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Jan 1, 1941

By R. J. Greaves

High-resolution seismic reflection profiling can be used to evaluate detailed structural and stratigraphic features of coal prospects. Since most coal prospects are relatively shallow, less than 1000 m (3000 ft) deep, high sampling rates in space and time can be used effectively to improve vertical and lateral resolution of seismic data. The case study presented here shows how seismic data was used to evaluate the Wyodak coal at a prospective coal gasification site. The data were used to map the detailed structure and thickness of the coal and to search for lateral discontinuities, such as pinchouts and faults. An important find was a paleochannel cutting across the base of the coal seam, which was later confirmed by drilling.

Jan 1, 1986

By J. C. Norman

Jan 1, 1985

By Leonard A. Wood, A. G. Winslow

Subsidence has occurred in several areas of the upper Gulf Coast region of Texas, although in most cases this is not evident without precise instrumental leveling. As referred to in this report, the region com- prises about 7200 sq miles of the Gulf Coastal Plain and includes all or parts of the following counties: Harris, Fort Bend, Waller, Brazoria, Galveston, Liberty, Chambers, Orange, and Jefferson (Fig. 1 ). Topographic relief is low, ranging from sea level at the Gulf of Mexico to 300 ft or more in northwestern Harris County.

Jan 10, 1959

By Franklin H. Sharp

The operation of the Magmont Concentrator located on the New Lead Belt of Southeast Missouri is described. Ore characteristics affecting lead-copper-zinc separation are enumerated, and the cur- rent methods of separation are detailed.

Jan 1, 1976

By A. K. Gangopadhyay, J. J. Moore

The effect of grinding media composition, mineral type, and slurry environment on the wear rate of various grinding media (balls) are discussed. Sufficient wear data have been obtained and correlated. Modes of wear were determined from examination of the ball surfaces using scanning electron microscopy. Five modes of wear have been identified to be operative under certain slurry conditions for the various ball compositions studied.

Jan 1, 1986

By Barry H. G. Brady

A state of stable equilibrium is required in a mine structure to ensure that small increases in the mined void are accompanied by only small displacements of the rock mass. Methods of determining the stability of equilibrium in a rock mass currently require a geometrically regular stoping layout, and introduce a number of simplifying assumptions. The method reported in this paper models the mine near-field using Finite Elements, and the far-field using Boundary Elements. The stability of equilibrium in the modelled structure can be assessed directly from the value of selected principal minors of the global stiffness matrix.

Jan 1, 1981

By W. C. Kerr

When Agassiz and his party of geologists commenced their exploration of the interior of Brazil and the Amazon region, one of the first and, to the last, one of the most novel and striking phenomena which met them everywhere was the great depth of decomposed or partially decayed rock in situ, which mantles, and for the most part conceals, the underlying strata. The same facts strike all geological observers from the North who happen to penetrate the middle and southern latitudes of the Atlantic States. In North Carolina, e. g., the entire middle and western regions, outside of the Quaternary clays, sands, and gravels of the East,—that is, all that portion of the State occupied by the Archæan and Mesozoic rocks,—show everywhere this peculiarity, so new to those accustomed to glaciated surfaces. Not only do the hills and slopes, the mountain chains and

Jan 1, 1880

By David A. Summers, Steven McGroarty

The last ten years has witnessed the change in water jet cutting studies, on rock, from laboratory testing to prototype use of field equipment. Unfortunately, while equipment and technological developments have occurred, the understanding of the exact mechanisms of water jet erosion have been less well developed. Commonly, theoretical evaluations have used the uniaxial compressive strength of the target rock as the major parameter of rock erosion resistance . It is considered that the structural properties of the rock, and most particularly, the flaw density and heterogeneity of the rock are much more important parameters. This is demonstrated and discussed. Locating the jet and target under water and pressurizing the containing vessel makes it is possible to induce cavitation in and around the water jet and create a much slower erosion process.

Jan 1, 1982

By C. Harries

The mechanism of blasting and the effect that blasting has on rock properties including the generation of new cracks and the opening of existing joints is discussed and compared with changes in seismic velocities. .Knowing the extent of blast induced damage and the overall stable slope angle it is shown that it is possible to design blasting so as not to induce any damage behind the toe of the blast area. Practical methods of blasting to meet this criterion and the results of these blasts are then discussed.

Jan 1, 1983

By John E. Gale

Seven, 15 cm diameter, cores of gneissic granite, four containing induced fractures and three containing natural fractures all oriented normal to the core axis, were tested in an uniaxial compression mode over a range of 0 to 30 MPa. At given normal stress increments, over two or three loading and unloading cycles, the flowrates and changes in fracture aperture were measured. The induced fractures gave lower initial (at low stresses) and lower final flowrates (at maximum stress) than the natural fractures. Both types of fracture exhibited permanent fracture deformation between loading cycles as well as highly nonlinear, with distinct hystersis, loading and unloading flowrate-stress curves. A significant finding of this stud is the breakdown of the cubic law for fracture flow in induced fractures subjected to normal stresses greater than 20 MPa, with the breakdown occuring at much lower stresses in natural fractures.

Jan 1, 1982

ON THIS page is a photograph of a machine that has played a key role in the recent history of Kennecott's Ray mine, situated in the Mineral Creek District, Pinal County, Arizona. It is a huge, rugged, Diesel-powered, rubber-tired truck, having a capacity for carrying fifty tons of ore. It has, to a substantial degree, revolutionized the business of moving broken rock by cutting down both maintenance and operating costs. From 1911 until the end of 1954 Ray had produced 79,000,- 000 tons of ore by underground block-caving. However, in 1947 [ ]

Jan 1, 1957

By V. Miller

Highly variable milling procedures within a geologically complex porphyry copper deposit owned by Kennecott Corp. in Nevada made it necessary to estimate copper recovery and concentrate grade in areas where actual test data was lacking. Estimation was made by first determining the relationships between desired metallurgical properties and the ore's petrology-copper mineral type, rock type, and copper grade. This relationship was then combined with previously estimated rock type, mineral type, and copper grade data in the mineral block model to predict milling properties.

Jan 1, 1985

By E. H. Ahrens

This paper deals with the responsibilities of an operating geologists and the relationship of operations to exploration. It should be of interest to those soon to enter the profession, those new to mining geology and as a review to more experienced geologists. Subjects discussed include detailed geologic mapping, sampling, core logging, assaying, selection of proper map scale, posting geological and assay data, section preparation, identification of ore controls, delineation of development drill targets and geologic hazards, models and the very important topic of salesmanship. Methods and ideas, proven valid in vein, pyrometasomatic replacement and porphyry copper deposits are presented. Hopefully, these will smooth the path for new members of our profession.

Jan 1, 1984

By Reynold Q. Shotts

Data are presented which show that fractions of varying densities from the same coals are oxidized at different rates by nitric acid. From oxidation data, the approximate quantity of "bright" and "dull" components may be calculated. Definite relationships between oxidation rate and rank are shown for density fractions from at least two bituminous coals.

Jan 8, 1950

By Francis T. Christy

One aspect of ocean mining that is frequently overlooked in discussions is the problem of establishing some form of legal control over the seas. Much of the discussion centers on mining in territorial waters, which are controlled by the various countries according to the Geneva Convention on the Continental Shelf, and perhaps by political subdivisions of countries such as the individual states of the U.S. But as technology improves and the mining of deeper waters becomes feasible, the problem of rights outside the continental shelf and territorial waters becomes a significant factor for anyone expending the time and capital for development. Several schemes are possible for regulating ocean mining but as yet none have been instituted, except what might be termed the "wait and see" approach. Even some of the coastal states in the U.S. have no regulations governing mining in the territorial waters under their jurisdiction. Until some regulation is formulated, there may well be little development in ocean mining due to the high risk of capital involved, both with respect to companies wishing to invest their own funds and financial institutions funding a venture to develop offshore mineral deposits.

Jan 7, 1968

By E. Richard Randolph, Rolland L. Blake, Stanley H. Ward, Gerald J. Anderson

During the last 30 years the inductive electro- magnetic method has been used chiefly in the search for massive sulphide mineralization. This application has met with varying degrees of success and in recent years has resulted in discovery of several large orebodies. Little has been written concerning its use in exploration for soft iron ores, but one of the present authors has reported on experiments with massive magnetic deposits. To augment the exploration tools available to geologists in delineating iron orebodies, Cleveland-Cliffs Iron Co. and McPhar Geophysics Ltd. undertook in 1953 to apply the inductive electromagnetic method to Cleveland-Cliffs properties in the Lake Superior region. As a result of this project, equipment has been developed that enables simultaneous transmission of two audio frequency waves, and the field technique and interpretative procedure involved have furthered exploration in the district significantly.

Nov 1, 1955

By Thomas Connolly

The Homestake Mine is situated in the northern portion of the Black Hills of South Dakota in a series of steeply dipping and highly folded Precambrian Rocks. The ore bodies are localized along plunging anticlinal and synclinal folds which are locally called "ledges." The gold bearing ore is confined mainly in the Homestake formation which is an iron-magnesium carbonate series of rocks. The individual ore bodies are pipe or lense-shaped zones which plunge 30º to 75º from the horizontal. These ore bodies range from 10 to 100 feet wide and 50 to 400 feet along the strike. Gold values are erratically distributed in a gangue consisting of cummingtonite schist, sideroplesite schist, quartz, pyrrhotite, arsenopyrite, chlorite schist and ankerite. Usually the ore bodies dip at 70° to 80º and often have folded shapes like "fish hooks" or "troughs." Ore grades must be determined by extensive sampling and all mining is based on assay control.

Jan 3, 1974

Jan 1, 1942

By Frank S. Hurley

To comply with the California Mine Safety Orders pertaining to transportation of mine workers over mine railroads, the management of the New Idria mine in San Benito County, Calif., designed special man-cars. The new regulations, dated October 1958, make it mandatory for mine man-cars to be designed for carrying five or more men to and from the mine workings. At the New Idria mine, largest single producer of mercury in the U.S., each shift normally employs about 70 men. However, with the possibility of a future increase in the work force, seven man-cars were constructed with a total carrying capacity of 84 men. The general design of the mine man-cars was dictated by safety regulations plus the physical characteristics of the mine-low headroom, limited side clearance in haulageways, and track irregularities due to ground swells. The cars measure 10 ft long, 44 in. wide, and 50 in. high and were built at an average cost of $450 per car. All assembly work was done at the mine site.

Jan 7, 1960