Volume 06-07 (1862-1863) (510 pages)

MINING AND SCIENTIFLE PRESSe [From Tze Loxpox “ Maing axD SMELTING MaGazine.”?] THE MEXICAN METHOD OF AMALGAMATION. BY JAMES NAPIER, JUN., F.C.S. Late Clicmist and Assayer to the Guanaxuato Mint, Mexico. INTRODUCTION, Before proceeding to describe in detail the Mexican method of amalgamating silver ores—which will principally apply to those which came under my own observation at Guasaxuato—I propose making a few introductory remarks on the history of the Pa'io amalgamation process, and on the composition of the ores charastzristic of some of the different districts. The ancients were well acquainted with the property which mercury has for-combining with gold and silver, and took advantagé of the fact for romoving gold from. old apparel by first burning them to ashes in an earthern pot and then amalgamating them. Humboldt also states that, before the discovery of Aierica,the Germans employed mereury to extract gold from auriferous sands as we!l as from iron and copper pyrites ; but we have ne knowledge of mereury having been employed for the purpose of extracting silver from its ores before the year 1557, when Bartolome Medina, a miner of Pachuca, in the neighborhood or Real del Monte, in Mexico, discovered the “Patio” method of amalgamation. It is very difficult to form any correct idea as to *how this wonderful process was invented, and whatit was that led to the discovery. It could not have been by chemical reasoning that Medina mixed the various ingredients—sulphate of copper, (magistral) salt and mereury— with the minerals of silver to extract the metal; and the discovery appears most extraordinary when we consider that the process requires weeks aud even months for its completion, so that a long time had to elapse before the result of ‘an experiment could be obtained. We can only suppose that Medina, being aware of the property which mercury has of combining with silver and forming amalgam—and also knowing that anhydrous sulphate of copper (obtained by calcining copper pyrites) when immersed in water gives out heat—conceived that if these were mixed with silver ore and common salt (which was thought to have a cleaning effect on the silver previ us to its combining with the mercury), that the heat caused by the sulphate of copper would favour the amalgamation. Although this process requires a long time for its completion, the operation of reduction commences almost at once, so that by taking out trials soon after the incorporation of the mass.it could be seen that the mercury was taking up silver ; and it would be easy to know, by burning at intervals a weighed portion of the amalgam, how much silver the whole qauntity of mercury added would contain, and when the process was completed. In 1586, 2 Peruvian miver of the name of Carlos Corso de Leca discovered what has been termed “el beneficio de hierro” (the reduction by irou.) This consisted in adding to the torta small pieces of metalic iron, the object of which -was to save mercury, which it would do by reducing the chloride of silver ; but Iam not aware of this process ever having been worked to any extent. The next improvement made was by Alonzo Barba, in "1590. It consisted in amalgamation in large copper pans, heated from below, and was called ‘‘el beneficio de caso y cocimienio.” In this process there was a great saving of mercury, but a large consumption of copper, as the chloride of silver was reduced at the expense of the copper pans; if answers very well for the native chlorides, but not for sulphides of siver. In 1784,this process was introduced into Europe by Baron de Born, au Austrian mining officer, and from it has sprang the barrel amalgamation of Frieberg, proposed, I believe, by Gellert. So that from the process first invented by Madina, in Mexieo, has sprung all others for amalgamating silver ores ; and although his original process has undergone many alterations, the principle still remains the same. SILVER ORES OF A FEW OF THE DISTRICTS OF MEXICO. I helieve that every known ore of silver has been met with in some one or otherof the numerous mineral districts of Mexico, but many districts have ores peculiar to themselves, and all ores will not yield their silver by the “patio” amalgamation. Perhaps the ores of Guanaxuaio yield their silver by the patio anunlgamation better than those of other districts,. from the fact of their containing but few foreign metals ; the silver being mostly found in the form of pure sulplides, in many instances’‘in carbonate of lime and quartz veins. The following shows an analysis of ore from the district of “La Luz,” in Guanaxuato :— Silver. Tron 5. . <ee eee 4,71 Carbonate of limes. .-=8.25 magnecia. 3.26 Sulphiay.i.. gees 6.79 Copper. ...oa 55 99.60 This, however, is not to be considered hy any means as an average sample of ore from this district, for the average richness of the ores produced here will probably not exceed from 45 to 60 ounces of silver per ton. Nearly the whole of the ores of this locality contain gold in various proportions. To show what proportion the gold bears to the silver, we suhjoin the coinage of the mint of Guanaxuato for ten years, commencing at 1850. Coinage or Tur Guanaxvato Mint ror 10 years. Fay Te Ter Cent Year. Gold $ Silver $ Total $ of Gold 1850 709,472 7,801,300 8,510,772 8,336 1951 606,022 7,011,750 7,617,772 7.955 1852 746,956 7,625,650 8, 372,606 8.921 1853 723,078 6,235,922 6,969,000 10.375 1854 450,288 §,029,712 5,480,000 8.216 1855 555,200 4,698,800 5,254,000 10.567 1856 79,476 4,306,524 4,786,000 10.018 1857 570,700 4,747,300 5,318,000 10.731 1858 489,744 4,725,256 5,215,000 9.391 1859 438,8°0 5,046,120 5,485,000 8.001 The ores of Zacatecas frequently contain argentiferous blende, which makes them rather more difficult to work than those of Guannaxuato. Gold was almost unkuown in the mines of Zacatecas until 1856, when a vein was cut in the mine of the “Bote” containing large quantities of gold, which still continues to yield a considerable produce of that metal. Real del Monte produces ores of a very various nature, some containing considerable quantities of maganese ; as the following analysis of a sample by Mr. Rogers, from Santa Brigida vein in that district, will show :-— BGs dices ss eee evewes AP Gr Oro +++ -68.00 WAURITIN Gels; e apaisteleyel ele mies +) «)5 © SELES 6.00 Peroxide and sulphide of iron.. 7.50 JWAAED Donoso ocoupennccococgitibo oc 1.60 Sulphide 0188 GAG seam condbooonccs.n0 2.82 Peroxide of manganese.... 5.30 Sulplideof Zinc . sass 1 <> sel snee « 2.30 MUINIG «seeped < « c cieleletdiars + Wie nis/eieis 1.45 Dulphide Of Copper..5-.--.40 fap Saeco COC RGAE ooo Seo ape oog 25 Potash, antimony, tellurium, traces of soda, gold and loss.. ier ouaue 2.38 100.00 My late lamented friend Mr. Edward Louckner, who has examined these and similar ores very carefully, states that the silver in many cases exists ag a manganate. The ore from the various mines of this locality differ very much in their nature and composition, and have consequently to be . reduced by different methods: some are reduced by patio, others by barrel amalgamation, and some are smelted, Some of the silver produced here contains sufficient gold to make its extraction a matter of importance. In the district of Angangueo the silver exists mostly combined with bl-nde and sulphide of lead, and is reduced bysmelting. The following analysis shows its composition : CATT Ot ei ong 52.09 SUDO Ut ee sci 2. .32.00 TOU Mele 2 cia/c/efe'= 70 ~ aie 13.44 ‘Antimony =. 22). << 2.40 DUVER ec ee ecu se eee ny 100.90 In Fresnillo the ores workeddono not perhaps exceed trom 16 to 24 ounces of silver per ton, but the quantity operated upon is very large indeed, being about six thousand cargas (A carga is equal to 300Ibs) weekly : the grinding is partly carried on by steam power. There is but one reduction works in this locality, but it isthe largest of its kind in the world. The ores contain no gold. The district of Catorce, although now yiclding comparatively little ore, formerly gave very large quantities of chloride, bromide and iodide of silver. These were reduced to a great extent: by the “Caso process,” or in eopper pans. A large quautity of the ore from this district is also smelted in small blast furnaces. The ores contain no gold. — “In the district of Reyes the ores differ very muéh in composition, as may be seen from the following analyses :— First Second pilicas 2. dae. «sae ----50.000 ‘Silica. .24.00 Sulphide of iron.. 26521 Lead ..38.44 silver.. 150 Silver. oe He eLLD —' lead. 2076 ~~ Iron. een O00 P arsenic Fone eLUD occ 1517 a ZINC sos see 5.000 Sulphur .14.00 Sulphate ofivon..8 .258 lime.. 430 100.86 Oxide of manganese., 3.540 Carbonate of lime: -:. 4.160 "magnesia. .960 Moisture.<s.-09 08 6.800 99.995 Some of the antimony in the second analysis existed ag red sulphur. The first analysis may be taken as an average of the ores worked in this locality, although very frequently: antimony is also found in various proportions. By the Pa tio amalgamation not more than from one-half to three quarters of the silver can be obtuined from these ores, ant this only with a large loss of mercury, In examining vari ous samples from this district, we have found part of th silver to exist in the form of sélicate, which it is difficult separate except by smelting; and the ores in general are no sufficiently rich to admit of tbis process being adoptet where charcoal is so very expensive and scarce, Tu the district of Jaipa a very interesting mineral of silk ver has been found, which, according to R. Richter, has the following composition :— Silvers cece eee Copper. .\ceeea ees doo 20 CEE AOD 5 3.12 Mepagosnoqepescos Ac : 17g Sulphur.. see vvesntvedveteecten besides se) AOU 99.78 Affording the formula (34 Ag plus 14 Cu)S. It has a lead-iij gray colour, and is maflenite like ordinary silver-glane Cleavage monometrie, specific 6.877 to 6.890. Breithau has given it the name of Jalpaite, (American Journal off Science, 2 ser., vol. Xxvi. p. 358.) In many of the mineral districts of Mexico there.are thouet] sands of tons of low-class ores which would not pay the cost of amalgamation. Various plans and apparatus have been proposed from time to time for concentrating these by waslal. ing, but up to the present time we know of none which hi proved effective. Some of the machines have exhibit much skill on the part of the iaventors, and for many class= esof ores Ihave no doubt they might answer admirably. To concentrate these ores they would first have to be fine ground, because the sulphide of silver. is very intimate mixed with the gangue, and this operation is a: very. expe sive one in Mexico, having to be done by animal power Besides, in grinding, the sulphide being softer than the gai gue, becomes so fine that the portion which passes away i the water-used for washing contains in many instances much; and sometimes more, silver than the portion remaining ¥ behind. It may not be out of place just to remark here, that bee sides its wealth in silver, Mexico is much richer than is gen: erally supposed to be the case in other minerals. In ¢i present condition of the country these are of cour.e quife™ unavailable ; but they present the elements of great futuré prosperity when law and order are restored, and proper sect I rity given to induce the application of the necessary capi to make them available. Many of these ores are disting§ tive in their composition, and are little known in Europe. [To be continued.) Old Iron —The shipping of old iron from San Francisco ts to the East is becoming quite a business, and begins to attrae attention. Old iron is bought up in San Francisco at ten anv twelve dollars per ton. After going East and being wrough over, the same iron is reshipped to San Francisco and 4 for $80 and $110 pr ton. The Bulletin urges the establis! ment of a rolling mill in San Francisco to work np old iron and thereby stop such an unequal traffic as that of selling fo ten and twelve dollars per ton, and then buying it backa $80 and $110.

MINING AND SCIENTIFLE PRESSe [From Tze Loxpox “ Maing axD SMELTING MaGazine.”?] THE MEXICAN METHOD OF AMALGAMATION. BY JAMES NAPIER, JUN., F.C.S. Late Clicmist and Assayer to the Guanaxuato Mint, Mexico. INTRODUCTION, Before proceeding to describe in detail the Mexican method of amalgamating silver ores—which will principally apply to those which came under my own observation at Guasaxuato—I propose making a few introductory remarks on the history of the Pa'io amalgamation process, and on the composition of the ores charastzristic of some of the different districts. The ancients were well acquainted with the property which mercury has for-combining with gold and silver, and took advantagé of the fact for romoving gold from. old apparel by first burning them to ashes in an earthern pot and then amalgamating them. Humboldt also states that, before the discovery of Aierica,the Germans employed mereury to extract gold from auriferous sands as we!l as from iron and copper pyrites ; but we have ne knowledge of mereury having been employed for the purpose of extracting silver from its ores before the year 1557, when Bartolome Medina, a miner of Pachuca, in the neighborhood or Real del Monte, in Mexico, discovered the “Patio” method of amalgamation. It is very difficult to form any correct idea as to *how this wonderful process was invented, and whatit was that led to the discovery. It could not have been by chemical reasoning that Medina mixed the various ingredients—sulphate of copper, (magistral) salt and mereury— with the minerals of silver to extract the metal; and the discovery appears most extraordinary when we consider that the process requires weeks aud even months for its completion, so that a long time had to elapse before the result of ‘an experiment could be obtained. We can only suppose that Medina, being aware of the property which mercury has of combining with silver and forming amalgam—and also knowing that anhydrous sulphate of copper (obtained by calcining copper pyrites) when immersed in water gives out heat—conceived that if these were mixed with silver ore and common salt (which was thought to have a cleaning effect on the silver previ us to its combining with the mercury), that the heat caused by the sulphate of copper would favour the amalgamation. Although this process requires a long time for its completion, the operation of reduction commences almost at once, so that by taking out trials soon after the incorporation of the mass.it could be seen that the mercury was taking up silver ; and it would be easy to know, by burning at intervals a weighed portion of the amalgam, how much silver the whole qauntity of mercury added would contain, and when the process was completed. In 1586, 2 Peruvian miver of the name of Carlos Corso de Leca discovered what has been termed “el beneficio de hierro” (the reduction by irou.) This consisted in adding to the torta small pieces of metalic iron, the object of which -was to save mercury, which it would do by reducing the chloride of silver ; but Iam not aware of this process ever having been worked to any extent. The next improvement made was by Alonzo Barba, in "1590. It consisted in amalgamation in large copper pans, heated from below, and was called ‘‘el beneficio de caso y cocimienio.” In this process there was a great saving of mercury, but a large consumption of copper, as the chloride of silver was reduced at the expense of the copper pans; if answers very well for the native chlorides, but not for sulphides of siver. In 1784,this process was introduced into Europe by Baron de Born, au Austrian mining officer, and from it has sprang the barrel amalgamation of Frieberg, proposed, I believe, by Gellert. So that from the process first invented by Madina, in Mexieo, has sprung all others for amalgamating silver ores ; and although his original process has undergone many alterations, the principle still remains the same. SILVER ORES OF A FEW OF THE DISTRICTS OF MEXICO. I helieve that every known ore of silver has been met with in some one or otherof the numerous mineral districts of Mexico, but many districts have ores peculiar to themselves, and all ores will not yield their silver by the “patio” amalgamation. Perhaps the ores of Guanaxuaio yield their silver by the patio anunlgamation better than those of other districts,. from the fact of their containing but few foreign metals ; the silver being mostly found in the form of pure sulplides, in many instances’‘in carbonate of lime and quartz veins. The following shows an analysis of ore from the district of “La Luz,” in Guanaxuato :— Silver.. Tron 5.. . <ee eee 4,71 Carbonate of limes. .-=8.25 magnecia. 3.26 Sulphiay.i... gees 6.79 Copper. .....oa 55 99.60 This, however, is not to be considered hy any means as an average sample of ore from this district, for the average richness of the ores produced here will probably not exceed from 45 to 60 ounces of silver per ton. Nearly the whole of the ores of this locality contain gold in various proportions. To show what proportion the gold bears to the silver, we suhjoin the coinage of the mint of Guanaxuato for ten years, commencing at 1850. Coinage or Tur Guanaxvato Mint ror 10 years. Fay Te Ter Cent Year. Gold $ Silver $ Total $ of Gold 1850 709,472 7,801,300 8,510,772 8,336 1951 606,022 7,011,750 7,617,772 7.955 1852 746,956 7,625,650 8, 372,606 8.921 1853 723,078 6,235,922 6,969,000 10.375 1854 450,288 §,029,712 5,480,000 8.216 1855 555,200 4,698,800 5,254,000 10.567 1856 79,476 4,306,524 4,786,000 10.018 1857 570,700 4,747,300 5,318,000 10.731 1858 489,744 4,725,256 5,215,000 9.391 1859 438,8°0 5,046,120 5,485,000 8.001 The ores of Zacatecas frequently contain argentiferous blende, which makes them rather more difficult to work than those of Guannaxuato. Gold was almost unkuown in the mines of Zacatecas until 1856, when a vein was cut in the mine of the “Bote” containing large quantities of gold, which still continues to yield a considerable produce of that metal. Real del Monte produces ores of a very various nature, some containing considerable quantities of maganese ; as the following analysis of a sample by Mr. Rogers, from Santa Brigida vein in that district, will show :-— BGs dices ss eee evewes AP Gr Oro +++ -68.00 WAURITIN Gels; e apaisteleyel ele mies +) «)5 © SELES 6.00 Peroxide and sulphide of iron.... 7.50 JWAAED Donoso ocoupennccococgitibo oc 1.60

Sulphide 0188 GAG seam condbooonccs.n0 2.82 Peroxide of manganese....... 5.30 Sulplideof Zinc . sass 1 <> sel snee « 2.30 MUINIG «seeped < « c cieleletdiars + Wie nis/eieis 1.45 Dulphide Of Copper...5-..--..40 fap Saeco COC RGAE ooo Seo ape oog 25 Potash, antimony, tellurium, traces of soda, gold and loss... ier ouaue 2.38 100.00 My late lamented friend Mr. Edward Louckner, who has examined these and similar ores very carefully, states that the silver in many cases exists ag a manganate. The ore from the various mines of this locality differ very much in their nature and composition, and have consequently to be . reduced by different methods: some are reduced by patio, others by barrel amalgamation, and some are smelted, Some of the silver produced here contains sufficient gold to make its extraction a matter of importance. In the district of Angangueo the silver exists mostly combined with bl-nde and sulphide of lead, and is reduced bysmelting. The following analysis shows its composition : CATT Ot ei ong 52.09 SUDO Ut ee sci 2. .32.00 TOU Mele 2 cia/c/efe'= 70 ~ aie 13.44 ‘Antimony =. 22). << 2.40 DUVER ec ee ecu se eee ny 100.90 In Fresnillo the ores workeddono not perhaps exceed trom 16 to 24 ounces of silver per ton, but the quantity operated upon is very large indeed, being about six thousand cargas (A carga is equal to 300Ibs) weekly : the grinding is partly carried on by steam power. There is but one reduction works in this locality, but it isthe largest of its kind in the world. The ores contain no gold. The district of Catorce, although now yiclding comparatively little ore, formerly gave very large quantities of chloride, bromide and iodide of silver. These were reduced to a great extent: by the “Caso process,” or in eopper pans. A large quautity of the ore from this district is also smelted in small blast furnaces. The ores contain no gold. — “In the district of Reyes the ores differ very muéh in composition, as may be seen from the following analyses :— First Second pilicas 2. dae. «sae ----50.000 ‘Silica.. .24.00 Sulphide of iron... 26521 Lead ...38.44 silver... 150 Silver. oe He eLLD —' lead.. 2076 ~~ Iron. een O00 P arsenic Fone eLUD occ 1517 a ZINC sos see 5.000 Sulphur ..14.00 Sulphate ofivon...8 .258 lime... 430 100.86 Oxide of manganese., 3.540 Carbonate of lime: -:. 4.160 "magnesia.. .960 Moisture..<s.-09 08 6.800 99.995 Some of the antimony in the second analysis existed ag red sulphur. The first analysis may be taken as an average of the ores worked in this locality, although very frequently: antimony is also found in various proportions. By the Pa tio amalgamation not more than from one-half to three quarters of the silver can be obtuined from these ores, ant this only with a large loss of mercury, In examining vari ous samples from this district, we have found part of th silver to exist in the form of sélicate, which it is difficult separate except by smelting; and the ores in general are no sufficiently rich to admit of tbis process being adoptet where charcoal is so very expensive and scarce, Tu the district of Jaipa a very interesting mineral of silk ver has been found, which, according to R. Richter, has the following composition :— Silvers cece eee Copper. .\ceeea ees doo 20 CEE AOD 5 3.12 Mepagosnoqepescos Ac : 17g Sulphur... see vvesntvedveteecten besides se) AOU 99.78 Affording the formula (34 Ag plus 14 Cu)S. It has a lead-iij gray colour, and is maflenite like ordinary silver-glane Cleavage monometrie, specific 6.877 to 6.890. Breithau has given it the name of Jalpaite, (American Journal off Science, 2 ser., vol. Xxvi. p. 358.) In many of the mineral districts of Mexico there.are thouet] sands of tons of low-class ores which would not pay the cost of amalgamation. Various plans and apparatus have been proposed from time to time for concentrating these by waslal. ing, but up to the present time we know of none which hi proved effective. Some of the machines have exhibit much skill on the part of the iaventors, and for many class= esof ores Ihave no doubt they might answer admirably. To concentrate these ores they would first have to be fine ground, because the sulphide of silver. is very intimate mixed with the gangue, and this operation is a: very. expe sive one in Mexico, having to be done by animal power Besides, in grinding, the sulphide being softer than the gai gue, becomes so fine that the portion which passes away i the water-used for washing contains in many instances much; and sometimes more, silver than the portion remaining ¥ behind. It may not be out of place just to remark here, that bee sides its wealth in silver, Mexico is much richer than is gen: erally supposed to be the case in other minerals. In ¢i present condition of the country these are of cour.e quife™ unavailable ; but they present the elements of great futuré prosperity when law and order are restored, and proper sect I rity given to induce the application of the necessary capi to make them available. Many of these ores are disting§ tive in their composition, and are little known in Europe. [To be continued.) Old Iron —The shipping of old iron from San Francisco ts to the East is becoming quite a business, and begins to attrae attention. Old iron is bought up in San Francisco at ten anv twelve dollars per ton. After going East and being wrough over, the same iron is reshipped to San Francisco and 4 for $80 and $110 pr ton. The Bulletin urges the establis! ment of a rolling mill in San Francisco to work np old iron and thereby stop such an unequal traffic as that of selling fo ten and twelve dollars per ton, and then buying it backa $80 and $110.