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By C. Richard Tinsley

INTRODUCTION The economic analysis (Chapter 3), the engineering studies (Chapter 10), the credit structure (and the consequential funding sources) - Chapter 11, and the overall feasibility structure for any venture are all directed to determining one major decision element: How much and how certain is the reward for taking these risks? Risk assessment is a surprisingly weak area of analysis and is usually addressed in a checklist fashion. It is much preferable to deal within a risk system so that the inevitable tradeoffs among risks are correctly made. DEFINITION The first step toward risk definition must be to ascertain all of the risks to which a project or a company is exposed; otherwise one will remain ignorant of the possibility of a financially crippling loss until it occurs. (Carter and Crockford, 1974). However, simply stating what "risk" is can lead to debate. For example, risk could be (adapted from Vaughan, 1982): -the chance of a loss - uncertainty of loss -possibility of loss - uncertainty -dispersion of actual from expected results - probability of an outcome different from the one expected - possibility of an occurrence of an undesirable contingency -a condition in which a possibility of a loss exists. For the minerals industry financier, the last definition is probably the most appropriate. However, from a mineral company's point of view the definition might well include the possibility of not achieving the expected financial return. RISK CLASSIFICATION Risk identification will be readily agreed as the all-important first step. There are five major "branches" of risk classification. These are: -Statistical -Modellers -Checklist -Project Financing -Insurance The Statistical set discovered probability theory and any risk discussion soon deteriorates into a mathematical jungle (Megill, 1977; Hartman, 1976; Reutlinger, 1970; and Pouliquen, 1970).Their use of terminology tells its own story: coin toss (binomial distribution), gamblers' ruin, delphi (oracle) techniques, monte-carlo simulations, random walks, etcetera. These techniques inadequately represent the judgements necessary in an increasingly complicated and interrelated world. The risk Modellers have turned to the computer to handle these inter-relationships but soon find barriers because of "simultaneity". Certainly the computer has its uses to conduct various analyses (marketed as "sensitivity" analyses) but very often one finds that this involves changing one or two variables at a time, all other things being equal. Unfortunately, in a modern and complex world all other things do not remain equal. The statisticians will, no doubt, jump to their own defence by citing this

Jan 1, 1985

By Robert Leach

THIS paper gives a brief summary of the process of manufacture of sterling silver, and some of its more important physical properties, as observed in commercial production of rolled sheet and wire. Although papers have been published by Turner and Smith,1 Rose,2 Sperry3 and Jordan,4 there are few technical data available, and unfortunately the time allowed for the preparation of this paper has not been sufficient to make it as comprehensive as the title might indicate. ANALYSIS OF STERLING SILVER Fine or pure silver is too soft for coinage and the manufacture of articles in which strength and resistance to wear are desired. From the earliest times of which we have record, copper has been the metal generally used to harden silver. Analyses of coins and silver articles from ancient tombs show varying amounts of copper, and old Roman silver objects in the British Museum have approximately the same analysis as our sterling. The first authentic record of the establishment of a standard alloy is during the reign of Henry II in England. During the twelfth and thirteenth centuries, the people in the Eastern Provinces of Germany had a reputation for the standard and purity of their silver coinage, and it is said that Henry II employed some of these Easterlings, as they were called, to improve and standardize the English coinage, which had become debased. The peculiar standard adopted is probably accounted for by the system of weights used. A troy pound contains

Jan 1, 1928

With the advent of the environmental "green" movement of the 1960s, eventually leading to Earth Day 1970, Congress responded by passage of the National Environmental Policy Act (NEPA), 1970. NEPA gave impetus to a flood of federal acts and laws in the subsequent three decades. Many of those protecting man's environment, health, and well-being also affect mining. For purposes of this chapter, a current mineral law summarization lends itself to a division into two parts: viz., Part I, General Mining Law, and Part II, Enviromining Law. The word enviromining has been coined by the author and is defined and used herein as those federal and state statutes and regulations that were created to provide protection and preservation of man's environment, health, safety, and welfare, and they have particular application to and affect on mining activities. They are listed and treated under Enviromining Laws in Part II. Mining, as a basic industry to provide the essential minerals for mankind's necessities and well-being, truly reflects the mining industry's slogan, "If it can't be grown, it must be mined." Without the basic minerals and rocks won from the earth by mining and mineral processing for their valuable physical properties or chemical constituents, man would soon be forced to revert to the cave-dwelling age. Unfortunately, for man to survive in the "manner of life to which he has become accustomed," he is caught between the demands of cleaning up his deteriorating environment and a continued supply of his basic requirements and amenities for daily living supplied by mining of the earth's minerals. He must have "clean living" at the same time with "good living;" neither is expendable. A very high pricetag accompanies this essential and critical choice which must be paid by society. The United States is internationally recognized as the world leader in environmental matters. Many countries are following suit, principally the other Anglo nations. Because US law is founded and based on English law, on occasion, Anglo-American law is referred to and cited as authority in litigation anywhere in the Anglo-American world of jurisprudence. For this reason, and because mining and the industry is international in nature and operations, some British Commonwealth cases will appear in various topics. If the case is of interest to the reader, further inquiry at a law library may be made through use of the case's style and citation given. "Style" refers to the name of the litigating parties. "Citation" refers to the law publication in which the case and decision may be found, as well as the jurisdiction and court of decision. Citation of cases from the United States and British Commonwealth nations is explained under Case Citation Explanation. Space and time limit exhaustive treatment of subjects and covering all geographic and jurisdictional areas. This chapter is intended as a broad outline and is based on the author's master's thesis at the University of Missouri-Rolla, 1992. The following Case Citation Explanation provides guidance on formatting of citations.

Jan 1, 1994

THOSE who dabble in mining are no exception to the general rule that persons who know a little of a subject are apt to think that they know all about it. Some colour may be lent to the belief that anyone may succeed in mining when we hear stories ofsuccessful diggers and others who have accidentally dropped on to something good through no foresight on their part; but we seldom hear the contra account of the far larger number who fail. Those who go more thoroughly into the subject, and take up mining as a profession, know very well that it is not one that can be carried out successfully by rule of thumb, but when they point this out to the public they are credited with trying to make it a closed profession; and outsiders are for ever trying to find out the "trade secrets," at the same time spurning the main one, which is hard study, experience, and the ability to apply their knowledge. The average mining man is not rich. When he amasses a fortune it is generally through speculation rather than professional work, thought no doubt his technical knowledge may have assisted...

Jan 1, 1910

By B. Elevli

This paper deals with the selection of alternative accesses to a podiform chromite orebody in Turkey. The most important alternatives studied in a related project have been stated as a new vertical shaft and a ramp system. The comparison of these alternatives have been carried out on the basis of total investment costs, ore transport unit cost and net present value (NPV) of overall project for various depth. The results show that up to the depth of 700 m, the total investment cost and NPV favours the ramp access while unit ore transport cost make the shaft access preferable.

Jan 1, 2002

By Herbert Clark Hoover, Lou Henry Hoover

SINCE the Sixth Book has described the iron tools, the vessels and the machines used in mink, this Book will describe the methods of assaying1 ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure. Although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject. By tests of this kind miners can determine with certainty whether ores contain any metal in them or not ; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little ; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it ; and further, by these tests, they determine that part in which there is much metal from that part in which there is little. Unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. In the last case, they pass off with the fumes ; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things. Metals, when they have been melted out, are usually assayed in order that we may ascertain what pro- portion of silver is in a centumpondium of copper or lead, or what quantity of gold is in one libra of silver ; and, on the other hand, what proportion of copper or lead is contained in a centumpondium of silver, or what quantity of silver is contained in one libra of gold. And from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not. Further, a test of this kind shows whether coins are good or are debased ; and readily detects silver, if the coiners have mixed more than is lawful with the gold ; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. I will explain all these methods with the utmost care that I can.

Jan 1, 1950

By Alberto Barreda

A medida que la extracción del mineral progresa, la necesidad de madera en la construcción de edificios e instalaciones de la mina, también se incrementa. Por ello, el objetivo del presente trabajo señala la importancia de la madera como factor de producción en la industría minera, al tiempo que describe la silvicultura como técnica agronómica de ayuda en dicha manufactura. Revisando los cuadros estadísticos realizados en el Perú durante los años 1949- 1955, muestran que de cada extracción global de minerales (metálicos y carbón), obtenemos el promedio de 0,9 pies cúbicos de madera por tonelada de mineral extraído, con un equivalente de 5 pies tablares por pie cúbico, como factor de conversión. El problema surge cuando al intentar desplazar la venta de madera importada, se agotan las fuentes de desabastecimiento local, generando una crisis de reservas en el mercado libre. En consecuencia, se propone el establecimiento de plantaciones forestales en áreas localizadas y dentro del plazo de 10 a 12 años, las cuales prolongarán la conservación de la madera nacional, mejorarán la calidad de la misma y a su vez disminuirán los precios de venta.

Jul 20, 1956

Application of microprocessors, programmable logic devices, and other computer-oriented hardware and software on-board large surface mining equipment to optimize availability and productivity, stretch machine life, and protect against catastrophic breakdown has been a goal of heavy-equipment manufacturers for several years. Progress in this direction has not been as rapid as many manufacturers anticipated in the mid-1980s, and, on the other side of the coin, mining industry and machine operator acceptance of such products has not always been enthusiastic. However, the trend toward such development seems undeniable. Large surface mining equipment in the future will doubtless carry more, and not fewer, applications of computers and computer-related products. The intensity of development interest and degree of progress in commercializing such on-board computer and computer-related products on surface mining equipment varies considerably among the manufacturers. Summarized here are the on-board computer-oriented products of three heavy-equipment suppliers-P&H Harnishfeger, Marathon LeTourneau, and Haulpak not a comprehensive survey, but, perhaps indicative of the direction such development is taking.

Jan 1, 1990

By H. C. Meister

THE zinc-smelting industry of the United States has grown very rapidly in recent years and bids fair to outrival that of all other countries in the future. On account of the geographical situation of the chief ore-supplies, the industry may be divided into two main groups, the eastern and the western. The eastern and older group includes the works of Pennsylvania, New Jersey and Virginia, which practically control their own ore-supply. The western group includes the works of Illinois, Missouri, Kansas, Wisconsin and Indiana, which do not control their own ore-supply, but are compelled to buy the ore in the open market. It is for this reason that the western zinc-smelting industry has been undergoing continual changes since its inception 40 years ago. During the early discoveries of lead- and zinc-ore in the lead- and zinc-districts of Wisconsin and northern Illinois, the zinc-ore (sinithsonite or " bone " as the miner calls it) had no value and was considered waste; but later, when this ore was found in large quantities, it attracted the attention of metallurgists, which finally resulted, during the early sixties, in the building of the Matthiessen & Hegeler Zinc Works at LaSalle, Ill., the pioneer zinc-works of the West. A few years later, zinc-ore was discovered associated with the lead-ore in Jefferson county, southeastern Missouri, which started the industry at Carondelet or South St. Louis. Still later, the discoveries of zinc-ore in the lead-ore region, first' at Granby and then around Joplin, lead to the introduction of the industry in the southwest Missouri and Kansas districts. At first the development of the industry was slow, but it progressed steadily and it is now one of the leading metallurgical industries of the middle West.

Jan 1, 1905

By A. Choudhury

Deep open-pit mines are becoming increasingly common in the highly mineralized arctic and sub-arctic regions. Air inversion is a frequent occurrence in these regions, and is exacerbated by the natural topography of an open-pit mine. Due to such inversions, the air quality in open-pit mines deteriorates very rapidly. Transport of gaseous pollutants under arctic air inversion is complex and involves an interaction between flow, thermal and convective transport systems. This paper discusses the construction and validation of a three-dimensional model that simulate the flow of air and the transport of gaseous contaminants in an arctic open-pit mine and the effect of low influent velocity and large gust velocities on the contaminants profiles in the mine. It was found that while higher velocities may remove contaminants from the pit bottom, they may not remove the contaminants from the pit entirely, necessitating artificial mitigation measures.

Jan 1, 2012

By I. R. Kramer

I. R. Kramer (Martin Co.)—In a recent paper Nakada and Chalmers24 reported some observations of effects of surface conditions on the stress-strain curves of aluminum and gold single crystals. It is of interest to compare these observations with the results published previously in this journal and to comment on their general conclusions. In brief, Nakada and Chalmers concluded that the removal of the surface layer of a prestrained specimen lowered the stress-strain curve for aluminum but not that for gold. Further, they concluded that the surface work hardening of aluminum is confined to a depth not more than l0-3 cm. In our results25 published previously, it was pointed out that when prestrained specimens of aluminum and gold were polished to reduce the thickness upon reloading the initial flow stress decreased markedly. Further if a sufficient amount of metal was removed, the yield point failed to appear. With continued application of the load the stress-strain curve became coincident with that of the virgin crystal. We have found this behavior in some 100 determinations to hold consistently for gold, aluminum, and copper in both single and poly-crystalline specimens. The amount of strain required before the curves coincided depends upon the amount of metal removed but it is usually less than 0.01. This type of behavior is the same as that reported for metarecovery by other investigators.29 For aluminum specimens which have been prestrained and then heated to temperatures above 50°C we have consistently found that the stress-strain curve was typical of the orthorecovery28 type. In this case the stress-strain curve always lies below that of the virgin specimen. With respect to Ref. 24 the curves for aluminum are always below that of the virgin curves, while those for gold become coincident. This observation indicates at least for aluminum that the specimens must have been heated to a temperature high enough to cause recovery by an alteration of the internal dislocations. In addition, a recovery would be expected because of the removal of the surface work-hardened layer. Nakada27 had reported that, with his particular apparatus in which a perchloric acid polishing solution was used, the temperature of the specimen increased 65°C. The curves presented in Ref. 24 for gold do not permit one to detect the initial flow stress upon reloading after the surface-removal treatment. In fact, contrary to the method used by Nakada and Chalmers, the change in the stress-strain curve produced by a surface-removal treatment cannot be described in terms of a decrease in stress at strains much higher than that at the initial flow stress because of the coincidence of the curves at the higher strain values. With regard to the depth of the work-hardened surface layer, our data show for aluminum single crystals (7.5 by 0.3 by 0.3 cm) that the initial flow stress remained constant after 12 x 10-3 cm had been removed from the thickness. This depth was independent of the prior strain. For gold crystals this depth is somewhere between 10 x 10-3 and 20 x 10-3 cm. Y. Nakada (author's reply)— Kramer states,28 "for aluminum specimens which have been prestrained and then heated to temperatures above 50°C, we have consistently found that the stress-strain curve was typical of the orthorecovery28 type. In this case the stress-strain curve always lies below that of the virgin specimen." However, Cherian et a1.26 discovered that aluminum polycrystals annealed at 32" and 100°C showed the metarecovery behavior. They showed that the orthorecovery behavior did not appear until the crystals were annealed at 150°C. Kramer suggests28 that the drop in the flow stress of aluminum crystals after the surface removal by electropolishing24 may be due to the recovery caused by the temperature rise which may occur during the electropolishing.27 However, as indirectly stated in Ref. 24, the current density used in these electro -polishing experiments was 0.15 amp per sq cm. According to ref. 27, this current density should cause a temperature rise of only 40°C. This may cause the metarecovery but not the orthorecovery. Furthermore, as stated explicitly in Ref. 24, the surface removal was accomplished by chemical etching as well as by electropolishing. The results were the same for both electropolishing and etching. During the etching, the specimen temperature did not rise above 35°C. Some aluminum crystals were placed in water at 35° C for 30 min. These crystals did not show the decrease in flow stress. Therefore, it is quite clear that the flow-stress drop after the surface removal is not caused by a high-temperature recovery. However, as Kramer points out,28 it is quite possible that the internal dislocation structure may have been altered because of the removal of the highly work-hardened surface layer. However, how much this rearrangement contributes toward the flow-stress decrease is not known at present.

Jan 1, 1965

By Charles Hardy

?POWDER METALLURGY? is the production of semiformed or fully formed metal products by compressing metal powders. It had its beginnings in the fabrication of tungsten and molybdenum bars and wire by compression, sintering, and swaging. Powder metallurgy, although still in its infancy with other metals, has shown remarkable progress in recent years. Production of Metal Powders-The first step in any powder-metallurgy process is the production of metal particles of suitable shape and size. Mechanical processes for producing metal powders, as by crushing, stamping, or grinding, are usually not suitable, as the resulting particles may cause laminations and decreased strength in the finished articles. The principal metal powders now in use on a large scale are produced by electrolysis or by reduction of metal oxides by gases.

Jan 1, 1936

By R. E. Murray

"It is a gloomy moment in the history of our country. Not in the lifetime of most men has there been so much grave and deep apprehension; never has the future seemed so incalculable as at this time. The domestic economic situation is in chaos. Our dollar is weak throughout the world. Prices are so high as to be utterly impossible. The political cauldron seethes and bubbles with uncertainty. Russia hangs, as usual, like a cloud, dark and silent, upon the horizon. It is a solemn moment. Of our troubles, no man can see the end." By now you, no doubt, are asking, 'Where did Murray get this bit of philosophy?' Well, I obtained it from an editorial entitled. "The Worst of Times", which was published in the Harper's Magazine in 1847. That's right, 1847! The parallelism between the situation in our country at this time and in 1847 is un- canny. But wait, there is one major exception the size of government. To my knowledge, the citizens of 1847 were not stifled by the extreme governmental excesses that we are experiencing today.

Jan 1, 1980

By K. Takahashi

Generally speaking, wastewater coming from the metallurgical process for recovering precious metal contains precious metals such as gold (Au), platinum (Pt), palladium (Pd), Silver (Ag), etc., which concentration is about 10 mg/L. In addition, there are other metals such as copper (Cu), iron (Fe), which concentration varies from several mg/L to more than 10,000 mg/L. It should be noted that the concentration of metals in wastewater is relatively high, considering the fact that these metals of similar concentration can be found in ores. However, most of these valuable metals are not treated, due to the high processing cost and technical problems. Within this frame, the authors put forward a new process that includes neutralization/reduction, precipitation and fusion. The idea is to recover and recycle Au, Ag, and Pd metals as well as protecting the environment by saving the resources. It was found that this new process was able to recover more than 90% of Au, Ag and Pd.

Jan 1, 2014

By F M. Weir, M Fowler

A discrete fracture network (DFN) approach involves numerical modelling that explicitly represents how defects may be spatially distributed through a rock mass. A DFN is a 3D realisation of the ‘smaller scale’, non-deterministic defects; it is not an attempt to model larger, deterministic structures that should be identified as part of an engineering geology model. The approach utilises structural data in stochastic analyses to give a range of possible models that provides a tool for visualisation and analysis of a rock mass and indicates the potential large-scale slope or tunnel performance and stability.Stochastic fracture modelling for rock mass characterisation has significantly advanced over the past 25 years. With recent improvements to field data collection and computational power, it has become recognised internationally as a valuable tool for modelling some geomechanical problems encountered when designing excavations in fractured rock masses.This paper provides an introduction to the DFN approach, particularly the necessary input parameters and derivation of these from typical structural data sources, such as boreholes or scan line mapping. Of particular importance for engineering applications is validation of the simulated fracture network and techniques for doing so are discussed here.CITATION:Weir, F M and Fowler, M, 2014. An introduction to discrete fracture network modelling and its geotechnical applications, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 435–444 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By Julie Dénommé

Today few in business would argue with the idea that we are living in a world that is Volatile, Uncertain, Complex, and Ambiguous. Coined VUCA by the US Army War College, these four words define the ?turbulence? and ?continuous white water? that the business literature has been documenting for the last decade. This VUCA world became even more relevant to business in 2007 when the Institute for the Future fellow Bob Johansen published the idea of transforming VUCA into Vision, Understanding, Clarity, and Agility. We call this VUCA Prime (VUCA'), and place an infinity loop (8) between them to show their dynamic interaction. This paper presents an exploration of the impact of VUCA 8 VUCA' on business and the conditions under which these dynamic forces help to successfully navigate change.

Oct 1, 2010

By H. F. Moore

DURING the last six years, there have been many extensive investigations of the fatigue of metals. The major work of 'these investigations has been the determination of constants for fatigue strength of wrought ferrous metals; but during the past year or two there have become available considerable test data on the fatigue strength of certain nonrferrous metals, including copper, brass, bronze, nickel, copper-nickel alloys, aluminum and aluminum alloys, magnesium and magnesium alloys. It is not proposed to give here extensive quantitative tables of test results; for such tables, reference is made to the published data of various laboratories. The following general conclusions, however, seem to be fairly well established: 1. The phenomenon known as "fatigue" of metal really a progressive fracture of metals. A minute (probably submicroscopic) crack is formed in the metal, the internat stress, is intensified at the ends' of the crack, and under successive applications of load the crack spreads like a minute hacksaw cut until there is not enough sound metal left in the cross-section of the piece to stand the load. applied, and then failure occurs suddenly. 2. For wrought ferrous metals, there is .a limiting intensity of stress (as computed by the ordinary formulas of mechanics of materials) below which, a metal is able to withstand an indefinitely large number of repetitions of stress without failure. This limiting stress is known as the "endurance limit or the fatigue limit.? For reversed flexure, the endurance limit for. wrought ferrous metals is usually not far from 50 per cent. of the ultimate tensile strength.

Jan 1, 1925

By M. G. Fleming

The professional mineral engineer is an individual of personal integrity who has undergone rigorous intellectual instruction in the scientific disciplines fundamental to his vocation; he has learnt to apply these disciplines to the discovery, mining and treatment of mineral resources and, through practical training and experience, has acquired competence and judgment to fulfil his undertakings. In the course of this development he has recognised and accepted a threefold responsibility to society, to his employer and to his profession

Dec 1, 1971

By Earl T. Hayes

THIS BIBLIOGRAPHY has been assembled to aid research by the Bureau of Mines, and others on high-purity tungsten. It appears approximately 50 years after the development of ductile tungsten-one of the first metals to be produced in a high-purity form. Requirements of the missile age are ever more demanding that engines rout hotter and space vehicles fly higher and faster. Thus, it has become necessary to reexamine all conventional materials of construction as well as to investigate new combinations. At this stage of our technology we have alloys capable of operation at 1,800° F. and several possibilities of developing some. that will be satisfactory up to 2,500° F. Strength-weight comparisons, detrimental to tungsten at, lower temperatures, disappear at this point, mid tungsten or its alloys appear to be the only metal capable of operation at truly high temperatures. The aim of this bibliography has been to include only references that concern improving the purity of tungsten-from processing the ore to treating the finished metal. In this sense it is a selected and not a critical bibliography. The period front January 1911 through February 1959 has been covered. Because repent literature has the greatest, value, most of the selected items refer to publications issued within the pest 5 years.

Jan 1, 1960

By J. J. Gilman

The dependence of ortho kink-band formation on crystal orientation, on temperature, and on the conditions at the ends of a specimen is described. Load-compression curves for crystals that kink are presented. The reversibility of ortho kinking is demonstrated, and motion of kink planes through crystals is shown. Finally, a phenomenological explanation of ortho kink-band formation is given. ORTHO compressive kink bands (Fig. la) were discovered for the case of metals by Orowan,1 and they have been discussed by Jillson2 and in some detail by Hess and Barrett." However, their history in nonmetallic crystals is considerably older. It is not known when they were first observed in mineral crystals, but descriptions of them may be found as early as 1885.* They were sometimes mistaken for twins.6 Mügge seems to have been first to realize their true nature and importance. He reviewed the knowledge of them for a wide variety of crystals: anhydrite, antimonite, kyanite, vivianite, gypsum, mica, graphite, molybdenite, barium bromide, cal-cite, sodium nitrate, and barite. Also, the "twins" observed by Bridgman7 in sapphire crystals resemble kink bands more than twins. The terms ortho and para kink bands have been coined in order to distinguish between two types of kink bands which seem to represent the same geometrical configurations, but which have different origins and sizes. Ortho kink bands are the usual type that form at low loads when zinc crystals are compressed parallel to the basal plane. Para kink bands form at much higher loads in highly deformed crystals. These terms refer to compression phenomena and are not to be confused with analogous tension phenomena such as tensile kink bands and deformation bands. Mügge described the geometry of ortho kink bands quite completely for kyanite crystals, Fig. lc. The geometry observed for cadmium by Orowan1 and for zinc by Hess and Barrett3 is very similar to that described by Mügge. (See Hess and Barrett for a complete discussion.) Mügge associated kinking with bending combined with basal slip. He pointed out that the kink angles

Jan 1, 1955