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By H. J. Rose

In a paper1 presented before this Institute in 1926,I briefly discussed the evaluation of coking coals by means of ultimate analysis. The paper contained several graphic studies in which coal analyses calculated free of moisture, ash, sulfur and nitrogen were plotted on triaxial diagrams in which carbon + hydrogen + oxygen = 100 per cent. From a study of such data for 600 coking coals of the United States, and 150 coking coals of Wales, France and Germany, it was concluded that it was usually possible to predict coking properties and by-product yields with fair success from ultimate analysis. The coals which have proved exceptions to the general rules were found to have physical peculiarities. Run-of-mine Coal It must not be forgotten that run-of-mine coal is a composite material consisting of many constituents differing in physical properties and chemical analysis. A coal sample usually contains: 1. Glossy black coal known as anthraxylon or vitrain. This constituent usually has the strongest coking properties, and the lowest ash content. 2. Dull black coal consisting of attritus containing thin layers of anthraxylon. It is also known as clarain. This constituent, in a coking coal, usually has good to excellent coking properties. 3. Mineral charcoal or fusain. This is a porous black material which is soft and crumbly (unless impregnated with mineral matter) and which has absolutely no coking properties. It is different in every respect from the other constituents in coal. The volatile matter content of mineral charcoal is less than 20 per cent. even when it is associated with high-volatile coals. As would be expected the hydrogen content is low, and the carbon content is high. 4. A coal sample may contain tough gray canneloid material which has a high-volatile matter and a high hydrogen content, but is poor in coking qualities.

Jan 1, 1930

Statistics compiled by the United States Geological Survey show that the iron ore mined in the United States in 1917 reached a total of 75,288,851 gross tons, exceeding the former record output of 1916 by 121,179 tons. The shipments from the mines in 1917 were 75, 573,181 gross tons, valued at $238,260,333, a decrease in quantity of 2,297,372 tons, or 2.95 per cent., and an increase in value of $56,358,056, or 30.98 per cent., over the shipments in 1916. The average value per ton at the mines for all grades of ore in 1917 was $3.15 as against $2.34 in 1916. Stocks of iron ore at mines, mainly in Minnesota and Michigan, amounted at the close of 1917 to 10,628,908 gross tons, compared with 10,876,352 gross tons in 1916. The quantity of pig iron, exclusive of ferro-alloys, sold or used in 1917, according to reports of producers to the United States Geological Survey, amounted to 38,612,546 gross tons, valued at $1,053,785,975; compared with 39,126,324 gross tons, valued at $663,478,118 in 1916, a decrease of 1.32 per cent. in quantity and an increase of 59 per cent. in value. The average price per ton at furnaces in 1917, as reported to the Survey, was $27.29, compared with $16.96 in 1916, an increase of 61 per cent. The production of pig iron, including ferro-alloys, was 38,647,397 gross tons in 1917, compared with 39,434,797 gross tons in 1916, a decrease of 4.5 per cent., according to figures published by the American Iron and Steel Institute, March 18, 1918.

Jan 12, 1918

By Charles Frey

TIE fundamental principle of resistance thermometry lies in the determination of temperatures by the measurement of an electrical conductor subjected to various temperatures and the translation of the resultant changes, in ohms, into temperature equivalents. Such resistance measurements can be made with maximum precision by the use of a standard Wheatstone bridge and a reflecting galvanometer of high sensitivity. Under such conditions, results are obtainable that may be accurate within 0.1 or even 0.01 per cent., and the "idiosyncrasies" of heated electrical conductors can be studied with advantage and profit, even if the latter is not of a financial nature. The chief requisites for producing a serviceable -commercial instrument may be enumerated as follows: First, there must be a resistor or "bulb" that can stand the maximum temperature without deterioration and which has a pronounced temperature coefficient. Second, there should be constructed an "even" bridge, having two fixed arms of equal values, in ohms. Third, a rheostat, the maximum resistance of which will be equal to the total change in the resistance of the bulb, between temperature extremes, is required. Fourth, there must be a sensitive galvanometer which is aperiodic, or nearly so. Finally, there should be a fairly steady source of direct current. The general scheme of this type of apparatus, in its simplest form, can be readily understood by reference to Fig. 1. Resistors A and B are constructed of manganin, therlo, or some other resistance wire having a negligible temperature coefficient. The sensitive D'Arsonval galvanometer G has its zero in the center. R is a rheostat and X is a resistor or bulb made of insulated platinum wire, or else of nickel, copper, or some alloy, according to requirements. K is a battery, but a direct-current service line is often used instead, with sufficient ballast in series to properly reduce the current.

Jan 8, 1919

By F. E. Minshall

FoR more than 30 years California has been one of the three leading oil-producing states. Present daily production of crude oil under curtailment, approximately 580,000 bbl., comes from three general areas: Los Angeles Basin, San Joaquin Valley, and the coastal region of Ventura and Santa Barbara Counties. This state produces approximately two-thirds of its oil from eight large fields, and obtains a daily average production of 48 bbl. of oil per producing well, whereas the average for the United States is but 8.15 barrels. During the closing stages of the first half of 1936, discovery of the Section Ten oil field was made, and credit goes solely to geophysical work. It is the first direct important discovery of oil in California that may be credited to geophysics. This discovery may furnish the cue to the means of discovering several fields in California, particularly in the San Joaquin Valley. It is a question, however, whether returns from geophysical work will play as important a part in the future supply of oil in California as have our former types of prospecting. Explobation Methods of prospecting have progressed in the oil industry through invention or improvement in scientific means of locating and defining structure and because of market improvements in drilling equipment. Present methods of prospecting include: 1. A detailed study of geology in an attempt to locate structural and stratigraphic conditions that would be favorable to the accumulation of oil. 2. Geophysical methods involving the use of the seismograph, torsion balance, magnetometer and electrical methods. (There is still much to be learned in California in the application of geophysical methods.) 3. Use of micropaleontology as an aid in correlation,. The principal improvements in drilling equipment are: 1. The Schlumberger dipmeter, which determines the direction of formation dip in an uncased hole.

Jan 1, 1937

By William R. Rumbold

When I was in South Africa during the latter part of 1904, there were three known tin-fields, which may be called the Cape Town, the Bushveld, and the Swaziland fields. The Cape Town Tin-Field. This district is situated near Kuils river, 20 miles west of Cape Town, and 5 miles from Kuils River station on the Cape Town & Stellenbosch railway. The deposits are in granite, intrusive in the Malmesbury beds, which are supposed to be of Silurian or Cambrian age. The granite, resisting denudation better than the surrounding shales, has formed low-lying hills, the highest of which, the Bottlelary Berg, is 1,510 ft. above sea-level. The rock consists of quartz, orthoclase feldspar, and biotite mica; tourmaline is also present. The feldspar occurs in large crystals. The rock is generally decomposed on the surface, and the decomposition sometimes extends as deep as 100 ft. This formation—granite intrusive in Silurian shales— extends for many miles to the northeast, but so far as I know the Kuils River deposits are the only ones now known to occur in it, though probably further prospecting will reveal other deposits. This particular discovery was accidental; alluvial tin being found in the course of boring for oil. The Kuils River Deposit. This deposit comprises both lode and alluvial tin. The lode strikes N-S., and dips about 30' E. into the hill. It is 5 ft. wide, and composed of dense white quartz, in which pinkish-gray cassiterite is distributed in large crystals. The vein also contains considerable quantities of wolframite. Fig. 1 is a rough plan of the relative positions of the lode and the alluvial deposit, the latter, as shown, following the course of a stream, while the lode crops out on the hillside ,

Jan 1, 1909

By John Roberts

THE Federal income tax law permits as a deduction in determining net income "in the case of mines, . . . a reasonable allowance for depletion and for depreciation of improvements, according to the, peculiar conditions in each case, based upon cost, including cost of development not otherwise deducted: Provided, that in the case of such properties acquired prior to Mar. 1, 1913, the fair market value of the property (or the taxpayer's interest therein) on that date shall be taken in lieu of cost up to that date." The law provides for a reasonable allowance but the regulations provide for a definite method of computation that possesses more the virtue of simplicity than that of reasonableness. Article 210 of Regulations 45. reads: "When the cost or value as of Mar. 1, 1913, or within 30 days after the date of discovery of the property shall have been determined, and the number of mineral units in the property as of the date of acquisition or valuation shall have been estimated, the division of the former amount by the latter figure will give the unit value for purposes of depletion, and the depletion allowance for the taxable year may be computed by multiplying such unit value by the number of units of mineral extracted during the year." This is simple, but is it reasonable? The intent of the law is clearly that the cost of the ore in the ground shall be considered as part of the cost of the same ore when removed and sold. The regulations fail to carry out that intent, because of the unwarranted assumption that all the ore in the mine cost the same amount per ton. This is what gives the Treasury Department's method its simplicity, but at the same time robs it of its reasonableness because the assumption is contrary to fact.

Jan 1, 1921

By E. G. Banks

This paper is presented in the belief that metallurgists and chemists will be interested in the practice of grinding in tube-mills in connection with stamps, especially since the records of working here given extend over a lengthy period of time (since May, 1905). The ore from the Waihi mine—more especially that produced in the upper levels—contains a large proportion of hard, chalce-donic quartz, and the gold exists in an exceedingly fine state, conditions which necessitate very fine crushing in order to obtain a high extraction of the precious metal. Before the introduction of tube-mills at the 90-stamp Waihi mill, it was found necessary to stamp through 40-mesh (1,600 holes per sq. in.) woven wire-screens, having a fairly high discharge. The pulp then graded : Per Cent. Per Cent. On 50-mes11, .- 0.1 On l20-mesh ..8.77 On 60-mesh, . 8-74 On 150-mesh,.... 7.48 On 80-mesh,... 16.06 Passed 150-mesh,... 55.19 On 100-mesh,.... 3.66 The stamp-dnty was 2.89 short tons per stamp per day, or a total of 260 tons daily. Although the extraction on this pulp was: gold, from 88 to 90 per cent., and silver, from 74 to 78 per cent., it was recognized that finer grinding of the sands would prove beneficial, provided a machine could be found to do this work economically. Various grinding-mills and pans were tried, but without satisfactory results, the particles of sand being so hard that the capacity of any of the machines was too small to be economical. The results of grinding in tube-mills in other countries were so satisfactory that three tube-mills mere erected at the Waihi

Jan 1, 1908

For convenience, we tabulate below the weight systems contained in the Probierbüchlein: [Pound and centner weights used by merchants for ore, lead, and copper I frother = 20 or 50 centners (depending on locality) I centner (Stolberg & Eisleben) = 112 pounds. I centner (Nuremberg) =100 pounds I pound =2 marks =32 lot =128 quintlein-512 pennyweights =1024 beller I mark -16 lot -.64 quintlein =256 pennyweights = 512 beller 1 lot= 4 quintlein= 16 pennyweights= 32 beller I quintlein = 4 pennyweights= 8 beller I pennyweight = 2 beller Netherlands mintmasters' weights for silver I mark =12 pennyweights=288 grains I pennyweight - 24 grains Assay weights for gold I mark= 24 carats 96 carat-grains. I carat = 4 carat-grains] The assayer's weights were miniature copies of the legal weights of his locality, intended, like the modern assay ton, to eliminate calculation. Each assayer made his own, not usually bothering about a given proportion between the true weights and the assay set, but maintaining the correct ratio between all the weights in any one set. The weights were quite small, to permit the use of less sample, but the exact size is nowhere stated in the Probierbüchlein. Even the legal pound varied considerably from place to place, depending on locality, and assayers would use different factors depending on the sensitivity of their balances, among other things. Agricola makes the assay centner equal to one actual drachma, by which term he means the German quintlein, or 1/12,800 of the full weight of the 100-pound centner. Schreittmann says that the 100-pound centner on the assay scale should be less than half a quintlein, i.e., the factor should be at least 25,600. Biringuccio says the assay centner might

Jan 1, 1949

Iowa Geological Survey, Des Momes, Ia. George F. Kay, State Geologist A list of publications will be sent upon request Most of the papers of the Survey have been published in the Annual Reports, issued since 1892. Separates of the many papers in the Reports may be had for postage, except where they are out of print, and except for vol 1 (1892), 2 (1894) and 14 (1903), where no separates are to be had. Thirty-five Annual Reports have been issued up to and including vol 35 (1929). A charge, plus postage, is made for vols, 4, 5, 7, 8, 9, 10, 28 and 33, others will be sent free upon request, plus postage on from 2 to 6 pounds Space prohibits giving more than a general picture of some of the contents; vols 4, 5, 7, 8, 9, 10, 11, 12, 13, 15, 16, 20, 27, 32, contain, among others, papers on the geology of Iowa, by counties Vol. 19 (1908), 6 lb , contains a number of papers dealing with the peats and coals of Iowa, and has bibliographies of those subjects Vol 22 (1912), 6 lb , contains an annotated bibliography of Iowa geology Vol-24 (1913), 6 lb , contains the analyses of 16 Iowa coals Vol 28 (1917, 1918), price $1 50, 4 lb , completely covers the subject of gypsum in Iowa, and has a bibliography of the sub¬ject. Each volume carries an administrative report and a review of mineral production for the period covered In addition, Technical Paper 2 (1930), Studies of Iowa coals, will be sent free upon request Also a geological map of Iowa, and maps of Iowa showing the distribution of the glacial drift sheets throughout the state, have been issued and are available

Jan 1, 1933

By Frank C. Greene

The principal event in the development of oil and gas in Missouri in 1942 was the drilling of the Cities Service Oil Company's No. I Jim Cook, in the northwest corner, NW. 1/4 sec. 32, T. 65 N., R. 39 W., Atchison County, in the northwest corner of Missouri. This well, not yet completed, bailed several barrels of free oil in about 27° Baume from a sand called the Bartlesville by those in charge, at a depth of 1450 ft. The well is on a block of leases obtained after the area, which is covered by several hundred feet of glacial drift, had been prospected by core drilling. Earlier in the year the same company drilled a well on the Glen Gray farm in the southwest corner, SW. 1/4 sec. 29, T. 65 N., R. 39 w., to a depth of 2427 ft. in the Hunton lime with a rotary drill. Oil stains in this hole led to the drilling of the second well. Table i .—-Wells Drilled for Oil and Gas in Missouri in 1942 Country Number of Number of County Oil Wells Gas Wells Dry Andrew.......... Atchison.......... I Bates............ 2 6 Caldwell.......... I 3 Cass............. I Clinton........... I Holt............. I Jackson.......... I I Knox............ I Nodaway......... I Platte............ 4 4 Ray.............. 5 Sullivan.......... I Totals.......... I 7 28 Otherwise drilling in Missouri was uneventful, with a total of only 36 Completions, of which one was a very small oil well, Seven were small gas wells and 28 were dry holes. The total footage drilled was 24,7541/2 ft., of which 14,0281/2 was by cable tools and 10,726 ft. by rotary. Twelve of the dry holes were drilled into Mississip-pian or older beds. Table I gives a summary of activities by counties.

Jan 1, 1943

The Colorado Scientific Society, Denver, Colo Charles Henderson, President, 519 U. S Custom House, Denver, Colo. Beginning in 1882, up to. about 1919, the Society published 11 volumes containing many valuable papers From the informa¬tion at hand, the papers in those volumes are now only available in libraries or on file at institutions. Vols 12 and 13 are the current volumes, and the list of the geologic papers contained in them are given here For any information as to price and availa¬bility, address the above. Vol 12 (1929-31) No 1, The geology of the Sangre de Cristo Mountains, by J H Johnson, 2, Relation of the ore deposits of the southern Rocky Mountain region to the Colorado Plateau, by B S Butler; 3, Mosquito Range and the Leadville district, by C H Behre, Jr , 4, Geologic history of the Front Range, by T S Lovering, 6, Revision of geologic structure and stratigraphy in the Ouray district, by W S Burbank, 7, Localization of ore in the schists and gneisses of the Mineral Belt of the Front Range, by T. S. Lovering, 8, Relation of the ore deposits of the southern Rocky Mountain region to the Colorado Plateau, by J. B. Tenney; 9, Preliminary geologic map of the Alma mining district, by Q D. Singewald and B S Butler, 10, The Climax molybdenum deposits of Colorado, by B S Butler and J W. Vanderwilt, 12, Localization of ore bodies at Rico and Red Mountain, by G. F Collins, and Geology of Mount Lincoln and Russia mines, by Q D Singewald and B S. Butler. Vol 13 (1932- ): No. 1, Preliminary geologic notes on Galena Mountain, by J. W Vanderwilt, and High plains of Colorado and New Mexico (Late Tertiary history), by F. M. Van Yuyl and J M. Coke

Jan 1, 1933

J. S. UNGER, ? Pittsburgh, Pa. (written discussion ?).-Firebricks intended for, the same purpose, but supplied by different manufacturers, may be of entirely different clays, contain different proportions of flint, calcined and plastic clays; the particles may vary widely in size; the water used to make the brick will vary; the pressure in molding will vary, depend-ing on whether the brick is hand made or power pressed; and the degree of burning in the same kiln will differ. These variables affect the melting point and the strength of the brick when heated. An important property, of a firebrick is its ability to resist heat and, at the same time, weight or load without serious deformation. The soft-ening point and the melting point of a firebrick may be several hundred degrees apart, and two bricks may show considerable difference in their softening points, but the melting points may be approximately the same. Bricks are not usually employed at temperatures close to their melting points. If they must withstand very high temperatures, the firebrick is discarded and a brick of more refractory material is used. Under these conditions' it is doubtful whether the determination of the melting point of a brick has much practical value. If the determination of the melting point is necessary, the test should he made on a portion of the original brick and not on a specially prepared sample. A small triangular pyramid with a base about 1 1/2 in. and 3 in. high can be sawed from the corner of the brick with a thin-bladed car-borundum wheel, without injuring or destroying the size of particles, the bond, or degree of burning of the original brick. This specimen can then he compared with standard Seger cones or tested by any other method desired.

Jan 12, 1919

By Frank C. Greene

The principal event in the development of oil and gas in Missouri in 1942 was the drilling of the Cities Service Oil Company's No. I Jim Cook, in the northwest corner, NW. 1/4 sec. 32, T. 65 N., R. 39 W., Atchison County, in the northwest corner of Missouri. This well, not yet completed, bailed several barrels of free oil in about 27° Baume from a sand called the Bartlesville by those in charge, at a depth of 1450 ft. The well is on a block of leases obtained after the area, which is covered by several hundred feet of glacial drift, had been prospected by core drilling. Earlier in the year the same company drilled a well on the Glen Gray farm in the southwest corner, SW. 1/4 sec. 29, T. 65 N., R. 39 w., to a depth of 2427 ft. in the Hunton lime with a rotary drill. Oil stains in this hole led to the drilling of the second well. Table i .—-Wells Drilled for Oil and Gas in Missouri in 1942 Country Number of Number of County Oil Wells Gas Wells Dry Andrew.......... Atchison.......... I Bates............ 2 6 Caldwell.......... I 3 Cass............. I Clinton........... I Holt............. I Jackson.......... I I Knox............ I Nodaway......... I Platte............ 4 4 Ray.............. 5 Sullivan.......... I Totals.......... I 7 28 Otherwise drilling in Missouri was uneventful, with a total of only 36 Completions, of which one was a very small oil well, Seven were small gas wells and 28 were dry holes. The total footage drilled was 24,7541/2 ft., of which 14,0281/2 was by cable tools and 10,726 ft. by rotary. Twelve of the dry holes were drilled into Mississip-pian or older beds. Table I gives a summary of activities by counties.

Jan 1, 1943

Meeting, Oct. -04, 1913.-The sum of $1,250 was directed to be sent to the International Engineering Congress, 1915, in accordance with the terns of the Institute's guarantee. It was voted to request the several Technical Committees to recommend names of their members as sub-chairmen and members of sub-committees to co-operate with the Bureau of Mines. The Finance Committee was empowered to send all members in arrears a notice that the provisions of the Constitution, by which they cease to hold the privileges of membership if their dues are not paid by Jan. 1, 1914, become operative on that date, unless the Directors vote to extend the time in each individual case. The report of the Nominating Committee, printed on page i, was accepted. It was voted that a notice to be prepared by the Committee on Increase of Membership and an application blank for membership be printed in the front of each Bulletin. The report of the Committee on Patent Law Legislation was adopted and the Committee discharged. The Budget of the Chairman and the Secretary-Treasurer of the Colorado Local Section for the balance of the present calendar year was accepted and an appropriation of $47.75 made to them. Upon the nomination of two members of the Committee on Honorary Members, backed by 13 members of the Institute who are not members of the Board of Directors, Dr. Frank Dawson Adams, of Canada, was unanimously elected an Honorary Member of the Institute. Upon the nomination of two members of the Committee on Honorary Members, backed by 11 members of the Institute who are not members of the Board of Directors, Mr. Ezequiel Ordoñez, of Mexico, was unanimously elected an Honorary Member of the Institute.

Jan 11, 1913

By F. L. Grammer

The analyses given in Table I. were made several years ago at my request at a plant using Lake ores. They are of two furnaces, one making basic, the other Bessemer pig— they gave 6 casts each in 24 hr., also two flushes of cinder between each cast. They are offered simply for the sake of reference as, so far as I know, it is unusual to find so frequent full analyses made and none are on record. The variations in manganese-content in the first and second flushes on the basic furnace are interesting, if no more than a freak—the first flush being invariably higher in manganese. The iron-content of the two slags from an average of 12 flushes shows: Basic. Bessemer. Per Cent. Per Cent. Total iron...................................... 2.85 1.70 Combined iron................................ 0.72 0.52 Free iron....................................... 2.13 1.18 The greater iron-loss in the basic slag, while known, has never heretofore been so clearly set forth. This may modify the arrangement for handling slag; heretofore usually determined by proximity of the dumping-heap. If a nearby heap is used on contiguous territory, in the past, tilting molten-slag pots were used. If the Pittsburg flood-records for 30 years are a fair criterion the government regulations were inadequate, and molten slag was dumped in such a manner as to throttle the Monongahela at the time of the spring thaws. At Pittsburg the slag, where it is carried to a distance, is frequently granulated in pits and then removed in cars to which it is conveyed by clam-shell buckets. This practice is also quite customary where the slag is intended for the manufacture of slag cement. The production of 500 tons of cast-iron daily means about 300 tons of- slag and at 2.113 per cent. equals 6.4 tons

Jan 1, 1914

By Bennett R. Bates

Nowhere in the world has cone classification in closed-circuit grinding with tube mills reached as high a state of development as on the Wit-watersrand. In the development of the Far East section the necessity of fine grinding to obtain satisfactory residues gave rise to a situation with which the cone could cope only at a great sacrifice in efficiency of tube-mill grinding. H. A. White1 recognized the limitation of the cone in his study of the theory of tube milling as early as 1915, but it was not until Ewing, Davis and Willey2 carried out their tests at Springs Mines during 1920 that the advantages of mechanical classifiers were demonstrated. During the fall of 1924 the writer supervised a series of tests with Dorr classifiers undertaken by Mr. White, Consulting Metallurgist, at the mill of the Geduld Proprietary Mines, Ltd., Dersley, Transvaal (Far East Rand). The importance of classification to obtain efficient tube-mill grinding was thoroughly demonstrated. The installation of classifiers of the above type that followed the test confirmed the results of the experimental work. Tests with Cones, Straight Type and Bowl Classifiers The test at the Geduld mill was made to determine the relative grinding efficiency of a tube mill when grinding in closed circuit with cones, straight type Dorr classifier and Dorr bowl classifier. The efficiency of a tube mill, as expressed in this article, is based on the tons of minus 200-mesh material produced by the mill. The efficiency is also expressed in terms of tons of minus 90-mesh material produced by the mills to correspond to the standard practice on the Witwatersrand. The results given for the performance of the tube mills grinding in closed circuit with cones (Fig. 1) were taken from previous tests carried

Jan 1, 1926

By Herbert Haas

1. INTRODUCTION COPPER matte is now converted into blister copper at a cost of only $5 per ton of copper, or, based on a 40 per cent. matte, $2 per ton of matte, which is the record of at least one large smelting Works; and it seems hardly likely that a further reduction, large enough to warrant, a change in existing practice, could be made in bessemerizing costs. But the new type of converter here described and the new practice proposed are intended, not so much for the treatment of mattes, as for the extension of, the process to the direct reduction in the copper-converter of pyrite ores

Jan 6, 1914

By C. L. Pillar

TWO shafts have been completed since the spring of 1948 when underground development started, and three are now under construction. The new program provides two main ore shafts, Nos. 3A and 3B, spaced 195 ft apart and located on the south- western end of the orebody. It is planned that eventually 35,000 tons of copper ore per day will be hoisted by these identical four-compartment shafts. The third shaft of this new group is 600 ft from the present No. 1 shaft and will provide caged sup- plies for the underground mining operations. This No. 4 shaft has the largest cross-section of any shaft in Arizona.

Jan 7, 1954

By A. Blake Caldwell

Northwest frontier is here defined as Alaska, the Yukon, the Northwest Territories and northern British Columbia. The mineral potential of this area is great and will unfold in the decade ahead but now the largest single producer is the Pine Point lead-zinc mine in the NWT about 1200 km north of Edmonton, Alta., close to the south shore of Great Slave Lake. The mill, initially designed for 4540 mtpd, was expanded to 7250 mtpd in 1969. This operation is described in detail in Mining and Concentrating of Lead and Zinc, Vol.1, Chapt. 17, SME/AIME in the article by W. H. R. Gibney.

Jan 1, 1971

By Joseph Pogue

THE writer visited the Muzo emerald mines in July, 1915, and spent six days in their study. This paper embodies the results of his observations, plus information personally communicated by Robert Scheibe, FIG. 1.-SKETCH MAP SHOWING APPROXIMATE LOCATIONS OF ALL IMPORTANT EMERALD MINES AND PROSPECTS IN COLOMBIA. (Data in part supplied by Robert Scheibe, July, 1915.) Professor of Geology in the Mining Academy of Berlin, who at the time of the visit was completing a detailed field investigation of nearly a year's duration of the emerald deposits of Colombia. An elaborate account of this valuable work may be expected at a future date from the pen of Professor Scheibe.

Jan 5, 1916