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By Dragomir D. Kocic

At its lowest hierarchical level, the mine ventilation control system consists of local systems controlling the concentration of noxious gases in the air currents of various branches of the ventilation network, and of local systems controlling the air flow rates through those branches in which it is not necessary to regulate the concentration of any noxious gases. With respect to the noxious gas concentrations, the manipulated variables are air flow rates, while with respect to the air flow rates - the manipulated variables are aerodynamic resistances of the corresponding branches. Since there is an interdependence between the air flow rates in the ventilation network branches controlled through changes in aerodynamic resistance, the total system of mine ventilation control falls in the class of multivariable systems. The treatment of individual branches of a controlled ventilation network as separate plants presupposes an absolute autonomy of local systems, which is an untenable concept. The present paper is an attempt to break up the multivariable control system of the noxious gas concentrations and the air flow rates into autonomous (mutually unrelated) local control systems. The plant discussed is a ventilation network of arbitrary configuration with a single main axial fan. Because of the complexity of the problems involved, the multivariable control system of noxious gas concentrations and air flow rates has been described as linear, with constant and lumped parameters.

Jan 1, 1980

By Robert J. Timko, Edward D. Thimons, Robert L. Derick

In early June, 1986, a fire of unknown origin erupted in one of several main entries of a coal mine located in southwestern Colorado. The fire was aggressively fought with high- expansion foam. As a result of several strategic decisions, the fire appeared to be held in check. Unfortunately, sufficient quantities of foam were unavailable and as soon as the foam was depleted, control of the fire was lost. To prevent further damage and the possibility of an explosion, all entries to the mine were sealed. This paper recounts activities from the discovery of the fire to the initial reentry of the sealed mine including location of the fire, the decisions made to best combat it, and the steps taken to rapidly and securely seal the mine when this became necessary. The mine operator requested the Bureau's assistance in obtaining and analyzing mine fire gases taken from sampling ports placed through the mine seals. This report describes how samples were taken and what gases were analyzed. In addition, this work describes the initial exploration of the sealed mine by personnel using oxygen breathing apparatus.

Jan 1, 1987

By Ora H. Rostad

The sequence of events preceeding the discovery of the Mount Emmons molybdenite include some inadvertent near misses by several groups. The events are given in general chronological order to bring out the essentially contemporaneous, but different activities by several groups in two areas on opposite sides of Mount Emmons. The Mount Emmons molybdenite deposit lies in the Elk Mountain mining district. The west edge of the deposit is near the boundary between the Elk Mountain and Ruby mining districts as shown by the USGS map included (see Fig. 1). Considerable history regarding the Keystone silver-lead-zinc mine is given because of its proximity to the Mount Emmons molybdenite deposit which is on the other side of the mountain from Redwell Basin and where other significant activities took place. It should be noted that there was no documentary evidence available to me that would indicate that molybdenite was recognized to be present on, or under, any part of Mount Emmons, including Redwell Basin, before 1970. Veins containing silver-lead-zinc minerals were discovered in the Elk Mountain and Ruby mining districts about 1872. Some discoveries on the south flank of Mount Emmons about 1880 were developed into the Keystone mine. The Keystone has the largest cumulative production of metal ores of any of the mines in these districts. Most of the 413 Mt (455,473 st) of ore produced from the Keystone mine through August 1967 was produced after 1950. The ore averaged 175.4 gt (5.64 oz per ton) Ag, 2.62% Pb, 5.56% Zn, and 0.72% Cu.

Jan 1, 1991

By Ron L. Schmiermund

The Ferris-Haggarty underground mine was abandoned circa 1910, and portal discharge has since resulted in degradation of a trout fishery in the receiving waters of Haggarty Creek. Although tunnel discharge varies dramatically in volume throughout the year due to infiltration of snowmelt, compositionally it is a nearly constant low-TDS, pH-neutral, low-sulfate, copper-silicate dominated water. Between infiltration events, components of ARD accumulate in unsaturated, oxygenated environments within upper workings and are delivered to the main haulage level by the subsequent annual snowmelt flush. Mixing with non-ARD mine waters results in neutralization, dilution, and precipitation of amorphous copper carbonate and silicate phases. These mechanisms, combined with variations in the water balance, control the composition of the portal discharge. Understanding the chemical and hydrologic control mechanisms was critical to the design of a passive treatment system to decrease effluent copper concentrations.

Jan 1, 2000

By S. K. Mishra, S. B. Kanungo, D. Biswal

Jigging of the -2.8 +0.7-mm size fraction of a friable, low-grade manganese ore sample from Andhra Pradesh increased the Mn content of a concentrate by 7% to 8%, with an average recovery of 57%. The jig concentrate was mixed with the unjigged -0.7-mm size fraction and ground to -150 µm. The sample was then subjected to wet high-intensity magnetic separation (WHIMS). The magnetic fraction thus obtained showed an increase in Mn content of 6%, but with an overall recovery of only 50%. The results of hydrocyclone classification of -150- µm ground ore indicated that the method is not capable of upgrading the manganese content, as both ferromanganese oxides and aluminosilicate gangue minerals constitute the fine size fraction. However, when the nonmagnetic fraction obtained from the WHIMS of -150- µm ore is subjected to hydrocyclone classification and the underflow obtained is subjected to WHIMS again, an overall recovery of about 50% to 52% is obtained with at least a 7% to 8% increase in the Mn content of the product. The phosphorus content in the product is not reduced by either of the two combinations of methods. The complex association of phosphorus with all the major phases in the ore has been clearly demonstrated from the linear correlation between the distribution ratios of major constituent phases and phosphorus.

Jan 1, 2000

By S. J. Ripke

To pelletize fine moist magnetite concentrate, a 40% water slurry must be dewatered to about 10% by filtration, before it can be agglomerated into pellets. Slurry pH, typically ranging from 8 to 11, gives the magnetite particle surface a strong negative charge and thus causes two adverse effects. First, this negative charge attracts calcium and magnesium cations, which strongly retard the effectiveness of the bentonite clay binder added during agglomeration. Second, a repulsive force created by the negative charge functions as a dispersant that reduces filtering production rates. Tests were conducted to remove these cations during filtration, by rinsing the moisture remaining in the filter cake with a small amount of water adjusted to pH 6 with HCl. Laboratory work was also conducted at Michigan Technological University (MTU) and at Cliff’s Mining Services Company (CMSC) to corroborate the plant tests. In some cases HCl caused filter bag blinding, therefore CO2was investigated to reduce pH. The CMSC lab tests showed that using carbon dioxide to reduce slurry pH from 7.6 to 7.0 improved filtering production rates by 11%. Plant-scale filtering rates were improved by 23.7% when carbon dioxide addition reduced the slurry pH from 8.6 to 6.7.

Jan 1, 2004

By David J. Kruse

The proper modeling of granular flow using discontinuum mechanics has the potential to be one of the most significant scientific advancements in the mining industry today. This paper will examine the status of discrete element technology, specifically focusing on current and future applications. The fundamentals of the Discrete Element Method (DEM) will be briefly introduced, as well as relevant design parameters. Various types of granular flow problems currently being solved using the DEM methodology will be presented. The results and potential benefits of these cases will also be discussed. All simulation results and figures used throughout this paper are from studies and designs preformed by the DEM group at Conveyor Dynamics, Inc. (CDI).

Jan 1, 2000

By Joseph Kurtak

When prospectors discovered mineralized outcrops in Pine Creek Canyon in 1916, little did they know the site was destined to become one of the world's greatest tungsten mines. Located outside Bishop in California's rugged Sierra Nevada mountain range, the mine's development imposed unique challenges to the hardiest of mining men. In its early years, the Pine Creek operation was plagued by bad luck and poor timing. But through the perseverance of a dynamic group of mining personalities, it would gain world class status. Pine Creek tungsten supplied much of the defense needs of the United States during World War II and put the Bishop area on the map as a major contributor to the nation's stockpile of strategic metals. The mine's history was shaped by world politics, the ups and downs of metals demand and economic survival through technological innovations. In contrast to many mines, Pine Creek's workings went horizontally into and then up inside the mountains - nearly to the ridgetops. This resulted in the name "Mine in the Sky" being attached to the operation. The origin of Pine Creek's ore bodies is related to the emplacement of a portion of the Sierra Nevada batholith about 100 million years ago. During the intrusive process, granitic magmas engulfed overlying calcareous sedimentary rocks, flooding them with silica-rich hydrothermal fluids and metamorphosing them to skarn. The fluids also contained tungsten, molybdenum and copper. They precipitated as scheelite, molybdenite and chalcopyrite, respectively, during the metamorphic process. The ore-bearing skarns occur as near-vertical tabular pendants in the intrusive rocks. These were later exposed by the uplift of the Sierra Nevada mountain range and glacial erosion.

Jan 1, 1998

By Laurence M. Demers, Douglas C. Kuhn

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology which results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dub1 could influence the production of pro-inflammatory mediators in the lung environment. Rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500°C and 1100°C. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 and TxB2 production were markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 and TxB2 production. In vitro exposure of AM to untreated silica resulted in a significant increase in PGE2 and TxB2 production compared to control. However, exposure of AM to silica calcined to 1100°C resulted in eicosanoid levels which were not significantly different from control. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production.

Jan 1, 1991

By Steven J. Van Kauwenbergh, Talaat A. B. Lawendy

Batch laboratory-scale beneficiation tests were conducted on four high-iron phosphate samples. These samples included sedimentary ores (Tilemsi Valley, Mali and Tahoua, Niger), a sample from an igneous phosphate deposit (Matongo, Burundi), and a fine-grained phosphatic iron ore processing residue from Chile. The Matongo phosphate deposit occurs as a thick (up to 80 m) residual blanket of P205-enriched soil over solid parent rock (carbonatite and associated rock types). Although the Matongo deposit is an igneous deposit, ore from the deposit can be subjected to beneficiation treatments commonly used to treat sedimentary rocks. The beneficiation flowsheets designed to process these diverse ore types involve attrition scrubbing, size classification, and flotation. At the best flotation conditions tested, phosphate concentrates assaying 32.0%-39.0% P205 and 1.0%-1.5% Fe2O3, were obtained at 64.2%-82.2% overall P2O5 recoveries from run-of-mine (ROM) ores containing 9.2%-28.6% P205 and 5.9%-16.1% F,20,. A cleaner phosphate concentrate assaying 33.1% P205, 1.8% A1203, and 3.3% Fe2O3 at 53.4% overall P205 recovery was obtained from the phosphatic iron ore residue that originally contained 4.5% P205, 8.0% A1203, and 17.6% Fe2O3.

Jan 1, 1993

By W. G. Pariseau

Regression analysis of calculated on measured displacements were used to assess the influence of fill and fold plunge on shaft pillar mining at the Homestake Mine. These effects were neglected in the original three-dimensional finite element analysis undertaken in 1991. An average fold plunge of 15? and a 24K fill (Young’ modulus of 24,000 psi or 165 Mpa) were used in the reanalysis. Measured displacements were obtained from an array of 36 m (120 ft) multiple-position borehole extensometers installed in June 1994 and read to March 2003. Results indicate the effects of both on calculated displacements and thus on regression parameters are noticeable. However, these neglected effects would not have changed the original inference of Ross Shaft stability during pillar mining.

Jan 1, 2004

By G. Vik, P. Chryssanthakis, S. C. Bandis, L. Haruik, N. Barton, M. Christianson, A. Makurat

The large jointed chalk reservoir situated at 3 km depth in the North sea's Ekofisk field is undergoing major compaction after nearly 15 year of oil and gas production. Approximately 150 km 3 of the overlying sediments, mostly shales, are involved in the subsidence. A maximum central subsidence of nearly 3 meters, and a maximum present rate of 45 cm per year has set in motion numerous studies of the phenomenon. Non-linear finite element (FEM) and non- linear distict element (DEM) analyses of the compaction and large scale subsidence were performed. Consistent differences between the continuum and discontinuum analyses were noted. In the latter, slip on hypothetical bedding planes and sub- vertical or vertical faults was allowed, which possibly gives a more realistic simulation of the real processes of subsidence in such a large body of rock. Laboratory studies of the reservoir joints included roughness measurement, JRC and JCS characterization, direct shear tests while saturated in heated Ekofisk oil, and coupled closure-shear-flow tests with heated oil followed by heated sea water. Discontinuum modelling using Cundall's UDEC was performed on representative jointed assemblies (two sets of steeply dipping conjugate joints) to investigate the effect of a major reduction of pore pressure within the deformable matrix and along each joint. It was found that the large shrinkage deformation of the matrix allowed joint shearing to occur despite the constraint of uniaxial strain. Relative mass bulking due to small but widely distributed joint shear possibly explains the observed maintenance of excellent productivity despite large vertical strains in the reservoir.

Jan 1, 1986

By J. Loredo

Wastes related to abandoned mine sites can constitute important potential pollution sources, depending on their mineralogical and geochemical characteristics and volume. Mine waste disposal sites contain a diverse variety of wastes including overburden material and waste rocks, the ore which cannot be economically removed and wastes from the smelting processes when they are accomplished at the mine site. These materials are usually heterogeneous in size, mineralogy and metal concentrations. Asturias, in northern Spain, has an extensive mining history and, in consequence, there are abundant unreclaimed and derelict mine sites with abandoned mines and spoil heaps of different age, morphology, content and dimensions. In these spoil heaps, waste materials are subjected to the intense action of a humid environment, so the instability of sulphides and sulpharsenides results in the production of acid and metal-rich leachates, which are incorporated to surface water or infiltrated through the land reaching groundwater bodies. The mineralogical and geochemical characteristics of the stored materials are key data to evaluate if they represent an environmental risk. Mineralogy and geochemistry of wastes and the particular specific environmental conditions of each site affect the rate of weathering and therefore the metal release. The characterisation of mine wastes is a necessary step in order to establish suitable assessment strategies with the aim of reducing the leaching, transport and widespread of ecotoxic elements from mining wastes to the environment (surface water, sediments, soils and air). As a consequence of the weathering of As-rich mineral phases, high arsenic contents are commonly detected in effluents from mine voids and spoil heap leachates.

Jan 1, 2006

By L. F. Barrett, D. E. Cameron, J. C. Wilson

Exploration by Anaconda Minerals Co. in the Rico area from 1978 through 1983 resulted in dis¬covery of the Silver Creek molybdenum deposit. The drill-indicated resource is 40 Mt (44 million st) of 0.31% Mo, and projections suggest that the deposit may exceed 182 Mt (200 million st). No source intrusion has been intersected by drilling, but its presence is sugested by intramineral silicic alkali-alaskite porphyry dikes observed at the surface and in drill holes. Age dates and fluid inclusion studies indicate that the deposit was formed 5.2 ± 0.2 m.y. ago and that more than 1200 (3937 ft) of cover has since been removed by erosion. The deposit is hosted by Precambrian quartzite and greenstone, and Paleozoic sediments. Three prominent faults intersect in the vicinity of the molybdenum deposit, and one of these, the Last Chance fault, strongly influenced the shape and location of the deposit. The juxtaposition of host rocks across the Last Chance fault reflects significant offset spanning at least three different periods. Wallrock alteration associated with the deposit includes potassic, phyllic, and propylitic zones in noncalcareous rocks and garnet and anhydrite-diopside zones in the carbonates. All +0.2% Mo mineralization is within the potassic and garnet zones. Premineral faults that intersect the deposit contain the only surface molybdenum, tungsten, and fluorine anomalies. Dispersion halos of the indicator elements were defined by drilling in the discovery phase of exploration, and are particularly well-developed in the hanging wall of the Last Chance fault.

Jan 1, 1987

By Zsolt Csillag, Dragorad Ivankovic, Miomir Ceh, Anna Csordás-Tóth

Results of the common research work of ALUTERV-FKI and RI in field of ore dressing are presented here. Although monohydrate types of bauxites consist of finely dispersed minerals, however, in some cases certain contaminants (carbonates mainly), can be reduced by physical methods before Bayer process. Electronmicroscopy combined with computerized data processing is proven to determine the possibility of beneficiation and to control the different stages of ore dressing. Test results gained by Hungarian and Yougoslavian bauxite samples, contaminated by calcite, dolomite, siderite and pyrite, are discussed. Basic operations were: grinding (mostly dry) and classification, magnetic separation (mostly wet) and selective agglomeration. Only simple processes, having high efficiency and mostly dry ore dressing technique may meet the requirement of economical criteria. 1. [CONDITIONS OF ADAPTING THE BAUXITE DRESSING METHOD] Bauxite is a relatively cheap raw material, occurring in great bulks. Bauxite deposits may often lay far from the traditional ore processing plants, and in such cases the ore reaches the plants after long transportation. Some of these plants must face the difficulty that the resources of high quality ore are exhausted, they fall short of supply and, consequently, they must decide on whether to utilize the existing resources of poorer

Jan 1, 1984

By Frank Hagar, George M. L. Robinson

NTRODUCTION The Resource Conservation and Recovery Act and CERCLA (SUPERFUND), in many instances, has had an adverse economic impact on the hardrock mining industry. Over the last few years, many abandoned and active mining operations have been added to the Environmental Protection Agency (EPA) National Priority List (NPL) . When the property is placed on the NPL the operator or EPA is required to conduct extensive environmental assessments to determine if historical mining practices have degraded the existing environmental. If degradation has or will continue, the responsible party is required to implement appropriate remedial action plans. If a responsible party is not identified, the EPA implements a cleanup program. Experience has demonstrated abandoned and active mining operations are subject to RCRA, and possibly Super- fund, if the mine has not adopted appropriate hazardous waste disposal management procedures. If off-site contamination has occurred, the operator will be required to mitigate the impacts and will be required to adopt additional procedures to minimize future impacts. Since the passage of RCRA and Super- fund, many mining operators are adopting management procedures to monitor and inventory hazardous sub- stances and wastes generated, stored and disposed on site. Many operators are in a difficult position because ore, waste rock, process chemicals or other solid waste, in many instances, can be classified as hazardous waste. If the process or other solid waste is deemed to have the characteristics of a hazardous waste, the operator can inventory and adopt appropriate, in- expensive management procedures. However, if the ore or waste rock has hazardous waste characteristics, in- expensive control technologies are impossible to implement. Since existing statutes and regulations require hazardous waste control, the operator will be required to inventory, characterize and monitor all aspects of the mining operations including but not limited to exploration, mining, ore processing and waste disposal. During this process, geological, geotechnical, geochemical, waste and ore volumes, and process materials must be tracked throughout the mining process. To accomplish this task, the most cost effective method to maintain documented and accurate records, is through the implementation of an integrated database management system. The database management system can be used to model and simulate the entire mining operation and if necessary, used to predict whether the operation is in compliance with existing regulations. The developed database can also be used to operating optimize mining and disposal costs.

Jan 1, 1987

By S. Zendejas-Mendivil, E. Pérez-Segura

The Cananea porphyry copper-deposit is the site of the second largest mining operation in Mexico. Mineralization is related to quartz-monzonite Laramide stocks that intrude volcanic and volcaniclastic Mesozoic rocks. The ore deposit is a stockwork and breccia-pipes system with Cu-Mo sulfides and pervasive quartz-sericite hydrothermal alteration. A study was made of the arsenic distribution in the mine and the ore-dressing plants. The arsenic (As) in the mine is related to a feldspathic quartz-porphyry type rock associated mainly with the breccia pipe structures (100-700 ppm As in the Veta 7 Breccia). There is vertical zoning, with As decreasing in the deepest part of the breccias. This As mineralization corresponds to a later sulfide hydrothermal stage. The concentrates are made of Cu, Fe and Mo sulfides and some minor quantities of As minerals. The most important copper minerals are chalcocite-covellite, bornite and chalcopyrite. Some of these minerals have 390-880 ppm As. The main As mineral is enargite[ [Cu2.97Fe0.06(As0.90 Sb0.01Pb0 01 )0.92 S4 051 and there are traces of stibioluzonite-luzonite I Cu, .95(Aso.4vSbu.49)0.9rfS4.07-Cu2 93(Aso.H4Sba.10)0.94S4.13] and of another stibioluzonite mineral type with substitution of As by Bi[Cu,96(Ascr,,'Sb0ccrB'OJ3jI~6S] These minerals contribute 80% of the As in the concentrates.

Jan 1, 1992

By J de Cuyper, V. M. Lovell, W. Freyberger

The recovery of apatite from the phoscorite ores occurring in the Transvaal, Republic of South Africa, involves a flotation process that is particularly difficult to characterize from a fundamental point of view. However, the reagents used, (tall oil fatty acid, nonylphenyltetraglycol ether, sodium silicate, and sodium hydroxide) can successfully bring about a separation of apatite from dolomitic calcite, which is the most troublesome gangue component. Recently, it has been demonstrated with some flotation feeds that the addition of certain polysaccharides can improve the flotation significantly. It has been shown that the metallurgy obtained is closely linked to the nature of the froth, and this, in turn, is influenced, often dramatically, by the presence or absence of certain of the reagents. The character of the froth depends less on the inherent frothing ability of these reagents than on the presence or absence of fine mineral particles in the froth, and on their surface characteristics and state of aggregation. The polyglycol ether and the polysacchar- ides have been shown to affect these properties, and it is suggested that a major function of these reagents is to modulate the properties of the fine particles in the pulp, thereby changing the character of the froth and giving rise to improved results.

Jan 1, 1976

By C. J. Hall

An investigation of multi-shaft airflow problems by the author in 1976 (1) was presented in the hope of arousing considerable written comment, but in fact-. only one contribution (2) was forthcoming. The investigation in this paper is taken several stages fur¬ther, because the matter is of major importance in many American hard rock mines with complex networks extending over thousands of meters vertically. The examples used have all been generated thermodynamical¬ly and checked by motive column (denisty) calculations. Dry air has been used to reduce the amount of time spent on the rather complex calculations, but it has been shown (3) that the principals developed apply equally well to air/vapor/water mixtures. Initially the subject is investigated using both thermodynamic and motive column analyses. The latter part of the paper concentrates on a motive column presentation. Both methods are, of course, equally valid and give identical answers to any situation when correctly applied, as is shown in the worked examples.

Jan 1, 1980

By D. M. Avant, A. J. Solomon, S. M. Pickering, W. R. Fox

Introduction Most high purity silica is produced from crystalline quartz, generally from sand. However, there is a small area of southern Illinois where a porous, friable white chert rock is found that is very different in physical form from quartz sand. This microcrystalline material, commonly referred to as tripoli, is more easily ground to micron sizes than sand. Although of similar Moh's hardness, microcrystalline tripoli is less abrasive than either ground quartz sand or many synthetic abrasives. Location The southwestern corner of Illinois is underlain by extensive deposits of very porous chert; in some places the material is quite white. Two companies, Illinois Minerals Co. and Tammsco Inc., mine and process this white material. The Illinois Minerals plant is located at Elco, and the Tammsco plant is in Tamms, IL. Both companies mine from various locations within a 10-mile truck haul of their plants. Production from this district has been continuous since at least 1915. Malvern Minerals Co. mines and processes a generally similar microcrystalline, friable novaculite near Hot Springs, AR. Geology The southern Illinois white tripoli area is on the southern flank of the Illinois Basin. The commercial silica zone is a facies of the Clear Creek chert of Lower Devonian Age. To the north, where it occurs deep in the basin, the Clear Creek is a siliceous limestone. In the mining area, thin overburden has allowed access by surface ground water, which has leached away the carbonate content and left a quite pure silica residue. Fossils characteristic of sea bottom deposition, such as brachiopods and trilobites, are occasionally encountered in mining. The structure of the mining area is poorly known, due to infrequent outcrops. Strata in most mines are inclined at dips of 5° to 20°. There appear to be occasional high angle normal and reverse faults, but these are seldom of any significance in mining. The friable white silica zone mined in the Clear Creek chert is overlain by dark brownish-red chert and siliceous shale. Exploration drilling to date has not encountered the base of the microcrystalline tripolitic zone. Chemical content Leaching by ground water solution has removed virtually all the carbonate from the original siliceous limestone. Impurities encountered are red to yellow iron oxides, aluminous clays, and occasional black manganese oxides. The silica has no detectable formula water. A typical chemical analysis and physical properties are listed in Tables 1 and 2. Mineralogy and crystallinity Southern Illinois friable tripoli appears amorphous under the polarizing microscope. No crystal structure and only occasional, vague, patchy anisotropism is evident. However, the material gives an excellent quartz X-ray diffraction pattern. Thus, so far as X-ray mineralogy is concerned, the material is clearly

Jan 1, 1987