Silver Ores Research Articles

Nuclear Fears and Monopolies

The story of uranium can be traced back to the bad luck of some Bohemian miners, looking for rich silver ore. But until the percentage of the uranium-235 isotope was enriched above its natural 0.7% occurrence to make the atomic bomb, the world cared little about the heaviest natural element. Here the politics of this enrichment are recalled, the agreements and disagreements between Great Britain and the USA, the efforts of France to catch up, and how monopolies in the gaseous diffusion process for enrichment arose, ending with URENCO and Eurodif, the former using the more efficient centrifuge process.

Nuclear Fears and Monopolies

Abstract The story of uranium can be traced back to the bad luck of some Bohemian miners, looking for rich silver ore. But until the percentage of the uranium-235 isotope was enriched above its natural 0.7% occurrence to make the atomic bomb, the world cared little about the heaviest natural element. Here the politics of this enrichment are recalled, the agreements and disagreements between Great Britain and the USA, the efforts of France to catch up, and how monopolies in the gaseous diffusion process for enrichment arose, ending with URENCO and Eurodif, the former using the more efficient centrifuge process.

Sulfurous Acid Pre-Leaching for Reprocessing Manganese Silver Tailings at Tonopah, Nevada

Manganese silver ores are well known to be refractory toward cyanidation. Roasting and sulfurous acid pre-leaching have been suggested for improving their amenability. This paper describes the development and implementation of the sulfurous acid pre-leach process for retreatment of manganese silver tailings at Tonopah, Nevada. The history of the material is summarized and the mineralogy is described. A brief review of an earlier application of sulfurous acid pre-leaching of a manganese silver ore is presented.

Improved tribenzylamine-silver bromide extraction/atomic-absorption spectrophotometric method for the determination of silver in ores, related materials and zinc process solutions

An improved tribenzylamine extraction/atomic-absorption method for the determination of silver in ores, related materials and zinc process solutions is described. The method, which involves the separation of silver by a single methyl isobutyl ketone extraction of the tribenzylamine-silver bromide ion-association complex from ~ 0.5–2 M sulphuric acid-0.14 M potassium bromide, is simpler and more rapid than a previous method based on a triple chloroform extraction of the complex. Silver is stripped with 12 M hydrochloric acid containing 1% thiourea as a complexing agent. Thiourea is destroyed with nitric and perchloric acids and silver is ultimately determined by atomic-absorption spectrophotometry in an air-acetylene flame, at 328.1 nm, in a 10% v v hydrochloric acid-1% v v diethylenetriamine medium. Cadmium and bismuth are partly co-extracted but do not interfere. Results obtained by this method are compared with those obtained previously by the tribenzylamine/chloroform extraction method and with those obtained by a direct acid-decomposition/atomic-absorption method.

The accurate determination of gold and silver in ores and concentrates by wet-chemical analysis of the lead assay button

Hydroquinone or formic acid can be used as reductant for the quantitative precipitation of gold in the lead perchlorate solution obtained after the lead assay button has been parted with perchloric acid. Silver chloride can be completely precipitated by dilution and overnight standing of the parting solution, thus both gold and silver can be isolated by filtration for the final measurement. The proposed lead-wet chemical method was successfully applied to ores, concentrates, dusts, etc.

Distribution of silver in massive sulfide ores

The distribution of silver in connection with the formation of massive sulfide ores is discussed. It is proposed: 1) The affinity between silver and galena-rich ores is only pronounced if antimony and/or bismuth are also present in significant amounts, and 2) The degree of correlation between silver and lead is partly a function of the Ag/Sb+Bi ratio in the ore and increasing with decrease in ratio at least up to Ag/Sb+Bi=1. Observations of correlated Cu/Ag ratios in complex ores indicate that some silver was solved in chalcopyrite at the time of deposition. This is often masked by the much higher silver contents associated with galena. The Bi/Sb ratio is expected to increase downwards stratigraphically in galena-rich ores, due to a larger solubility of silver-bismuth in galena as compared with silver-antimony, at a realistic deposition temperature (200–300 °C). However, such an effect will only rarely be seen, due to incomplete separation of the ore-constituents at the time of deposition, as well as to post-depositional changes.

Recovery of Gold and Silver from Ores by Hydrometallurgical Processing

Abstract The Bureau of Mines has played an important role in the revival of precious-metal mining in the Western United States. During the past 30 years, many techniques used by industry to recover gold and silver were pioneered and developed by the Bureau of Mines. In 1952, technology was developed to strip gold from granular activated carbon and allow the carbon to be reused. In 1969, the heap leaching concept was applied to low-grade gold and silver ores and mine wastes. Heap leaching in conjunction with carbon adsorption-desorption permits very low value material to be economically processed. In 1970, an oxidation treatment based on hypochlorite was developed to increase the recovery of gold from carbonaceous gold ores by cyanidation. In the early 1950's, attempts were made to employ carbon-in-pulp technology to recover gold from ores, but the fixed price of gold and increasing operational costs made cyanidation unprofitable. The Bureau of Mines and Homestake Mining Co. jointly operated a carbon-in-pu...

Reconnaissance and Economic Geology of Copper Mountain Metamorphic Complex, Owl Creek Mountains, Wyoming: ABSTRACT

The Copper Mountain metamorphic complex lies within a westerly trending belt of Precambrian exposures known as the Owl Creek Mountains uplift. This mountain range lies along the southern edge of the Big Horn basin, separating that basin from the Wind River basin to the south. Rocks of the metamorphic complex are exposed at Copper Mountain, at Wind River Canyon, and apparently continue several miles to the west on the Wind River Indian Reservation. The metamorphic complex at Copper Mountain is part of a larger complex known as the Owl Creek Mountains greenstone belt. Until more detailed mapping and petrographic studies can be completed, the Copper Mountain area is best referred to as a complex, even though it has some characteristics of a greenstone belt. The metamorphic complex is amphibolite-grade metamorphosed supracrustal rocks that have been migmatized along the north and south margins of the complex by the intrusion of leucogranitic stocks and batholiths. The regional trend of the metamorphic complex is N50° to 80°E, and regional foliation dips steeply to the south. The dominant structure along the southeastern margin of the belt is a synform. The supracrustal rocks are quartz, hornblende, plagioclase gneisses and schists, quartzites, para-amphibolites, pelitic schists, cordierite schists, iron formation, quartz-mica schists and gneisses, and intercalated orthoamphibolites. At least three episodes of Precambrian deformation have affected the supracrustals, and two have disturbed the granites. Prior to the intrusion of granite, the metamorphic complex experienced coaxial folding of the metasediments. Following the initial folding of the supracrustals, the Copper Mountain belt was intruded by leucogranite about 2.7 b.y. ago. This intrusive event is believed to be responsible for prograde metamorphism, as well as a second phase of deformation. Portions of the supracrustal belt were mineralized during the waning stages of the intrusive event. Some tungsten-bearing veins and calc-silicates were produced. Auriferous and cupriferous fracture-fill veins were formed, followed by emplacement of simple pegmatites. A final Precambrian deformation event was preceded by a weak thermal event expressed by retrogressive metamorphism and restricted metasomatic alteration. During this event, a second phase of pegmatitization was accompanied by hydrothermal solutions. During the Laramide orogeny, Copper Mountain was again modified by deformation. Laramide deformation produced complex gravity faults and keystone grabens. Uranium deposits were formed following major Laramide deformation. The genesis of these deposits is attributable to either the leaching of granites or the leaching of overlying tuffaceous sediments during the Tertiary. Production of metals and industrial minerals has been limited, although some gold, copper, silver, tungsten, beryl, feldspar, and lithium ore have been shipped from Copper Mountain. A large amount of uranium was produced from the Copper Mountain district in the 1950s. End_of_Article - Last_Page 1341------------

Determination of silver in ores, concentrates, zinc process solutions, copper metal and copper-base alloys by atomic-absorption spectrophotometry after separation by extraction of the tribenzylamine—silver bromide complex

A method for determining ∼0.1 μg/g or more of silver in ores and concentrates and ∼0.001 μg/ml or more of silver in zinc process solutions is described. Silver is separated from the matrix elements by chloroform extraction of the tribenzylamine—silver bromide ion-association complex from 0.08 M potassium bromide—2 M sulphuric acid and stripped with 9 M hydrobromic acid. This solution is evaporated to dryness and organic material is destroyed with nitric and perchloric acids. Silver is determined by atomic-absorption spectrophotometry in an air—acetylene flame, at 328.1 nm, in a 10% v/v hydrochloric acid—1% v/v diethylenetriamine medium. Cadmium, bismuth and molybdenum are partly co-extracted but do not interfere. The method is also applicable to copper metal and copper-base alloys. Results obtained by this method are compared with those obtained by a fire-assay/atomic-absorption method.

Eggonite (Kolbeckite, Sterrettite), ScPO4 · 2H2O

SynopsisThe curious history of the mineral eggonite is reviewed, and two new occurrences are described. The original specimens, for which Schrauf gave good morphological and optical data in 1879, with a tentative suggestion that it was a cadmium silicate, were fakes; the tiny crystals of the new mineral were glued on to hemimorphite specimens from Altenberg, Belgium. In 1929, Zimanyi edited and published observations by Krenner, who found the mineral on silver ores from Felsöbánya, Hungary, added to Schrauf's physical data, and identified it as an aluminium phosphate. It was not until 1959 that Mrose and Wappner showed that it is scandium phosphate, ScPO4 · 2H2O, and essentially identical with kolbeckite, described by Edelmann in 1926 as a phosphate and silicate of beryllium, aluminium, and calcium from Saxony, and with sterrettite, described by Larsen and Montgomery in 1940 as an aluminium phosphate from Fairfield, Utah.In 1980 the IMA Commission on New Minerals and Mineral Names, while accepting the identity of the three minerals and rejecting the name sterrettite, were almost equally divided over the names eggonite and kolbeckite, which are thus both acceptable; since eggonite has 47 years priority, we suggest that it should have preference.The available physical and chemical data on eggonite are summarized and added to, and two new occurrences, at Potash Sulfur Springs, Arkansas, and at Sakpur, Gujarat, India, are described.

A fire-assay and wet chemical method for the determination of palladium, platinum, gold, and silver in ores and concentrates

A method is presented for the determination of palladium, platinum, gold and silver in ores and concentrates by a fire-assay and wet chemical technique. After parting of the lead assay button with dilute nitric acid, and separation of the solution from the residue, the palladium and platinum in the solution are precipitated by the addition of stannous chloride, with tellurium as collector. The resulting precipitate is combined with the gold residue and dissolved in aqua regia, then the solution is analysed for palladium, platinum and gold by atomic-absorption spectrophotometry (AAS). Silver is determined in the original solution by AAS before the reduction step.

Women of Silver Plume

Silver Plume, Colorado, is a tiny former mining town located high in the Colorado Rockies (elevation 9,118 feet) about forty miles west of Denver. It was founded and built primarily by English miners and investors. In the mid-1860's, the first silver mines were opened, and in 1871, houses were being built on the valley floor. Eventually it supported two churches, a post office, theater, jail, schoolhouse, several general stores, saloons, and boardinghouses, with a population estimated at 2,000 people in 1875. The town was incorporated in 1880, reached its peak in the early 1890's and proved to be of the richest silver mining districts in Colorado, eventually producing over $120 million in silver ore. Mining continued profitably until the early 1900's, but dwindled to a standstill by the mid-1950's. Silver Plume now exists in a period of transition. It is experiencing the increasing pressures of tourism and commercial growth. A resident says, Since I've been here, I've seen the closing of the school, the building of an interstate which wiped out two complete business enterprises, a row of houses, the old depot, and a grazing area, and I've seen the closing of four mines. Now we have a train which is run strictly for tourists. Is this supposed to be good? Is this progress? There are not many old people left in town and those still here look back on the times when it was all one big happy family and you could talk across the back fence, and there was no crime, and you felt that everyone really cared. The town is growing again and perhaps its only constant is change. Through these photographs and statements, I have let the women of the town speak for themselves. Their jobs are as varied as their personalities. They do mining, bartending, homemaking, paper hanging, silversmithing, tending to the streets and waterworks, modeling, poetry and songwriting, mothering, operating gas stations and stores, teaching, selling real estate. They are strong, interesting, and a vital part of the town of Silver Plume. v. ..y...

ON THE FORM AND THE MINERALIZATIONS OF COPPER ORES IN THE ORO DENORO MINE, BRITISH COLUMBIA, CANADA

The Oro Denoro Copper mine is one of the contact ore deposits scattered in Boundary District, British Columbia, Canada. Many investigations such as geological surveys, geophysical prospectings, prospectings by drilling and underground prospectings were carried out at this mine and other mines around it from 1956 to 1968. The geology of the Oro Denoro mine consists of sedimentary rock and various kinds of intrusive igneous rocks. The sedimentary rock belongs to the Brooklyn Formation of the Palaeozoic era which consists principally of limestone and calcareous rock containing small amounts of tuff, pyroclastics, argillite and sharpstone. These sedimentary rocks have been widely given the folding and faulting. They were given the contact metasomatism by the intrusion of the granodiorite batholith of the Mesozoic era called Lion Creek Intrusive and Emma Intrusive. The ore deposits are mainly grown around the skarn zone and granitic rocks. The characteristics of the ore deposits are as follows: (1) The metallic mineral in the copper ore consists largely of chalcopyrite containing a very small amounts of bornite and ores of gold and silver. The metallic gangue minerals are pyrite, magnetite, hematite, pyrrhotite and other iron ores. (2) The zone rich in copper is divided into two types. (a) The zone rich in copper is made up by various types of veins or banded ore bodies, the mineral deposition of which is controlled by many fissures in the sakrn zone. As a result the continuity of the zone rich in copper is poor and the copper ore is produced as wedge or rib. (b) The zone rich in copper shows bedded ore bodies, the mineral deposition of which is controlled by fissures in layered limestone, fracture zones or permeable skarn. As a result the copper content in the ore bodies is low, although they are big. (3) In general the mineralization is active in z ones where the skarnization has been advanced. The skarn accompanied by chalocopyrite is discontinuous, of irregular shape and distributed mainly in the central zone of the zone of high grade skarn. The grade of the skarnization is decreased concentrically on the horizontal cross section from its center to the outside. (4) The kinds of the skam minerals are nearly the same every place, which consist largely of garnet such as andradite and grossularite rich in calcium found in contact metasomatic deposits in Japan.

The Milluachaqui epithermal silver district of northern Peru

The mines in the Milluachaqui district, located near Salpo in the northern part of Peru, show a vertically zoned, epithermal silver-gold mineralization. Colonial production was obtained from oxidized, high-grade ores, consisting mostly of native silver and cerargyrite. More modern development exposed, from the top of ore shoots to their base, the "bonanza" ores (the pyrargyrite-polybasite-acanthite zone), silver-copper ores (the tetrahedrite zone), silver-lead ores (the galena-sphalerite zone), and the basal zone ores (the sphalerite zone). The ratio of gold to silver in the "bonanza" ores was about 1 to 100, by weight. Interpretation of mineralogical textures and the composition of minerals in the sulfide zone suggests that supergene movement and enrichment of silver at Milluachaqui was not a significant factor. Silver tended to be fixed in place during weathering as the chloride and native mineral. The "bonanza" ores are interpreted to be hypogene sulfide accumulations. These findings contrast to hypotheses proposed for some epithermal districts in the U.S. which assume supergene activity to have been significant in the accumulation of high grade, near-surface silver ores.

An abbreviated fire-assay atomic-absorption method for the determination of gold and silver in ores and concentrates

A simplified scheme, combining aspects of the classical fire-assay with an atomic-absorption finish, is presented for the determination of gold and silver in ores and concentrates. The lead assay button is scorified to approximately 2 g and then parted in nitric acid. The filtrate is analysed by AAS for silver; the residue is dissolved in aqua regia and subsequently analysed for gold by AAS. The precision and accuracy of the method have been established by application to four diverse certified reference materials. The proposed method eliminates the need for such time-consuming steps as inquartation, multiple scorifications, and cupellation.

Some Mineralogical Characteristics of the Silver Deposits in the Guanajuato Mining District, Mexico

The silver ores in the Guanajuato mining district in Mexico consist of disseminated silver sulfides, selenides, and electrum in quartz-calcite veins and occur in three different ore types. The mineralogical and chemical characteristics of the ore types were defined and the chemical compositions of some of the minerals were determined. It was found that the different ore types contain approximately the same minerals but in different proportions and specific minerals occurring in different ore types contain the same minor elements but in different quantities.

O 18 /O 16 evidence for meteoric-hydrothermal alteration and ore deposition in the Tonopah, Comstock Lode, and Goldfield mining districts, Nevada

Oxygen isotope analyses were obtained for 50 whole-rock samples, 26 vein quartz samples, 4 calcites, and 1 adularia from the volcanic rocks, intrusives, and hydrothermal veins at Tonopah, Goldfield, and the Comstock Lode. At Tonopah, the delta O 18 values are as follows: Mizpah trachyte (-5.9 to +3.3); West End rhyolite (--4.7 to +1.5); Sandgrass andesite (--6.0); main-stage vein quartz (--5.1 to --1.8); late, euhedral quartz crystals (--3.2 to +0.7). The delta D values of 5 of these rocks vary from --135 to --152. These materials are thus depleted in O 18 by about 5 to 15 per mil and in D/H by about 60 to 70 per mil, relative to values in normal igneous rocks. The postmineralization Oddie rhyolite and Fraction volcanic breccia, however, have much higher delta O 18 values (+2.5 to +9.5). The hydrothermal alteration and ore deposition therefore must have been produced by heated meteoric ground waters (delta O 18 [asymp] --13, delta D [asymp] --100) that had undergone very little or no O 18 enrichment as a result of exchange or addition of magmatic water. Various models suggest that this involved very high water/rock ratios (>2) and occurred at about 250 degrees -300 degrees C. Although the delta O 18 of quartz is higher (+1.5 to +3.0), the range of whole-rock delta O 18 values at the Comstock Lode is similar to that at Tonopah: Alta andesite (--4.1 to +4.7); Davidson diorite stock (--2.6 to --0.8). At Goldfield, somewhat higher whole-rock delta O 18 values are observed: altered volcanic rocks (+1.7 to +5.8); ore zones (--3.8 to +3.8). These data also indicate a dominant meteoric ground-water component in the hydrothermal fluids, but they suggest smaller water/rock ratios at Comstock and lower temperatures of alteration at Goldfield. It is concluded that most epithermal gold and silver ore bodies in highly faulted piles of altered volcanic rocks probably were deposited by meteoric-hydrothermal solutions heated and set into convective circulation by interaction with epizonal igneous intrusions.

The determination of silver in ores by anodic stripping voltammetry

Stripping voltammetry at a rotating glassy carbon electrode is proposed for the determination of silver in ores. The ores or concentrates are dissolved in suitable acid mixtures, and silver is separated either by extraction with dithizone in carbon tetrachloride, or by adsorption on silica from ammoniacal buffered solution and subsequent elution with 0.1 M nitric acid. The results obtained with stationary and rotating glassy carbon electrodes are discussed. Stripping voltammetry and fire assay give results in reasonably good agreement.

Radioactive Silver in East European Silver Bars

THE discovery of slightly radioactive silver in the form of the isotopes 108mAg and 110mAg in East European silver bars1 is of considerable interest, because so far as is now known these short-lived radioactive isotopes have not been observed in natural materials2. Lindner et al.1 have given four possible explanations for the presence of the radioactive isotopes, one of which is that the silver ore was mined by an underground nuclear explosion. An alternative natural explanation for the phenomenon seems more probable.

A method for the determination of silver in ores and mineral products by atomic-absorption spectroscopy

An atomic-absorption spectroscopic method for the determination of silver in some ores and mineral products is reported. The effects of sorption of silver on the container walls, cleanliness of equipment, stability of standards and sample solutions, interference from silicate ions and background absorption have been studied.The sample is treated with mixed acids (including hydrofluoric) and evaporated to dryness; the acid extract of the residue is then made strongly ammoniacal and the solution nebulised. Recoveries are, on average, about 10 per cent. higher than those obtained by using fire assay. Silver values obtained by the proposed procedure are almost quantitative for sulphide ores, but with other ores they are about 3 per cent. low, unless the final residue is re-examined.