Search Documents

By Nicholas T. Camicia

A career in the coal mining industry today offers students one of the most interesting and challenging opportunities available in the industrialized world. As reserves of other fossil fuels dwindle in face of the world's demand for energy, it has become apparent that coal, once the king of energy sources, must be relied upon again as the major fuel for powering industrial growth in developed and developing nations. Centuries of coal supplies lie beneath the earth's surface, assuring the world of a steady, plentiful supply of energy until science and technology can produce a way to harness and efficiently use renewable sources, such as solar. The need to increase our use of coal during the last two decades of the 20th century is reason enough to believe that the future growth of the coal industry is assured. A major impediment to that growth might be backward national public policies that could restrict the full utilization of our coal reserves. These policies could result from overregulation and a failure of the public to recognize that coal use, with proper techno- logical safeguards, is compatible with our society's environmental-quality objectives. Communication of this problem and its solution is a major undertaking of the coal industry in the 1980s. At the end of the 1970s7 the American coal industry was producing approximately 635 Mt/a (700 million stpy) of coal. To meet the nation's projected energy needs by 1985, the annual tonnage must be doubled. A similar scenario is predicted for the rest of the world. Such growth in the modern international business world will require huge additional amounts of capital, equipment, and people who know how to wisely raise and apply the capital; use the equipment productively; and deal with the many community, public, and governmental problems such expansion will create. Whether a student's interest is in actual mining operations, business administration, engineering, finance, law, industrial relations, marketing

Jan 1, 1981

By Nicholas T. Camicia

A career in the coal mining industry today offers students one of the most interesting and challenging opportunities available in the industrialized world. As reserves of other fossil fuels dwindle in face of the world's demand for energy, it has become apparent that coal, once the king of energy sources, must be relied upon again as the major fuel for powering industrial growth in developed and developing nations. Centuries of coal supplies lie beneath the earth's surface, assuring the world of a steady, plentiful supply of energy until science and technology can produce a way to harness and efficiently use renewable sources, such as solar. The need to increase our use of coal during the last two decades of the 20th century is reason enough to believe that the future growth of the coal industry is assured. A major impediment to that growth might be backward national public policies that could restrict the full utilization of our coal reserves. These policies could result from overregulation and a failure of the public to recognize that coal use, with proper techno- logical safeguards, is compatible with our society's environmental-quality objectives. Communication of this problem and its solution is a major undertaking of the coal industry in the 1980s. At the end of the 1970s, the American coal industry was producing approximately 635 Mt/a (700 million stpy) of coal. To meet the nation's projected energy needs by 1985, the annual tonnage must be doubled. A similar scenario is predicted for the rest of the world. Such growth in the modern international business world will require huge additional amounts of capital, equipment, and people who know how to wisely raise and apply the capital ; use the equipment productively; and deal with the many community, public, and governmental problems such expansion will create. Whether a student's interest is in actual mining operations, business administration, engineering, finance, law, industrial relations, marketing and sales, or public affairs, a career opportunity is available in the industry.

Jan 1, 1981

By Nicholas T. Camicia

A career in the coal mining industry today offers students one of the most interesting and challenging opportunities available in the industrialized world. As reserves of other fossil fuels dwindle in face of the world's demand for energy, it has become apparent that coal, once the king of energy sources, must be relied upon again as the major fuel for powering industrial growth in developed and developing nations. Centuries of coal supplies lie beneath the earth's surface, assuring the world of a steady, plentiful supply of energy until science and technology can produce a way to harness and efficiently use renewable sources, such as solar. The need to increase our use of coal during the last two decades of the 20th century is reason enough to believe that the future growth of the coal industry is assured. A major impediment to that growth might be backward national public policies that could restrict the full utilization of our coal reserves. These policies could result from overregulation and a failure of the public to recognize that coal use, with proper techno- logical safeguards, is compatible with our society's environmental-quality objectives. Communication of this problem and its solution is a major undertaking of the coal industry in the 1980s. At the end of the 1970s, the American coal industry was producing approximately 635 Mt/a (700 million stpy) of coal. To meet the nation's projected energy needs by 1985, the annual tonnage must be doubled. A similar scenario is predicted for the rest of the world. Such growth in the modern international business world will require huge additional amounts of capital, equipment, and people who know how to wisely raise and apply the capital; use the equipment productively; and deal with the many community, public, and governmental problems such expansion will create. Whether a student's interest is in actual mining operations, business administration, engineering, finance, law, industrial relations, marketing

Jan 1, 1981

By E. A. Metz

Work related pulmonary diseases are in the top TEN causes of occupational disability and death in the United States. Likewise, it also ranks high inmost of the other industrial countries. It is difficult to know the true occurrence of occupational lung disease because of poor documentation. This is especially true when one examines workers’ compensation claims. Most frequently, silica and asbestos are paramount in our discussion of work related pulmonary disease. Little consideration is given to other “dust-related” diseases, irritant reactions, reactive airway responses, and hypersensitivity reactions. The major classification of occupational lung diseases will be discussed. This includes both acute and chronic disease that arises in the work place, especially, the mining industry. It’s more important to make an accurate evaluation and diagnosis for the prevention of disease among other workers.

Jan 1, 2000

By C. E. Roessler

Uranium and its decay series are associated with phosphate deposits of marine origin. Uranium concentrations are on the order of 100 to 200 ppm in matrix from the Bone Valley formation of Central Florida and about 25% this value in matrix mined from the Hawthorne formation in North Florida. Occupational radiation exposure due to this source has been under study in Florida since the mid 1970's (Windham, Partridge, Horton 1976; Roessler and Prince 1978). This report is based on findings of an industry-wide scoping survey conducted by the University of Florida during March 1976 through May 1977 and subsequent studies in selected individual facilities. PHOSPHATE MINING OPERATIONS Mining and beneficiation operations are diagramed in Figure 1. At the excavation site, electric powered draglines remove the overburden and expose the phosphate matrix (ore) which is then slurried and pumped to the beneficiation site. At the washer stage of the beneficiation plant, the matrix is subjected to washing and screening. A coarse product, "pebble" is produced and sent to storage piles while the fine fraction is passed through a series of cyclones to remove the clays. The generated clay suspension is sent to settling ponds while the remaining sand-sized fraction is sent to the flotation plant. At the flotation plant, phosphate particles are recovered from the fine sand particles of similar size through several stages of treatment with reagents, agitation and separation of floating and sinking fractions. The high grade concentrate produced is transferred to storage while the sand tailings are discarded. [ ]

Jan 1, 1981

By P. Pages, J. Lombard, F. Fagnant, G. Bresson

This study is devoted to the improvement of the decision-making process in occupational protection of uranium miners in France. Its purpose is to apply the principles which are recommended by the I.C.R.P. in the field of radiation hazards. These principles, which have introduced the notion of "optimization" in standard setting, suggest the importance of applying cost-benefit and cost-effectiveness analysis to this sector. The objectives here are twofold : to evaluate the present organization of radiation protection on the basis of a simulation model of polluted air flow in the mine (due to the decay of a radioactive gas, radon) and to develop cost-effectiveness analysis of the various radiation protection policies.

Jan 1, 1981

By J G Bastias

It is sometimes necessary to resort to extremes in order to call attention to something that is pertinent to safety in mining. When some of the experts in occupational safety talk about this topic, they usually refer to a 'regulation' established by the Romans which stated that, due to the health hazards, usually death, no Romans but only slaves should work in mining. Since the time of the Roman Empire, a lot of ground has been covered in the field of mine safety. Nowadays, it can be said that occupational safety is being seriously addressed, with the result that the number of mining accidents has reduced dramatically, fatalities in this industry are less frequent, and the rate of accidents compared with other activities, such as construction or fanning, is low. This achievement has been possible initially through government legislation and by procedures established by the mining companies themselves. However, the dilemma for government is whether to regulate and if so, how much. It is pleasing to observe that most companies are establishing working procedures which conform with new government legislation, placing strong emphasis on the duty of care for mine employees. There will always be some regulatory aspects of legislation, and perhaps the best example of this is in the use of mine hoists where there are no international or Australian standards, and the regulations applied are of an empirical nature that err on the side of safety.

Jan 1, 1994

No Paper

Jan 1, 1996

By Mary Ann Bennett, Val Nichols, Colleen Proctor

"In 1997 when Royal Oak Mines Inc. went into receivership, the mineral processing technicians (mill operators) who had been working at Giant Mine in Yellowknife, Northwest Territories for most of their career walked out with no credentials to serve as testimony of their knowledge and skills.As a result of new diamond mining activity and the establishment of socio-economic agreements, mining industry representatives approached the Department of Education, Culture and Employment (ECE), Government of the Northwest Territories, in 1999. They requested support and direction to promote training and recognition for mineral processing technicians at BHP’s (BHP Diamonds Inc.) Ekati mine. ECE recommended the development of occupational standards and certification.This paper describes the development process and end products that resulted from this collaborative project between industry, government and education. In addition, industry representatives involved in the project share their views on the development process and the benefits of standards and certification.The conclusion invites industry members to support national occupational standards and certification with their associated benefits: standardized training in the workplace and institutions, proof of competence for hiring, recognition of prior learning, and a nationally and internationally recognized credential.INTRODUCTIONSwiftly changing labour market demands are nothing new in the North. The fur trade and mineral discoveries have brought employment to workers in a feast and famine cycle for decades. In the late 1990s, the Giant, Con, Lupin, Polaris and Nanasivik mines were nearing the end of productive runs. Many experienced workers found that without credentials, they had no proof of their abilities to offer prospective employers."

Jan 1, 2005

By T. R. Eger

Miners can be exposed to whole-body vibration (WBV), when sitting or standing to operate mobile equipment. In order to prevent vibration-induced injury it is important to understand how miners can be exposed to vibration, the health risks associated with vibration exposure, methods to evaluate vibration exposure, and strategies to reduce vibration exposure. WBV exposure typically occurs when operating mobile equipment, such as a load-haul-dump vehicle, haulage truck, or dozer. The probability of health effects such as low back pain, neck pain, headaches, and gastrointestinal track problems occurring from daily vibration exposure can be determined based on criterion values published in ISO 2631-1 and EU Directive 2002/44/EC. A special case of WBV termed foot-transmitted vibration (FTV) occurs when a miner is exposed to vibration that travels through the feet. FTV typically occurs when standing on vibrating surfaces associated with the operation of locomotives, jumbo drills, bolters, or raise platforms; however, there is no set standard to evaluate health effects associated with FTV. Recent medical evidence confirms workers exposed to FTV can develop cold induced blanching of the toes, in addition to numbness and tingling in the feet and toes. In order to reduce the risk of adverse health effects from exposure to vibration, the hierarchy of controls (elimination; substitution; engineering; administration; and personal protective equipment) should be followed. Best practices should be used to minimize vibration exposure through equipment purchases (i.e. vehicles with lower vibration emissions and seats that attenuate vibration), reduced driving speeds, and improved road maintenance for example. The elimination of other risk factors, which increase injury risk when combined with WBV exposure, such as awkward working postures, should also be eliminated. Very little is known about FTV exposure therefore further research is required in order to develop exposure standards and identify prevention strategies.

Aug 1, 2013

By Patrick Browne

Drilling programs and the study of active geothermal systems have shown that the reservoir rocks in many fields contain minor quantities of base and precious metals. Commonly, base-metal sulfides occur in the subsurface but, where present, Au, Ag, Hg, As, T1 and Sb rich precipitates deposit near, or at, the surface. Although in some fields (Geysers, Larderello, Tongonan) some of the ore minerals (and others) are relict, there is evidence that they are now depositing in a few systems. Recent work on active hydrothermal systems in New Zealand shows that: (1) Sphalerite, galena, chalcopyrite (forming veins and disseminated discrete crystals) plus rare pentlandite, cobaltite and arsenopyrite, occur at Broadlands, NZ. Rare quantities of base-metal sulfides also occur in cores and cuttings from the geothermal fields of Waiotapu, Kawerau, Tauhara, and Ngawha. Further, Kakimoto (1983) has identified cassiterite, native silver, and trace gold in cores from Tauhara, in the south-eastern part of the Wairakei field. Bore temperatures at the depths from which these minerals were recovered are mostly between 220° and 300°C, but at Broadlands are locally as low as 120°C. The host rocks are Quaternary talc-alkali, silicic lavas and pyroclastic rocks, andesites, dacite and deep Mesozoic greywackes and argillites; however, there is no obvious relationship between mineralization and stratigraphy, permeability or well output. (2) The deposition of amorphous precious metal precipitates (Au, Ag, Hg, As, Sb, T1) from hot springs and well discharges has taken place at Broadlands, Waiotapu and Rotokawa; it also occurs at Kawerau. (3) Water discharging from Frying Pan Lake, Waimangu, is presently depositing siliceous sinter containing up to 4.1% tungsten. A characteristic of mineral-depositing fluids in the New Zealand geothermal fields is their very low salinity (total dissolved salts of 3000 ppm or less but with high CO2); they are of near- neutral alkali chloride composition, although water discharging from Frying Pan Lake has a pH of 4.5, and very low metal contents. Very effective concentration processes (10 times for gold at Broadlands) must occur: in the subsurface these include boiling and rapid cooling but near, and at, the surface, mixing of waters of different pH seems to dominate. In particular, descending acid condensate, derived from separated steam and oxidation of H2S mixes with its parent alkali chloride water, resulting in precipitation of amorphous ore metals. Base-metal sulfides also occur in veins and as disseminated grains in geothermal fields at Tongonan, Leyte and Southern Negros, Philippines. These fields have a porphyry-type setting with host rocks of Miocene andesitic lavas and pyroclastics intruded by diorites so that the fields have undergone complicated thermal histories before cooling to their present base temperatures of about 325°C. Precious metals have precipitated from waters from some wells (Leach, pers. comm.) but they do not, as yet, form ore-grade deposits.

Jan 1, 1984

By R. C. Corey

GERMANIUM is an element that has come into widespread use in the electronics industry in recent, years. So far this increasing demand has been, met by ample supply: however, the future balance is uncertain, and the need has been recognized to discover additional domestic sources of germanium. This investigation was conducted to study the possibility of obtaining a potential supply of germanium from coal or coal ash. It has been known for some time that coal contains germanium; the discovery that By ash from coal-fired boilers often contains appreciably more germanium than the original coal suggested the possibility that coal ash might be an abundant and economical source of this element. In this study the concentration of germanium was determined in numerous samples of coal and ash. A number of miscellaneous waste materials also were examined in the course of the investigation; the results are reported as a matter of general interest. The methods and equipment employed are discussed in detail. Sample-preparation and analytical techniques are described in the appendix. Spectrographic analyses were made on a total of 639 samples, including coal, coal ash, slap ash from lignite and peat, wood ash, and various inorganic materials. Qualitative analyses were run on all samples, and quantitative determinations were made on those samples that contained enough germanium to be measured by this method The lower limit at which germanium can be determined quantitatively by spectrographic analysis is 50 parts per million (p. p. m.), but concentrations of less than 20 p. p. m. can be detected qualitatively.

Jan 1, 1959

By S. Edward Drummond, Charles D. Haynes, Stephen H. Stow

This paper is a preliminary report on the occurrence and distribution of economically interesting heavy minerals (kyanite, sillimanite, staurolite, zircon, monazite, ilmenite, leucoxene, rutile) in sands from the sea floor surface of the offshore area, Alabama-Mississippi. Weight percent of heavies derived from the +60 portion of 97 samples is contoured in [Fig. 1]. Five hundred grains from 42 of the heavy mineral separates were identified and sized microscopically; the data were converted to weight percent for each mineral species and are summarized in [Table 1]. Heavy Mineral Distribution In the Gulf, there is a general westward decrease [(Fig. 1)] in maximum abundance of heavies from 2.4% north of Sand Island at the mouth of Mobile Bay to slightly over 1.0% south of Petit Bois Island and a corresponding decrease in the Mississippi Sound from 1.4%, north of Dauphin Island to slightly over 0.25% north of Horn Island. Average concentrations of heavies for different areas are found in Table 1. There is westerly longshore transport in this area; the interaction of the longshore current with discharge from Mobile Bay and disruptions of the current by Sand Island, possibly aided by a shoaling effect, appear to be the cause of the preferential deposition and concentration of heavies (2.4%) north of Sand Island in 10 to 14 ft of water.

Jan 1, 1977

By C. J. B. Dreyer, H. A. Robinson

Only South Africa can be considered in terms of resources of amphibole asbestos. There are two asbestos producing fields, one in the Northern Cape Province (producing only crocidolite), and one in the Eastern Transvaal (producing only amosite). This chapter discusses the banded ironstone sequence in which amphibole asbestos occurs, and the genesis of the fiber is briefly reviewed. Also, the properties and characteristics of amphibole asbestos are discussed and compared to those of chrysotile. Approximately 300 000 t of arnosite and crocidolite are produced annually. Crocidolite has a potential for a fivefold increase of production chat could be sustained beyond the year 2000. An estimate of the resources of the various producing fields in South Africa is made. The mining methods are also reviewed and evaluation techniques are discussed. The only two types of amphibole asbestos exploited at present in South Africa are amosite [the white colored amphibole asbestos) and crocidolite (the blue colored asbestos). As is well known, crocidolite has been mined in South Africa from the early part of this century, and amosite since the early 1930's. Since these dates, asbestos mining has developed into a significant mining industry. The annual production of crocidolite is approximately 170 000 to 200 000 t. and amosite production is in the region of 80 000 to 100 000 t. CLASSIFICATION OF AMPHIBOLE ASBESTOS Four types of amphibole asbestos are produced economically in the world today: (1) crocidolite, the fibrous equivalent of riebeckite, (2) arnosite, the fibrous equivalent of grunerite, (3) trernolite, and (4) anthophylite. The names trernolite and grunerite apply equally to the crystal and fibrous forms of these minerals. For comparison and clarification purposes, the six known varieties of asbestiform minerals known in the world are shown in Table 1. All the asbestos minerals were originally developed as cross fiber seams in veins or fractures, or were controlled by the lithology. Post- fiber effects caused slip, sheared, and folded fiber seams. Crocidolite and amosite occur in banded ironstone of early Proterozoic age of the Transvaal Supergroup. The fiber seams are developed in certain defined lithological units in the banded ironstone sequence. The lithological units have a remarkable lateral persistence with respect to their chemical nature and physical appearance. Vertically, the banded ironstone sequence displays a heterogeneous nature. Commercial Applications The features and properties that make amphibole asbestos commercially attractive are: 1) The long average length of the fibers is good for greater wet strength in composites. 2) The high tensile strength of crocidolite makes it superior to all other types of asbestos. 3) It is characterized by dispersion in most liquid media, particularly amosite in water. 4) Since the surface charge of amosite and crocidolite is negative, the fibers produce an open lattice work in water with a high bulk volume giving excellent filtration rates and rapid drainage in a wet asbestos cement mix. 5) The insulating properties of amphibole asbestos mats are still important, particularly in a corrosive environment, despite the introduction of many other synthetic insulating materials. 6) Corrosion resistance, particularly acid corrosion resistance. 7) Due to the high modulus of amphibole fibers, resins reinforced with these fibers exhibit

Jan 1, 1986

By Thomas L. Kesler

Essentially all of the barite produced in Georgia has come from the Cartersville district in the northwest part of the state. The earliest recorded shipment of ore, 60 tons, was made in 1894.1 With the exception of the four-year period 1931 to 1934, the separate yearly output has been recorded and published since 1915, whereas the total yearly output of the United States has been published since 1880. The separately recorded production of Georgia (Cartersville) through 1947 is 2,232,544 short tons valued at $14,900,746,2 but unpublished data on the period 1931 to 1934, plus the estimated unrecorded output prior to 1915, make the actual total about 2,400,000 short tons. This is about 21 pct of the total production of the United States, which, through 1947, is 11,328,440 short tons valued at $71,683,386.2

Jan 1, 1949

By Thomas L. Kesler

IF all of the 14 million tons of kaolin produced in Georgia through 1949 had been mined from a single deposit 20 ft thick, it would represent a mined-out area of less than 1 sq mile. This measure of depletion is in such strong contrast with the large size of the area shown in Fig. 1, from which most of the output has come, that there has developed an optimistic outlook concerning future supplies of kaolin equal in grade to that already mined. Dozens of mines are widely but not evenly distributed within this area, which consists mostly of parts of Twiggs, Wilkinson, and Washington counties. There are scarcely half a dozen kaolin mines elsewhere in the state that have been appreciably productive, although the areas in which they occur may have good possibilities. Most of the efforts to find new deposits, therefore, will be confined to the area shown in Fig. 1, for it is here that the industry has established its facilities, and prospecting is encouraged by relatively numerous outcrops and opened deposits of kaolin.

Jan 10, 1951

By Thomas L. Kesler

IF all of the 14 million tons of kaolin produced in Georgia through 1949 had been mined from a single deposit 20 ft thick, it would represent a mined-out area of less than 1 sq mile. This measure of depletion is in such strong contrast with the large size of the area shown in Fig 1, from which most of the output has come, that there has developed an optimistic outlook concerning future supplies of kaolin equal in grade to that already mined. Dozens of mines are widely but not evenly distributed within this area, which consists mostly of parts of Twiggs, Wilkinson, and Washington Counties. There are scarcely half a dozen kaolin mines elsewhere in the state that have been appreciably productive, although the areas in which they occur may have good possibilities. Most of the efforts to find new deposits, therefore, will be confined to the area shown in Fig 1, for it is here that the industry has established its facilities, and prospecting is encouraged by relatively numerous outcrops and opened deposits of kaolin. The Ounulgee and Oconee Rivers drain the area. They and their main tributaries have flat, swampy flood plains covered with alluvium and for the most part thickly wooded. The divides between these streams are intricately dissected by the minor tributaries, which are spring-fed in steep-walled, cirquelike heads. Gullying and undercutting are active along the streams but are partly controlled by unusually dense vegetation. The mean altitude is about 350 ft above sea level and locally the relief ranges up to 200 ft. The area is near the inner margin of the Coastal Plain, and is underlain by Cretaceous and Tertiary formations. Its general location is shown in black in Fig 1. The division between the Coastal Plain and the Piedmont Plateau is actually a very sinuous line, the fall line, marking the extent to which erosion has stripped the Coastal Plain sediments from the southeastward- sloping surface of the crystalline rocks of the Piedmont.

Jan 1, 1952

By M A. Wells

The various mechanisms by which phosphorus (P) occurs and is distributed within banded iron formations (BIF)-derived iron ore are examined. In unenriched, precursor BIF P occurs predominantly as discrete grains of primary apatite. In high-grade ores hosted mainly by the Brockman Iron Formation, P occurs in three main forms:1. as secondary apatite;2. other submicron, P-rich phases (eg Rare earth containing minerals (REE), vivianite, strengite,wavellite) present in pore networks; and3. as P occurring with iron oxides, in particular, goethite.However, the presence of secondary P-bearing phases does not contribute signifi cantly to the total P level in iron ore, and it is P associated mainly with goethite, which represents the most common occurrence of P in these ores.No direct evidence for the replacement of Fe by P within the structure of synthetic goethite has been demonstrated. Therefore, it is most likely that in iron ores P associates with goethite in occluded form as adsorbed PO4 3- species or as discrete P-bearing minerals, such as strengite, wavellite or vivianite, in ultra-fine, micro-pores or within intra-domain regions of multi-domainic goethite. Such occluded P is not easily extracted with commonly used lixiviants, such as weakly alkaline leachates. Recent development of a low temperature-alkalie/water leach extraction method has been successful in reducing not only the P content, but also amounts of Si and Al inthe initial ore. Refi nement of such a method to commercial application will have enormous benefit in realising the economic potential of large tonnages of high-P (ie >0.07 wt per cent P) bearing iron ore.

Jul 11, 2011

By Reinhardt Thiessen

UNDER sulfur in coal, is usually understood that form of sulfur which is combined with iron and known as pyrite. It occurs in the form of halls, lenses, nodules, continuous layers, thin sheets, or flakes, both in horizontal planes and vertical cleavage fissures. But pyrites also occur as very fine microscopic particles, or nodules, disseminated through the compact coal. This form has had but very little consideration. Finally, there is sulfur in coal in an amicroscopic form (not visible with an ordinary microscope), probably combined with the organic matter that exists -in tile coal. This form has had considerable attention from a scientific standpoint, but has probably not been recognized enough on the economic side. One or the other, or both, of these two latter forms may comprise the larger part of the sulfur content of coal, especially after it has been washed or otherwise prepared for use.

Jan 9, 1919

By R. O. Y. Breese

Perlite is a hydrated acid volcanic glass that has been derived from the alteration of obsidians through incorporation of water into the silica structure. It is distinguished from other members of the water-bearing natural glass family by total water content, characteristic fracture and luster. The distribution of major occurrences worldwide is associated with silicic Tertiary through early-mid Quaternary volcanics related to plate movement. The No Agua dome and flow complex is one of the most highly studied perlite occurrences in the world. It clearly exhibits lithologic and textural zonations that reflect simple cooling history. Similar features are commonly observed within other perlitized, extrusive glass selvages. This paper briefly discusses current thought regarding geologic occurrence, the hydration process and the modes of origin with special emphasis on No Agua.

Jan 1, 1985