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By David White

ATTENTION has been given to the sources and supply of the raw vegetal matter and. the conditions of its submission to the process of sedimentation. An original and most valuable review has been made of the more important or significant chemical compounds originally contained in the organic debris, and of the biochemical changes-undergone by the latter during deposition. Consideration also has been given to the factors controlling the selective biochemical decomposition, in whole or in part, of :this debris, and the deposition, as, sediments, of the undecomposed plant structures and compounds, together with more or less of the so-called "ulmic," or "humic," organic decomposition products in colloidal solution.1 BIOCHEMICAL CHANGES END IN PEAT FORMATION The biochemical process terminates in the peat stage of coal formation, and with the cessation of this process organic sedimentation is completed. All subsequent changes result from geological causes and conditions. The deposits are in the form of peats of different types, organic muds, oozes, etc. They are essentially uncompressed and are wholly unconsolidated, and their water content is great, amounting to over 85 per cent. near the surface of the deposit. Many of the chemical compounds remain as in the once living organisms; others are biochemically broken down and new ones formed.

Jan 2, 1925

By Raymond B. Ladoo

Wollastonite is a calcium metasilicate, with the formula CaSiO3; containing theoretically 48.3 pct CaO and 51.7 pct Si02. It is one of many natural and synthetic silicates with varying CaO/SiO2 ratios, with and without water of crystallization. While it is a very common mineral, deposits of sufficient size and purity to be of commercial interest are unusual. There is only one producer (1958) of wollastonite for industrial use in the United States, Godfrey L. Cabot, Inc. at Willsboro, New York. There has been a small production of surface material for ornamental use from near Blythe, California. Carload tests have been made on California wollastonite for making mineral wool and a commercial plant for this purpose was projected in 1957. Properties Wollastonite is monoclinic and commonly occurs in masses or aggregates of bladed or needle-like crystals. It has a perfect cleavage parallel to the long prismatic axis. It is rather brittle and some types grind easily to a very finely fibrous product, but other types, due to interlacing of fibers, are tough and difficult to grind. Mobs hardness is 4.5 to 5; specific gravity 2.8-2.9; index of refraction 1.616 to 1.631; melting point 1,512°C. Color when pure is a brilliant white, but when less pure it may be gray or brown. Luster is vitreous, transparent to translucent. Common mineral associates are garnet (several varieties), diopside, calcite and quartz. The nature of the mineral impurities determines to a large degree the commercial value of a deposit. At Willsboro, New York, the impurities consist chiefly of iron garnet and iron diopside which are both magnetic and so are easily removable by magnetic separation, yielding a nearly theoretically pure product. Some deposits in California contain calcite and quartz which cannot be removed cheaply, thus limiting market possibilities. Occurrence Wollastonite is a contact metamorphic mineral occurring in most places within or associated with impure limestones. The deposits at Willsboro, New York1,2,3,5 consist of two or more beds dipping 15-50°E and striking NW-SE. The main bed, 30 to 70 ft thick, may be traced on the surface for at least 2 ½ miles. In this belt, the Pre-Cambrian Grenville limestone has been injected and partially replaced by the more liquid portions of an anorthositic magma. Buddington and Whitcomb3 have described the rock as "Mixed gneisses, pyroxenite and garnetiferous gneisses and skarns." Prospecting revealed the wollastonite at ten different places in the belt, overlain in most places by a garnet rock. Diamond drilling has proven several million tons with probable reserves around 15 million tons. Interbedded with the wollastonite are beds of garnet from a few inches to several feet in thickness. In the wollastonite ore itself the chief and almost only associated minerals are garnet (mostly almandite but some andradite and grossularite) with small amounts of green hedenbergite. Inasmuch as the almandite and diopside are magnetic they are easily separated from the wollastonite in high intensity magnetic separators. If grossularite should occur in quantity other means of separation would be needed. Wollastonite has been reported at 35 localities in California12 but only those in the Big Maria and Little Maria Mountains, 16 to 20 miles north of Blythe, Riverside County, are

Jan 1, 1960

A SERIES of papers on strategic and otherwise important mineral products was prepared some ten years ago under the joint auspices of the Committee on Foreign and Domestic Mining Policy of the Mining and Metallurgical Society of America and the Committee on Industrial Preparedness of the American Institute of Mining and Metallurgical. Engineers. These papers were later published in a joint volume entitled International Control of Minerals (1925). Amongst them was one on manganese. The Subcommittee on Manganese prepared its paper in two forms. One was intended for inclusion with the series above referred to and approached its subject more particularly as an international problem. The other dealt more definitely with manganese as an element in the problem of national defense. This last was first written under date of January 24, 1924 as a confidential report, for and at the request of the War Department. It was later released and published, in slightly modified form, as a separate pamphlet by the Industrial Preparedness Committee of the American Institute of Mining and Metallurgical Engineers. After the lapse of eight years, in view of the vital position of manga-nese in the problem of industrial preparedness against a war emergency, the War Department made a request to have the conclusions of 1924 reviewed and brought up to date. To comply with this request the manganese subcommittee was reconvened (with a somewhat changed personnel) and exhaustive studies were once more made of the entire subject of manganese. A new report, with specific recommendations, was submitted to the War Department in February, 1932. This second report is now herewith released for publication. Certain specific conclusions and recommendations as expressed to the War Department are omitted. Otherwise the report stands as prepared and submitted by the manganese subcommittee of 1931. The members of this committee were: C. Minot Weld, Chairman, R. C. Allen, Arthur S. Dwight, J. W. Furness, D. F. Hewett, Reno H. Sales, Theodore Swann and Scott Turner. ARTHUR S. DWIGHT, Chairman, Committee on Industrial Preparedness.

Jan 1, 1933

By George S. Rice

Ten years ago: October, 1914, the author had the privilege of giving an illustrated address on investigations of coal-dust explosions1 to this Institute at one session of its fall meeting in Pittsburgh, Pa,. On the following day, the members had the opportunity of seeing a large-scale explosion test at the Experimental Mine near Bruceton, in which the explosion was made to follow a predetermined path by means of rock-dust barriers of various types, which had prevented the explosive waves from reaching the outlets of the mine by the shortest paths.2 There was also shown a ((home-made" rock-dusting machine discharging the dust from a flexible nozzle, and a cement gun operated for the quick erection of a fire or ventilation stopping, such as might be put up after an explosion. Following that paper, there was presented a paper by J. Taffanel, Director of the Lìévin testing station in the Pas de Calais, which reviewed the French coal-dust investigations.3 A paper4 by Howard N. Eavenson contains lists of explosions that occurred in North America and Great Britain, from early in the 19th century to 1912; in France to 1903, and Belgium to 1909. Although explosions still occur, we are hopeful that we have entered a happier freedom from these visitations, as the result of increased knowledge of the causes and means of prevention. Looking back over coal-dust investigations, there appear to have been periods of advance and of stagnation. Coal-dust Investigations From the earliest times of coal mining, which chiefly affected Great Britain as the first nation to take up coal mining on a large scale, to the beginning of the 19th century, no one thought of coal dust as an explosive agency; firedamp was the cause dreaded. It was believed, when Sir Humphrey Davy invented his safety lamp in 1815, that a solution had been found for the prevention of mine explo-

Jan 1, 1925

By Dean W. Lynch

Arizona: The San Xavier Indian Reservation mine is located approximately 2 ½ miles northwest of Asarco's Mission Mine southwest of Tucson. The company plans to produce oxide and copper-bearing siliceous ore at this operation, construction of which is scheduled for completion in 12 months. Asarco also plans a copper leaching and iron precipitation plant at its mine. The plant will leach 4000 tpd of oxide ore using sulfuric acid produced at the company's acid plant now under construction at Hayden. Copper precipitates will go to the smelter at Hayden. A drilling program at the Sacaton copper prospect in Pinal County, has disclosed two porphyry copper deposits. One deposit, mineable by surface mining, has approximately 17 million tons of material averaging 0.80% Cu. A deeper deposit suitable for under- ground mining has approximately 12 million tons averaging 1.5% Cu. Although Asarco intends to place this property in production, no startup date has been determined.

Jan 1, 1970

Why should I pay $8.50 an hour for dealer repairs when my own mechanics work for $3.50?" The numbers vary, but that's the argument most contractors use to justify doing their own repairs. They don't realize it, but they're probably losing big money. For instance, it takes nearly a quarter of a million dollars in tools alone to equip a shop comparable to an average equipment dealer's facilities. A contractor must buy a lot of expensive, specialized tools he seldom uses, or else settle for the inefficiency of having repairs done by his mechanics with relatively unsophisticated tools. His building soaks up money in rent, maintenance insurance, taxes. His mechanics demand good wages. It even costs money when mechanics aren't repairing equipment. Mechanics get full wages for slack periods and cleanup time, too. This doesn't count as service manhours, but it's still part of the total repair cost. To help contractors uncover these hidden expenses and find out the true cost of owning a shop, some equipment dealers have devised a do-it-yourself "shop cost analysis form."

Jan 1, 1970

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

By Eugene N. Cameron

Pegmatites of these areas have become important sources of beryl and lepidolite and have yielded cassiterite, columbite-tantalite, and other minerals. Examination of about 60 of these pegmatites leads the author to question the opinion of earlier investigators that the concentrations of beryl, lepidolite, and columbite-tantalite found have mostly formed by hydrothermal or pneumatolytic replacement of previously formed quartz-feldspar pegmatites. The author concludes, on the contrary, that present knowledge of the occurrence of minerals in zoned pegmatites can be applied to prospecting and mining of pegmatite deposits in these two areas of South West Africa. PEGMATITES occur in abundance in certain areas of South West Africa and in adjacent parts of northern Cape Province in the Union of South Africa. Some of the pegmatite deposits were prospected before World War I, and intermittent mining was done during the period between the two World Wars. The deposits of the Jooste lithium mines became an important source of lepidolite, and beryl, columbite-tantalite, wolframite, and other minerals were produced. Since World War II prospecting and mining have been carried on vigorously, with the result that South West Africa produced nearly 3000 tons of beryl during 1949 through 1953, together with more than 40,000 tons of lithium minerals, chiefly lepidolite and petalite. Small amounts of tantalite, columbite, and other minerals have also been produced during the postwar period. Most of this mineral production has come from two pegmatite areas roughly outlined in Fig. 1. One is the Karibib-Omaruru area of north central South West Africa. The second is the northeastern part of the Orange River pegmatite area, which extends into adjacent parts of Namaqualand, in northern Cape Province of the Union of South Africa. The writer visited the two pegmatite areas in July 1951. The visit was brief. but it gave an opportunity to compare some of the' pegmatites of these areas with those studied and described in detail by many investigators in the U. S., Brazil, and Canada during and since World War 11.'-l' The writer has attempted to determine, in a preliminary way, whether the concepts of internal structure and distribution of minerals in pegmatite bodies developed out of these studies are applicable to prospecting and exploration of pegmatites in South West Africa. Previous Work In an important series of papers (1929 to 1942) T. W. Gevers, H. I?. Frommurze, S. H. Haughton, G. K. Joubert, and other geologists of the Geological Survey of South Africa described and discussed the pegmatites of the two areas.*-" These works are the principal sources of information on the pegmatite mineral deposits of South West Africa. The investigations showed that in the two areas pegmatites are profusely distributed in pre-Cambrian rocks. These rocks are meta-igneous and metasedimentary units that have been folded and subsequently invaded by younger pre-Cambrian granites and by other igneous rocks. The pegmatites are considered to be genetically related to the pre-Cambrian granites. Pegmatites occur in the granite bodies themselves but are most abundant in the surrounding metamor-phic rocks, a pattern repeated in many pegmatite districts of the world. The origin of the pegmatites and the factors controlling the occurrence of mineral deposits in them were discussed at length by Gevers and Frommurze (1929)" and later by Gevers 14, 15 pp. 41-51, Ref.

Jan 1, 1956

By E. C. Harder

The situation in the United States, at the present time, regarding the supply of manganese ores and alloys of manganese is one of great seriousness and is likely to become increasingly so while the European war continues. The two principal iron-manganese alloys, ferromanganese and splegel-eisen, are indispensable in steel manufacture, being used extensively in the Bessemer and open-hearth processes. Spiegeleisen, the lower alloy, contains between 15 and 25 per cent., and ferromanganese, the higher alloy, between 60 and 80 per cent., of manganese. Besides manganese the alloys contain iron and carbon. On the market ferromanganese is usually quoted on the basis of 80 per cent. manganese, and spiegeleisen on the basis of 20 per cent. manganese. The consumption of ferromanganese has been increasing during recent years at the expense of spiegeleisen, because larger quantities of the latter must be used to accomplish the same purpose with the result that the amount of carbon introduced with it into the molten metal is frequently injuriously great. Manganese ore proper, in the form of manganese dioxide, is used extensively in many chemical industries, especially for oxidizing purposes. It is also used for the manufacture of both wet and dry electric cells and in the manufacture of paints and dyes. The manganese ore used in this country has been derived hitherto from three principal sources: Southern Russia, Southern British India and East Central Brazil. The following tables show the quantity of manganese ore imported from these countries, and (for comparison) the domestic production, during 1912, 1913 and 1914. The imported manganese ore has been used largely in the manufacture of iron-manganese alloys and in addition large quantities of the alloys themselves have been imported, chiefly from Great Britain, Germany and other European countries.

Jan 1, 1917

By C. S. Sivil

To modern civilization the platinum metals are of inestimable value. Their distinctive properties, both physical and chemical, render them indispensable in an age in which the processes of the laboratory are becoming an essential part of the daily life of the world. Generally, their function, though vital to particular processes, is not spectacular, and so remains unknown to all except the operators. Early Methods of Manufacture The properties of platinum were recognized as of prime importance for scientific work at a very early date, probably between 1750 and 1760. The difficulty of making articles from it seemed almost insurmountable, because no means of attaining the temperature necessary to melt it were known at that time. It is true that solid platinum could be obtained by fusing the metal with a more volatile metal such as arsenic, which was subsequently driven off by baking, but such a method, at its best, would give only a very brittle product, which was totally unsuitable for the purposes for which it was intended. Little, if any, progress could be made until it was discovered that platinum sponge, heated to white heat and hammered in an iron or clay mold, would metallize and retain the shape of the mold. This was a process that could not be wholly satisfactory but from it developed the method of pressing the sponge in a mold and forging it at white heat into wire or sheet. At present a somewhat similar process must be used for fabricating articles of tungsten, molybdenum and other metals of high fusing point, as with these metals we face today the same problems that the scientists of the eighteenth century encountered with platinum, but possibly the next significant advance in the metallurgy of these metals will be the devising of means to melt and cast them. TO some extent this method of preparing platinum has survived, particularly in Europe. There are one or two objections to it, but they are not serious, as they can be surmounted with proper precautions. In the first place, the material is spongy and its millions of cavities contain entrapped air. Unless this is removed by thorough forging above 1000" C. the resultant sheet shows blisters. To give such a thorough forging,

Jan 1, 1931

By Betty J. Laswell, Gerald W. Laswell

Rotary drilling in modern open-pit mining is usually considered the lead phase which not only establishes the production rates but frequently limits them. From this viewpoint alone, the drilling phase must be maximized. The drill phase is the step that permits all the other operational phases to function within their design limits. This means that, in most cases, the drill is literally run to destruction to ensure that the shovel will be able to smoothly and consistently load a manageably size muck, the haul trucks can carry a balanced load without having a boulder dropped through the bed, and the crusher can devour constant rock size.

Jan 8, 1978

By Sadao Maruyama

INTRODUCTION Since the big discovery of Kuroko deposits in Kosaka mine, Akita Pref., northeastern Japan in 1959, major Japanese mining companies have been engaged in extensive exploration for the deposits expending large amounts of money. Above all their exploration activities have been particularly fruitful in discovering new deposits in northern Akita Pref. It is estimated that the total ore reserves newly found in the area are at least 50 million tons. Kuroko deposits are the most important ore source of copper, lead and zinc in Japan and have been mined since last century in the said area. Kuroko (black ore) is fine, compact aggregates with sphalerite , glena and barite as principal constituents and chalco- pyrite, pyrite and tetrahedrite as subsequent constituents. The name Kuroko comes from its appearance. It is not rare that total grade of copper, lead and zinc reaches 20 - 30% and the gold and silver content is also fairly good. Accordingly the unit value of the ore is much higher than the ore from other types of deposits. Besides the Kuroko ore, the Kuroko deposits consists of Ohko (yellow ore, massive cupriferous pyritic ore), Keikoh (silicious ore, cupriferous network ore) and gypsum ore. This type of deposit is considered to be not only an important source of base metal but also a source of gypsum and barite. Although the importance of this type of deposit had been commonly recognized, sub-surface nature of the occurrence hampered exploration work. In recent years the improved exploration techniques and increased knowledge of the Kuroko deposits have met with remarkable success in the location of new deposits. This outburst of exploration and dis-

Jan 1, 1970

By T. D. Yensen, N. A. Ziegler

The elements aluminum,' arsenic,2 silicon,3 tin2 and vanadium,~.~ when used in relatively small amounts as alloying elements, seem to have a beneficial effect on the magnetic properties of iron—i. e., they increase the maximum permeability and decrease the coercive force—whereas there are definite indications that boron,5 carbon,6 nitrogen: oxygen," phosphorus16 sulfur6 and titaninum,~ as well as the metals of and adjacent to the ferromagnetic group, nickel,~ cobalt,1° copper," and manganese,% have a detrimental effect on these properties. The effects of calcium4 and magnesium4 are small, if any, while the effect of chromium12 in small amounts is unknown and in large amounts is generally detrimental. WeveR's Classification13 All chemical elements may be divided into three classes based on their effect on the allotropic transformation points of iron. Class 1 contains the nonmetallic elements (except phosphorus) and these lower the A3 point and raise the A4 point. Class 2 contains the common metals and

Jan 1, 1931

By George I. Smith

Jan 1, 1985

By Chauncey L. Berrien

The United Verde Copper Company's mine is at Jerome, Ariz. The orebodies arc of the schist replacement type, the main sulfide mass being a large lens-shaped body approximately 7 acres in cross-sectional area. In general, the mineralization is found along the iron schist contact, with the orebodies extending about 1000 ft. along this contact and varying from a few feet to 250 ft. in width. Three types of ore are mined; schist porphyry and the so-called "heavy" or "massive sulfide" ore. Approximately 50 per cent. of the total tonnage mined at present is of the latter class. A representative analysis of this ore indicates 42 to 46 per cent. sulfur. Because of the high sulfur content, blasting in this ore is an extremely hazardous operation. not only does it endanger the lives of men who may be in the mine at blasting time but it also becomes a potential fire menace when timber is in close proximity to shots being fired in these massive sulfides. The origin of the fires of 38 years ago, embers of which are glowing to this day, may perhaps be attributed to dust explosions due to blasting in the massive sulfides of those early square-set stopes. Dust Explosions Dust explosions in coal mines are a common source of mine disasters. That such explosions may be of common occurrence in metal mines is not generally known, but it is known that metal-mine dust will explode and such explosions have been investigated by the U. S. Bureau of Mines at the Pittsburgh Experiment Station. Samples of "heavy sulfide" ore from the United Verde mine were used in the tests. After studying the results of the tests it was concluded1 that: 1. Dust explosions were initiated in sulfide ore dust in the gallery with a charge of as low as 75 g. of 60 per cent. gelatin dynamite. 2. The exploding dust generated considerable pressure.

Jan 1, 1930

By J. Ruzicka

In creep testing, material is subjected to a constant load, preferably at a constant temperature, and its rate of deformation is measured. The method of loading can be of various types but in this paper only creep testing under tensile load will be considered. The ordinary tensile test is essentially a comparison test in conditions that frequently hear little or no relation to those under which the test material is to be used in service. The purpose of creep tests is to measure the strength of the test material at slow rates of deformation that more nearly approach the rates realized in service. One purpose of this paper is to illustrate that the creep test, in addition to its value as a service test, is superior to the ordinary tensile test as a sensitive tool for the comparison of certain metals in investigative testing. The other purpose is to describe equipment having distinctive features of design that make it especially suitable for such tests. Representative data obtained with this equipment on a group of rolled zinc-base materials are given. These data are compared with those from practical comparison tests of the creep type on weatherstrip fabricated from the same group of materials. The comparison illustrates the value of the fast creep test and of the equipment. The Equipment The creep equipment consists essentially of a tank containing a constant-temperature oil bath in which the creep of 14 specimens, loaded by means of levers, is measured by means of one movable extensometer. Figs. 1, 2 and 3 illustrate its general construction and appearance. Constant-temperalure Oil Balh.—A common constant-temperature bath requiring only one temperature-controlling equipment for a number of specimens was chosen as the best means of fulfilling the requirements of low cost and compactness. In addition, this allows the testing of a group of specimens under identical temperature conditions.

Jan 1, 1937

By Sydney H. Ball

MINERALS used primarily for personal adornment and decorative purposes are called precious stones. To be so prized, the stones must possess beauty of color, must not be too common, and must be hard enough to withstand ordinary wear. If transparent, they must have brilliancy and fire. Almost one hundred minerals have been used as precious stones, the noble gems being the diamond, emerald, ruby, and sapphire; pearls are frequently included by courtesy. These gem stones, however, are sometimes equaled in beauty by fine opals, aquamarines, ourmalines, spinels, chrysoberyls (both cat's-eye and alexandrite), and spodumenes (hiddenite and kunzite). The Greeks, Romans, and medieval Europeans grouped together gem stones according to color and degree of transparency, and only as the niceties of mineralogy began to be known, about a century ago, was it realized how many different minerals have the beauty required of gem stones. Pliny, for example, did not distinguish between rubies and the red varieties of spinel and garnet, although he conjectured that the beryl and emerald were one mineral. GENERAL SURVEY Early man treasured bright colored berries, attractive shells, white teeth of wild animals and brightly colored pebbles, and used them as personal ornaments. In the eastern hemisphere, the earliest stones used were members of the quartz family (100,000 to 75,000 B.C.); then obsidian and amber (50,000 to 25,000 B.C.); the jade minerals, fluorspar and jet (22,000 to 7000 B.C.); turquoise (7000 to 3400 B.C.); lapis lazuli and garnet (prior to 3500 B.C.) ; emerald (2000 to 1800 B.C.) ; sapphire, ruby and diamond (800 to 500 B.C.). Indeed, gem mining is the oldest form of mining, and before any metals were known primitive man recognized about 18 gems and decorative stones. At first he sought them in stream gravels and residual deposits but by 3400 B.C. the turquoise mines of the Sinai Peninsula were operated. This was the world's first important hard-rock mining enterprise. The Afghanistan lapis lazuli mines may

Jan 1, 1949

By Thomas T. Read

Jan 1, 1913

By Robert V. Whitman

INTRODUCTION Ideally, this paper should start by citing examples of slope failures in open pit mines during earthquakes. I do not know of any such examples, although - since my search of the literature has not been exhaustive - such examples may well exist. However, there certainly are many examples of devastating earthquake-induced landslides, and there is no reason why such landslides cannot occur at large open pits. Moreover, many of the actual earthquake-induced landslides have seriously affected mining operations in one way or another. Hence, this paper will treat earthquake-induced landslide phenomena in general, in the hope and expectation that the reader can apply this general knowledge to the specific problems associated with open pit mining. Ultimately, of course, the aim is to predict the likelihood of the occurrence of earthquake-induced landslides, and to delineate steps which can be taken to minimize the possibility of their occurrence. These aims can be achieved only imperfectly at the present time, for our knowledge concerning earthquake-induced landslides is still in an embryonic stage. Nonetheless, much useful knowledge does exist. In order to understand and apply this knowledge, it is necessary to: 1. Review the nature and extent of actual earthquake-induced landslides; 2. Have a grasp of the basic terminology and concepts of seismology; 3. Study the fundamentals of probability-based seismic risk analysis; 4. Appreciate the way in which earth materials behave during earthquake loadings; and 5. Have a general knowledge of the methods currently available for analyzing the dynamic response of slopes. Much of this paper is devoted to this necessary background. Information of practical use in connection with various classes of slope stability problems is assembled in the final sections. LANDSLIDES DURING PAST EARTHQUAKES Almost every earthquake in mountainous country, strong enough to be reported in the literature, has caused at least some landslides and rockfalls. Unless these slides or falls damage

Jan 1, 1971