver, is subject to error if the boxes are not thoroughly cleaned. Mr. Charles Ballard, dredge superintendent at Freeport's operation at Grande Ecaille, Louisiana, developed a portable cone while he was in charge of prospecting a mercury property near Tonopah, Nevada, in 1040. Ballard later improved the design while the settler was being used at a manganese property in New Mexico. The operation is based on the "free settling" of comminuted particles in a quiescent liquid. The ordinary sludge box discharges over a lip 8 to 12 in. wide and consequently the water has sufficient velocity so that the discharge water is never clear. The cone settler used by Freeport Sulphur Co. discharges over the entire circumference, which gives a discharge lip of 9 ft. in the size of cone used at the cinnabar and manganese prospects. Consequently, the velocity of the discharge water is slow enough so that all fine material settles and the discharge water is clear. When the drilling of a sample interval is complete, the sludge can be drawn off by the time the driller is ready to cut another sample. Thus, only one cone is needed per drill. The cone has been used by Freeport successfully in churn-drilling a manganese deposit, in diamond-drilling a mercury deposit, and in diamond-drilling a deposit of ore containing tin, copper, gold and silver. The cone is greatly superior to the old methods of collecting sludge and is now used on all Freeport drilling campaigns in the western states, both for surface and underground drilling. Fig. I shows the important details of a cone designed for average operating conditions, 30 in. in diameter and 36 in. high. Abnormal conditions may require some revisions in design. Fig. 2 shows a working drawing. A hose or pipe larger than the one used to convey water from the pump to the swivel head of the string of rods is connected to the stuffing box at the collar of a diamond-drill hole. The usual T-connection is used. It is not necessary to use a stuffing box if the top of the cone can be placed lower than the collar of the hole. Then the return water and cuttings can be made to flow by gravity. This hose or pipe discharges the cuttings of the drill bit and the return

Jan 1, 1943

By Walter Weeks

THERE is very little useful material in the litera-ture on the construction of manometers, so each experimenter must devise his own instrument. I have experimented for a number of years and have finally built one that is satisfactory. If we are to obtain accurate friction factors in mine-ventilation problems we must use accurate instruments. The most simple and convenient instrument for the mea-surement of small pressures is the inclined manometer or U-tube. By changing the angle at which the tube is set, any desired magnification of the pressure reading may be obtained. The first question in regard to the manometer is: What liquid shall be used? Alcohol, in my opinion, is the best. It does not cling to the glass and it does not attack the rubber tubes. The next problem is the setting of the instrument at the proper angle. One method is illustrated in Fig. 1. The base plate AC is made horizontal by a level bubble. The plate AB, which carries the U-tube, is hinged at A. The angle z which AB makes with the horizontal may be made any value by pinning the end B at the calculated position on the arm CD. Such an instrument may be designed to read directly in inches of water if a liquid of constant specific gravity is used. If the specific gravity varies, a calculation is necessary to convert the reading into inches of water.

Jan 1, 1923

NATURE produces iron ore abundantly in many regions of the world, especially in Italy where not only is there a great abundance of it but also there are various kinds. In these our Tuscan parts it is a very familiar thing, since we are situated close to the island of Elba which is so overflowing and rich in this ore that it surpasses every other place where it is found. Thus not only do the regions of Tuscany share its great quantity because of their proximity, but more than two-thirds of Italy as well as Sicily and Corsica are supplied, and perhaps some more distant place. In addition, this ore is of such perfection that it

Jan 1, 1942

By R. D. Springer, R. L. Wilcox, P. A. PALMARTAN, R. K. Waring, E. A. Anderson

A knowledge of the mutual liquid solubility of zinc and lead is of importance in various phases of zinc metallurgy. The determination of this solubility has been the subject of numerous investigations, but unfortunately the results vary widely, particularly at higher temperatures, and it has been impossible to decide what data are most reliable. It was decided to investigate the matter and in view of the disagreement in the published results, it was felt necessary to take rather unusual precautions to insure the reliability of the data. For this reason determinations were made by four different methods, and the procedures of several of the previous investigators were duplicated. The previously used methods can be divided into two classes: methods involving freezing the entire melt and taking samples of the lead-rich and zine-rich phases in the solid state,l,2 and methods in which the samples are taken while the bath is liquid and at the desired temperature.3,4 Data obtained by methods involving freezing the entire melt show much lower solubility of lead in zinc than methods in which the liquid is sampled at temperature. The latter method was used by Spring and Romanoff5 and by Hass and Jellinek.6 The results of these two investigations are in agreement at temperatures near the melting point but at higher temperatures Hass and Jellinek find a higher mutual solubility. The low-temperature section of the zinc-lead equilibrium diagram is given by Peirce and Anderson.7 The diagram is based on the data of Hodge and Heyer,8 Arnemann,9 and Peirce.10

Jan 1, 1934

By William Waters Van Ness

The Pierrefitte mines, situated in the South of France, in the district of the Hautes-Pyrenees, owe their name to the fact that the first mining operations of any extent, and of comparatively reccnt date, were carried out in the neighborhood of the village of Pierrefitte, which is a branch terminus of the Midi railway. The Pierrefitte mines, however, embrace a wide extent of country and several different concessions, on most of which comparatively little exploration-work has been done. The portion of the property presently to be described is a zone running roughly E—W., over a distance of about 5 miles from the valley of Cauterets to the valley of Estaing, the ridge dividing these valleys being a spur of the main chain of the Pyrenees, and running more or less at right angles to it. According to local tradition, which various indications tend to confirm, these mines are of ancient date, the first workings being attributed to the Romans, who are supposcd to have sought not only the lead but also the silver which is contained in the ore. Old slags have been found in the neighborhood which might well have been produced from the cupellation of lead-ores. These old workings, while of considerable extent at times, do not seem to have extended beyond a depth of 100 ft., even this depth being somewhat exceptional. The old notarial records of the district show that mines were known to exist, and that they were even worked, in the sixteenth century, but since the mines were abandoned (by the Romans or others) considerably prior to this period, very little

Jan 1, 1909

By AIME AIME

TWO weeks ago the writer was lunching in the Engineers` Club in New York with a man who has perhaps the widest acquaintance among engineers of anyone in the country a member of another of the Founder engineering societies. "By the way," lie asked. "who have they nominated for your next president."' "Doctor Becket," I told him- "Oh. that's line," he replied, in a heartfelt tone that rang with sincerity. "I have come in contact with him occasionally and he is just the right type.' And that is the way Dr. Frederick M. Becket impresses everybody. The right type. Most Institute members of the western group of hard-rock minors do not know him, but then they meet him in his swing around the circle next year they will not require a long acquaintance to sense his kindly and outstanding personality, to realize that he is a gentleman in the bet meaning o1 that word, a man of wide sympathies and interests.

Jan 1, 1932

By John W. Cahn

Tile avevage value of the mean curvature of surfaces in a specimen can be precisely delermined by sitrlple measurements performed on random sections or on 1 vojectiotzs of these surfaces. For surjaces enclosing particles, the quanlity is sllown to be velated to the probable tlurrrhev ot particles intevcepted by a random platne and, under certain conditions, to the perimeter of their Projected image and to the increuse in surjace area when the particles grow. Many of the velalionsl~ips are valid for any shape or size of the particles. THE recent growth of the field of stereology or quantitative microscopy is largely the result of the discovery of a limited number of rigorously defined geometrical parameters that can be precisely measured on random sections or projections of a structure without assumption about particle shape.' Such parameters have been the volume fraction and surface area and line length in a unit volume. The present paper introduces the average of the mean curvature of surfaces in a volume, and shows that it can be rigorously measured by counting methods alone. AVERAGE CURVATURE ON A PLANE Consider a curve y = v (x) on the xy plane. The curvature Kp in the plane at any point is given by Kp = (dZy/dx2)/[1 + (dy/dx)2]3/2. The average curvature along the curve may be defined as Kp = (1/L) fKpdl |1] where dl = [(dx)' + {dy)2]1/2 is the length of an element of the curve and .(dl = L is the total length of the curve. The integral on the right-hand side of Eq. [l] will be called the total curvature, It is dimensionless and readily evaluated by substituting d = arctan (dy/dx) to give ah which is the change in direction of the tangents to the ends of the curve, Fig. 1. Hence, Kp = (1/L)(?h) [2] It can also be seen that Eq. [2] is applicable in the limit of sharp corners. Even though the curvature is infinite at a corner, f Kpdl remains integrable and equal to the change of angle. The signs of the quantities Kp and dl are arbitrary and, if the areas adjoining the curve are equivalent, there seems to be no compelling reason to fix the signs. For a closed curve, however, it becomes worthwhile to use the signs to distinguish among different types of areas or phases enclosed. For such a closed curve AO = t2r and As a convention, we shall take the direction of the integration along the curve in such a way that the area or phase under consideration (henceforth called a) is kept to the left side of the curve, Fig. 1. Then Kp is positive where the curve is concave and negative where the curve is convex. For a closed curve Ad - +2n if the curve encloses a, and Ad = —2n if the curve is surrounded by a. PLANAR SECTIONS OF THREE-DIMENSIONAL STRUCTURE OF ISOLATED a PARTICLES Consider next a planar section of a microstructure containing particles of a in a matrix. We place no restriction on shape of connectedness of these particles, and begin by considering the curvature of only the boundary between a particles and matrix' Clumps of contiguous a particles are then treated as a single a particle. The two-dimensional section will show in a unit area na simple closed curves enclosing a particles and nh closed curves of holes, in-

Jan 1, 1968

By Myron Rodgers

IN rock- or ore-crushing tests all data, in order to be valuable for study and comparison, should be obtained and tabulated under conditions as uniform as possible. The results of many such tests have no value for comparison, because of incomplete data and the lack of uniform conditions, screens and scale of sizing, etc. The purpose of this paper is to suggest a form of standard specifications which may be developed by the Milling Committee and approved by the A. I. M. E. for rock-crushing tests. It is not intended to discuss any theories of rock crushing. Reports of rock-crushing tests should include the following details: 1. Description of the machine employed (jaw or gyratory crushers, rolls, stamps, tube mills, Chilean mills, etc.). 2. Method and material (timber, concrete, etc.) of foundation. Much power is dissipated in the vibration of poor foundations. 3. Locality from which the rock or ore was obtained, and geological, mineralogical, and physical characters of the material. 4. The power consumption of the machine running with no load and with full load, the unit of power being 1 hp, per 24 hr. 5. The capacity of the machine in tons (of 2000 lb.) per 24 hr. 6. The duty in tons per horsepower-day. 7. The screen analysis of feed and product by the proposed A. I. M. E. standard screen scale. On the foregoing statement, the following remarks are offered.

Jan 9, 1915

By W. Rogers Wade, Alfred Wandtke

The Pilares mine of the Moctezuma Copper Co. is situated at Los Pilares de Nacozari, Sonora, Mexico, about 75 mi. (120.7 km.) south of the international boundary and about 7 mi. (11.26 km.) east of the town of Nacozari de Garcia. It is situated at an elevation of 5000 ft. (1524 m.) in one of the northward trending ridges that form part of the mountain mass that culminates in the Sierra Madre de Mexico. To the east, south, and west, the topography is rugged and diversified; to the north less diversity exists, ranges of mountains rise sharply out of almost level ground and give the basin range structure characteristic of the Southwest. The climate is dry, the average rainfall of 15 in. (38 cm.) being confined almost entirely to the months of June, July, and August. The winter consists of a few days of disagreeable weather when a little snow may fall; the remainder of the year is thoroughly delightful. Vegetation is typical of a semi-arid region. In the canons near the mine, where water flows intermittently, willows thrive; on the northern slopes of some of the mountains and in some of the broader canons pines may even become abundant. The dominant rocks are flows and pyroclastics which are cut by dykes, stocks, and batholiths. The mountain just west of Nacozari is, in part, composed of limestone of an unknown age which occurs as a syncline and is undoubtedly a part of a prevolcanic land surface. Overlying the limestone and faulted against it, are the volcanics; cutting the limestone is a coarse biotite granite. Whether the granite is older or younger than the volcanics has not been definitely established. No attempt has been made to differentiate the rock types of the volcanic~, of which there are exposed 3000 ft. (914 m.) in thickness of basic and acid flows (andesites, latites, and rhyolites) and andesite and latite tuffs and breccias. The latite breccias, the youngest of these volcanic~, cover the highest mountains in the immediate vicinity. The

Jan 1, 1920

By William Marsh Baldwin

THE ROLLING OPERATION proper is applied to metals and alloys not only in the production of flat products but also in the production of shapes, rods, wire and even in specialized forms in the production of tubes. The present discussion of rolling copper and copper alloys will be [ ] limited to a consideration of rolling flat products such as strip, sheet, foil, plate, and others. In this case (as in the others listed above), the rolling operation itself is only part of an integrated sequence of operations. In Fig I such a sequence going to make up a brass strip mill is sketched out. It is seen that the rolling opera-

Jan 1, 1948

Article IX of the Bylaws constitutes the basic instructions to the Nominating Committee The first duty of the Nominating Committee is to select a candidate for Director and President-elect It is desirable that the successive Presidents from year to year be men of differing professional interests so selected that over a period of years each major group in the Institute will be represented in the Presidency a number of times bearing some reasonable relationship to the numerical strength of that group in the Institute In Section 2 of Article IX it is stated that "a sufficient number of Directors be selected on the basis of geographical districts so that each district will have at least one representative" These districts, as now established, are shown in the accompanying map There are ten districts including the New York metropolitan district Each of these districts is entitled to one Director, except the metropolitan district which is entitled to six Each year each district, the term of whose officially recommended Director expires, shall suggest a candidate and if desired an alternate candidate to the Nominating Committee to fill the vacancy If a candidate and an alternate are suggested they should preferably have different Divisional or Branch affiliations The Chairmen of the Sections In the district shall constitute a committee to select the candidate or candidates The Sections shall rotate the chairmanship, as shown in the Appendix to this instruction It is desirable that in filling a quota vacancy in any district, the selection be made from the name or names suggested by the district

Jan 1, 1952

By Dwight Farnham

Description of Quarry THE shale used at the Renton plant of the Denny-Renton Clay Coal Co., for the manufacture of vitrified paving brick occurs in a hill rising from 200 to 300 ft. above the level of the valley in which the plant is situated. The shale deposit, which is of unknown thickness pitches about 10° to the southeast. The 150-ft. face worked extends approximately east and west, so that the clip, as shown by the photograph, is to the left and into the hill. The shale is overlain with about 50 ft. of gravel, 70 ft. of clay, and 30 ft. of mixed loam and gravel, making altogether from 125 to 150 ft. of overburden. Disposal of Overburden The overburden is removed by sluicing. For this purpose a No. 2 Joshua Hendy giant is used, throwing a 12-in. stream', and having 60 lb. pressure at the nozzle. The water is drawn through an 8-in. pipe from Cedar river, about 1,000 ft. distant, by means of a Worthington four-stage centrifugal pump, direct connected with a 100-h.p. motor placed just south of the factory, and 1,500 ft. from the nozzle This plant handles the material satisfactorily to a height of about 75 ft. above the level of the top of the shale. When the higher levels are worked, an auxiliary plant consisting of a four-stage Byron Jackson centrifugal pump with a 100-h.p., belt-connected motor, is thrown into the system. This plant is situated on top of the shale and can be discerned at the extreme right of the trestle work in Fig. 1.

Jan 9, 1914

By Robert B. Bossler, Parke A. Dickey

The presence of connate water in oil sands is of far greater practical significance in secondary oil-recovery operations than it is in primary operations. The percentage saturations of oil, water, and gas in a depleted field determine whether it will be economically possible to recover oil by secondary methods, and whether water-flooding or gas-driving, or either, will be successful. It is suggested that economic recovery of oil by secondary water-flooding can occur only when a rich bank of oil is formed by the encroachingm water. If the sand has a greater effective permeability to water than it has to oil before flooding, a bank will not be formed, and water-flooding will not be successful, although gas-driving may be. Published results of laboratory work indicate that the effective permeability of a sand to oil and water depends primarily on the saturation of the sand by these phases. They also indicate that a small difference in relative saturation produces a large difference in effective permeability to the phase in question. There thus exists a critical range of saturations, wherein a small change in oil and water content of the sands will make water-flooding possible or impossible. In gas-drive operations the water saturation is less critical but no less important. The presence of connate water in a sand increases the proportion of the residual oil that may be recovered by gas drive. Sands containing oil saturations too low and water saturations too high to make water-flooding possible can often be subjected to gas drive with economic recovery of oil. The results of laboratory work on test samples that do not contain water cannot be applied to normal field operations. More tests on cores containing water as well as oil are desirable, and the improvement of coring technique is necessary. However, sufficient data are already available to enable an operator to use core data intelligently in estimating the chances of a secondary oil-recovery program. Introduction In recent years laboratory work has led to a much better understanding of the principles of oil-reservoir performance. The general principles of the expulsion of oil from sandstone by gas or water were developed by geologists of the Second Geological Survey of Pennsylvania in the 1870lsl but only recently has the mechanism of gas or water drive been intensively investigated. Most published articles have large the facts established in the labora tory to the primary production of oil from flush fields- This Paper is not based on any new observations, but is an attempt to apply some of the conclusions obtained in the laboratory and described in the literature to the recovery of oil from depleted pools by secondary methods. One of the most important factors that determine whether or not a secondary-recovery operation is economically successful is the ratio of injected fluid to oil recovered. This ratio may be expressed as the over-all or cumulative gas-oil ratio if gas is the driving medium, or water-oil ratio if water is the driving medium. Recent theoretical and experimental work has shown that the relative amounts of

Jan 1, 1944

By Parke A. Dickey, Robert B. Bossler

The presence of connate water in oil sands is of far greater practical significance in secondary oil-recovery operations than it is in primary operations. The percentage saturations of oil, water, and gas in a depleted field determine whether it will be economically possible to recover oil by secondary methods, and whether water-flooding or gas-driving, or either, will be successful. It is suggested that economic recovery of oil by secondary water-flooding can occur only when a rich bank of oil is formed by the encroachingm water. If the sand has a greater effective permeability to water than it has to oil before flooding, a bank will not be formed, and water-flooding will not be successful, although gas-driving may be. Published results of laboratory work indicate that the effective permeability of a sand to oil and water depends primarily on the saturation of the sand by these phases. They also indicate that a small difference in relative saturation produces a large difference in effective permeability to the phase in question. There thus exists a critical range of saturations, wherein a small change in oil and water content of the sands will make water-flooding possible or impossible. In gas-drive operations the water saturation is less critical but no less important. The presence of connate water in a sand increases the proportion of the residual oil that may be recovered by gas drive. Sands containing oil saturations too low and water saturations too high to make water-flooding possible can often be subjected to gas drive with economic recovery of oil. The results of laboratory work on test samples that do not contain water cannot be applied to normal field operations. More tests on cores containing water as well as oil are desirable, and the improvement of coring technique is necessary. However, sufficient data are already available to enable an operator to use core data intelligently in estimating the chances of a secondary oil-recovery program. Introduction In recent years laboratory work has led to a much better understanding of the principles of oil-reservoir performance. The general principles of the expulsion of oil from sandstone by gas or water were developed by geologists of the Second Geological Survey of Pennsylvania in the 1870lsl but only recently has the mechanism of gas or water drive been intensively investigated. Most published articles have large the facts established in the labora tory to the primary production of oil from flush fields- This Paper is not based on any new observations, but is an attempt to apply some of the conclusions obtained in the laboratory and described in the literature to the recovery of oil from depleted pools by secondary methods. One of the most important factors that determine whether or not a secondary-recovery operation is economically successful is the ratio of injected fluid to oil recovered. This ratio may be expressed as the over-all or cumulative gas-oil ratio if gas is the driving medium, or water-oil ratio if water is the driving medium. Recent theoretical and experimental work has shown that the relative amounts of

Jan 1, 1944

By Robert T. Ault

The nature of fracture in unnotched tensile and notched tensile sheet and round specimens and V -notched and precracked Charpy-type sheet specimens of both wrought stress -relieved and re-crystallized molybdenum was investigated over the temperature range of -78° to 300°C. The sharp rise in fracture stress, for unnotched tensile samples, as the temperature is increased above the brittleness transition temperature (Tb), is found to be a result of an increase in flow stress due to plastic constraint and an increased strain rate which results from the onset of necking at Tb . Quasi-brittle fracture in notched tensile samples is found to occur when the tensile stress at the elastic-plastic interface, beneath the root of the notch, reaches a maximum critical value, which is independent of test temperature over the range from —78° to 25°C, but dependent on microstructure. In the temperature range between 150° and 300°C, unnotched tensile and notched tensile samples alike are found to fracture by a ductile fibrous tearing process which is discontinuous in nature, as a result of the competition between the processes of tearing, through continued plastic flow, and local work hardening. Results from the V-notched and fatigue-cracked Charpy-type impact tests demonstrate that crack initiation is the governing factor in the low-temperature (-78° to 25°C) fracture process for molybdenum. In recent years, there has been considerable interest, and a commensurate number of investigations, concerning the duc tile-to-brittle transition in refractory metals. There has not developed, however, a satisfactory explanation for the uniaxial tensile fracture-stress transition which accompanies the well-known ductility transition. This matter therefore warranted investigation. In a similar manner, the increased importance of notched tensile strength values in evaluating materials and in design criteria requires a better understanding of the factors which control the fracture behavior of notched tensile samples. In a previous investigation1 of the nature of initial yielding and fracture in notched sheet molybdenum at room temperature, it was suggested that plastic constraint was the controlling factor in governing the fracture behavior of notched samples. The final portion of this investigation was concerned with the fracture toughness of molybdenum. Of particular interest was the comparison of effective surface energies for fracture in V-notched samples with fatigue-cracked, Charpy-type samples in order to ascertain the relative importance of the initiation and propagation phases of the fracture process. MATERIALS AND TEST PROCEDURE Sheet tensile, notched tensile, and V-notched Charpy specimens were prepared from 50-mil, stress-relieved molybdenum sheet.* Half of these specimens were vacuum-annealed for 1 hr at 1200°C and 7.5 x l0-5 Torr and furnace-cooled to produce a relatively uniform grain size of 0.30 mm diameter. Round notched and unnotched tensile specimens were prepared from warm-rolled and swaged 5/8-in.-diam bar.* These specimens were vacuum-annealed for 1 hr at 1350°C and 5 x lom5 Torr and furnace-cooled to produce a grain diameter of 0.11 mm. Material analyses in ppm were: C N O H Sheet 290 10 4 1 Bar 50 30 30 2 The unnotched tensile sheet specimens had a 1/4-in. gage width and a 1-in. gage length. The unnotched tensile round specimens had a 9/32-in. gage diameter and a 1-1/4-in. gage length. The sheet and round notch tensile specimens are shown in Fig. 1. All of the notched tensile specimens tested were tandem-notched in order to study the location and mode of fracture initiation. The tandem-notched specimens were carefully machined so that the largest variation in notch depth on a single specimen was 0.001 in. Thus, when fracture occurs, the extent of plastic deformation that exists in the un-fractured notch section is that which exists just prior to fracture. All of the tandem-notched sheet specimens were electrolytic ally polished and chemically etched prior to testing. The V-notched Charpy-type specimens machined from the 50-mil sheet material had the standard dimensions of 2.125 in. long, 0.394 in. deep, and a 0.010-in. root radius. The unnotched tensile and notched tensile tests were conducted over the temperature range of -78° to 300°C, in a 10,000-lb Instron Universal Testing Machine, at a constant crosshead speed of 0.020 in. per min. The V-notched Charpy-type

Jan 1, 1964

By C. Hertzler

The difference of means of milling characteristics by rock and ore type is tested in a statistical manner in the paper. The null hypothesis being tested is that the sample means of two different populations are equal. It is assumed that the null hypothesis is true when performing the test. Because of this, acceptance of this hypothesis leads to the conclusion that the sample means of the two different populations are equal (or there is no significant difference between the sample means), not that the samples come from the same population, as the author asserts. Rejection of the null hypothesis leads to the conclusion that the sample means of the two different populations are not equal. A P value for this test is reported in Table 2 and is incorrectly identified as the probability that the two samples came from different populations. Actually, what was recorded was 100(1 - p) where p is the usual p-value. The usual p-value measures, on a scale of zero to one, the extent to which the data agree with the null hypothesis. It is the probability of observi" a value of the test statistic (Z score) that is at least as contradictory to the null hypothesis as the one computed from the sample data (McClave and Dietrich 11, 1982). The author makes no mention of the fact that were these tests to be conducted together, the chances of determining that the null hypothesis is not true when it is really true are increased considerably (Snedecor and Cochran, 1980). This is a multiple comparisons problem and should be dealt with accordingly. The usual methods involve adjusting the level of the individual tests. Table 2 reports an incorrect 100(1 - p) value in the comparison of concentrate grades for other rock types with .30 to .69% Cu vs other rock types with .70 + % Cu; 86% should be 98.6%. Although the article can be criticized for poor data presentation and discussion of that data, the point the author makes regarding the use of these statistics in the ore reserve estimation process is well taken. It does not appear that inaccuracies in the statistical interpretations have hindered that usefulness.

Jan 1, 1985

By Ward C. Smith

The industry of producing and processing boron compounds is called the borax industry because the chief product is borax, the decahydrate of disodium tetraborate. For the same reason, it is common to speak of borax mining. Reference to borate mining also is common, and while appropriate where it emphasizes the diversity of borate minerals that are mined in various countries, it is rather unsatisfactory where used in a general sense, because it seems to exclude the important production of borax from brine at Searles Lake, California, and of boric acid from steam vents in Tuscany, Italy. The terms "boron industry" and "boron mining" might seem more comprehensive, but are little used, and this is fortunate because they would be misleading-the element boron is manufactured only in small amounts for special uses, and it is not found free in nature. In most occurrences, boron is combined with oxygen and is in a borate or borosilicate material. The history of the modem borax industry starts with the introduction into Europe of borax from Tibet in the 13th century, about the time of Marco Polo, if not actually by him. The discovery that borax has unique value as a flux in metal soldering and ceramic glazing must have been made at some unknown time much earlier. As a rule, any mineral that has been used so long that its early history is lost must occur in deposits that are easily recognized and worked, and this is undoubtedly true of borax in Tibet. According to meager accounts,9 the borax occurs there in arid mountain basins as surficial crusts that coat the ground about thermal springs and seeps of mineralized water, and as coarser crystals in the bottom muds of shallow pools and lakes. Much the same essential features of surface exposures and minerals easy to recognize and recover characterize most of the deposits later found and worked elsewhere. The borax industry at the present time is faced with rising demands for its products, and consequently is increasing its productive capacity and appraising its borate resources.18 The areas that contain the known borate deposits are most likely to yield additional production, hence their distribution in the world is of interest, and is summarized later in this chapter. Mineralogy The mineral raw materials used by the borax industry include various borates mined in several countries, borax extracted from brines at Searles Lake in California, and boric acid extracted from the steam of vents in Tuscany in Italy. The hydrated borates[$] of chief commercial importance are listed in Table 1, which also shows their chemical composition. The properties of only the four most important borates are summarized here, but detailed descriptions of the borates and the minerals commonly found with them can be found in mineralogy textbooks.41 Ulexite generally forms clusters of silky fibers rather than large individual crystals. A

Jan 1, 1960

By J. D. Hanawalt, W. H. Gross

Magnesium has long been known as the lightest of our engineering metals. This metal, silvery white in color, has a specific gravity of only 1.74. Aluminum, the next lightest structural metal, is 1 ½ times heavier; zinc is 4 times heavier; iron and steel are 4 ½ times heavier; and copper and nickel are 5 times heavier. Magnesium does not occur in the free state but is very abundant in nature, constituting 2.5 pct of the earth's crust in the form of various ores. It is the third most abundant structural metal, being exceeded only by iron and aluminum. Magnesium is unique, however, in that in the form of magnesium chloride it also exists in the oceans. Sea water is the source most widely used for production in the United States but magnesium is also commercially produced from magnesite, dolomite, and other ores as well as from certain inland brines. The vast quantity of magnesium existing in the waters of the oceans can be visualized when it is realized that the removal of one hundred million tons per year (the approximate annual steel production in the United States) for a million years would reduce the magnesium content of sea water only from 0.13 to 0.12 pct, providing no more magnesium had washed into the sea in the meantime. Not only is magnesium potentially very abundant but it is in addition a very versatile metal and can be shaped and worked by practically all methods known to the art of metal working. It can be cast by sand, die, and the various permanent-mold methods;

Jan 1, 1953