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By G. W. Poling, G. W. Hawthorn

"""Unassayable gold and platinum group metals"" have come into vogue in the 70sand 80s in certain jurisdictions as a means of perpetrating fraud. Usual arguments are that a particular ore is not amenable to ""conventional fire assaying"". Explanations for unassayable gold usually revolve around: evaporation of micron-size gold; vaporization of organic gold complexes; volatization of gold halides; alloying of gold with PGM's which prevents fusion or alloying which prevents collection .This paper reviews several of the myths and truths of gold and PGM assaying with the knowledge that not a single mine operatesin thefree world producing gold from unassayable ore.INTRODUCTIONAccurate analyses of exploration data and estimation of ore reserves are two of the most important functions of professional geologists and engineers in mine development. The problems encountered become particularly acute when dealing with precious metal values where very low grade deposits (in the range of 0.0 I Troy oz per ton or - 0.2 ppm (g/t) by weight) sometimes are economic or constitute ""ore"". To emphasize this ""scarcity effect"", a gold assay of 0.4 g/t (0.01 T oz/st) would result from the presence of a single 420 J.tm (35 mesh) gold flake (which weighs I milligram) in a 5 kilogram siliceous sample.The current high gold price and the prospects of high profit margins awaiting exploitation of even very low grade gold deposits, has spawned a sizeable group of incompetent or fraudulent gold assayers. These ""assayers"" will often report significant precious metal values where no such values occur. Failures of legitimate assay labs to confirm these ""significant"" assays are often attributed, by the charlatan, to their capability of detecting ""unassayable gold"" while the check assayer cannot. Geologists and engineers lacking detailed knowledge of sampling and assaying techniques are often hard-pressed to convince a gold-fever aroused company executive or investor-client to abandon a property on which attention-grabbling values have been reported, often by more than one laboratory. Professionals engaged in such evaluations must acquire an understanding of contemporary precious metal sampling and assaying techniques . Only then can they determine whether misrepresentation of values have been perpetrated"

Jan 1, 1989

By Michael M. Kimberley

Gold is sufficiently valuable that concentrations as small as 1 p.p.m. may support low-cost mining. Mindful of this, Sunoco Energy Development Company (Sunedco) obtained fire-assay analyses on some sulfide-rich sandstone encountered during routine drilling. Initial fire-assay values from independent laboratories indicated some significant gold values and independent analysis by atomic-absorption spectroscopy also indicated detectable gold at economically interesting concentrations. Sunoco geologists realized the potential for spurious results inherent in both fire assaying and atomic-absorption spectroscopy. Fire assaying that relies on gold measurement by weight requires perfect separation of gold from all other elements, Imperfect separation may artificially enhance apparent gold concentrations. Atomic-absorption-spectroscopy (AAS) measurements are potentially subject to interferences from other elements. For example, Beamish and Van Loon (1977, p.4) report AAS measurements of 4 p.p.m. Au to be characteristic of completely barren soil samples when samples are prepared by standard dissolution in HC1 to form solutions of about 10,000 p.p.m. total cations (mostly Na, Ca, Mg, Al, and Fe) .

Jan 1, 1981

By J. Y. Foley, K. Eden, A. E. Grosz, C. J. Giles, J. E. Grosz

"Portions of the Icy Cape placer Au district have been described and exploited since the early 1900s. Industrial studies of Au-bearing garnetrich intervals established a 3.5 million troy ounce resource in the western half of the district. This estimate is not compliant with CIM and SME definition standards for Mineral Resources and Mineral Reserves. We note high variability in the textures of sediments and their heavy mineral (HM) content and composition in the district, probably as a function of the depositional environment. Sediments are medium- to fine-grained sands with a valuable HM assemblage that averages 26.0% in a range of 1.1– 72.6%. Valuable heavy minerals (VHMs) garnet, magnetite, ilmenite, rutile, and zircon, but excluding Au, average 7.9% in a range of 1.0–37.6% of the HM assemblage. Trace quantities of uraninite, thorite, monazite, xenotime, and others are noted. Garnets have an average Y content of 726 ppm with a range of 0–2150 ppm. Energy-dispersive X-ray fluorescence confirms compositions commensurate with Ca, Al, and Mg silicates. We provide empirical analytical data and note high variability in the textures, HM content, and compositions as a probable function of depositional environment. Icy Cape District land and resources are owned by the Alaska Mental Health Trust Authority and managed by the Trust Land Office (TLO). IntroductionThe Icy Cape Heavy Minerals (HM) District in Alaska subtends more than 200 km2 fronting the Pacific Ocean and backing to the foot of the Robinson Mountains at about 1700 m above sea level. We classify the district into geomorphic provinces; the eastern region as deltaic (Figure 1) and the western region as coastal plain (Figure 2), based on geomorphologic expressions. The coastal plain is entirely built up of unconsolidated outwash sediments and ancient beach sand deposits."

Jan 1, 2017

By J. Y. Foley, K. Eden, A. E. Grosz, C. J. Giles, J. E. Grosz

"Portions of the Icy Cape placer Au district have been described and exploited since the early 1900s. Industrial studies of Au-bearing garnetrich intervals established a 3.5 million troy ounce resource in the western half of the district. This estimate is not compliant with CIM and SME definition standards for Mineral Resources and Mineral Reserves. We note high variability in the textures of sediments and their heavy mineral (HM) content and composition in the district, probably as a function of the depositional environment. Sediments are medium- to fine-grained sands with a valuable HM assemblage that averages 26.0% in a range of 1.1– 72.6%. Valuable heavy minerals (VHMs) garnet, magnetite, ilmenite, rutile, and zircon, but excluding Au, average 7.9% in a range of 1.0–37.6% of the HM assemblage. Trace quantities of uraninite, thorite, monazite, xenotime, and others are noted. Garnets have an average Y content of 726 ppm with a range of 0–2150 ppm. Energy-dispersive X-ray fluorescence confirms compositions commensurate with Ca, Al, and Mg silicates. We provide empirical analytical data and note high variability in the textures, HM content, and compositions as a probable function of depositional environment. Icy Cape District land and resources are owned by the Alaska Mental Health Trust Authority and managed by the Trust Land Office (TLO). IntroductionThe Icy Cape Heavy Minerals (HM) District in Alaska subtends more than 200 km2 fronting the Pacific Ocean and backing to the foot of the Robinson Mountains at about 1700 m above sea level. We classify the district into geomorphic provinces; the eastern region as deltaic (Figure 1) and the western region as coastal plain (Figure 2), based on geomorphologic expressions. The coastal plain is entirely built up of unconsolidated outwash sediments and ancient beach sand deposits."

Jan 1, 2017

By Butler I. K, Nicholson P. M

There are four main types of base metal and gold mineralisation recognised in the central Pine Creek Geosyncline. These are stratiform, polymetallic veins, stockwork/concordant gold-quartz veins and unconformity related uranium-gold-platinoid mineralisation. The stratigraphy of the central Palaeoproterozoic Pine Creek Geosyncline has been simplified into three groups comprising the Batchelor, Frances Creek and Finniss River Groups in ascending order. Stratiform mineralisation occurs within the Frances Creek Group. The earliest mineralisation is found adjacent to circular faults ringing basement highs. Higher in the stratigraphy, stratiform mineralisation is often associated with zones of high compression in the vicinity of basement highs. A synsedimentary-diagenetic origin for stratiform mineralisation is proposed. Polymetallic vein mineralisation occurs within the Frances Creek and Finniss River Groups. Its composition changes systematically through the stratigraphy similar to the stratiform mineralisation. The mineralisation is structurally controlled and usually occurs in the vicinity of basement highs. Stockwork-concordant gold-quartz vein mineralisation is hosted by the upper Frances Creek and Finniss River Groups. It occurs within compressional zones and along the Pine Creek Structure corridor around, above and particularly between basement highs. Mineable reserves occur in thick continuous semi concordant quartz-sulphide veins and/or stockworks. Unconformity related uranium-gold-platinoid mineralisation shows a close spatial relationship with the Palaeoproterozoic/Mesoproterozoic unconformity. The mineralisation is localised by structures formed during Mesoproterozoic deposition and is commonly adjacent to Archaean basement or its remobilised equivalents. The type of mineralisation (stratifom/polymetallic vein) is a reflection of local stress regimes, structure and physio-chemical conditions. An initial phase of stratiform mineralisation is postulated to have occurred with the first significant marine transgression in a tensional regime. A second phase occurred later during a compressive regime. "Ihermochemical sulphate reduction of mineralising fluids by hydrocarbons is invoked as the precipitation mechanism for the polymetallic vein type of mineralisation. Hydrocarbon generation is postulated to have occurred within the Frances Creek Group, in many places contemporaneously with the movement of mineralising fluids and basin compression. Polymetallic veins formed from the interaction of mineralising fluids and hydrocarbons which were trapped in suitable structures. An abundant, continuing supply of hydrocarbons was necessary to form significant deposits. Where these conditions were not net, the mineralising fluids largely continued their ascent to the near surface environment to form stratiform deposits. The stockwork/concordant gold-quartz vein mineralisation is a later event and occurred during the relaxation of compressional defonnation after deposition of the 1-inniss River Group.

Jan 1, 1994

The first mining in Western Australia probably commenced some 40 000 years ago when Aborigines arrived and began quarrying stone for tools and weapons, and ochre for decoration. The earliest documented mining by European settlers took place in 1850 on a small lead vein in the bed of the Murchison River, reported by the explorer A C Gregory. However, it was the discovery of gold in the Kimberley region in 1885 that first drew wider attention to the State's mineral potential.

Jan 1, 1992

By W. J. Millard

VAGUE rumors and stories have been heard, from time to time, about the diamond and gold deposits of southern Venezuela. It is perhaps appropriate, at this time of revived interest in gold mining, to publish a few facts in regard to this country, which has been undergoing exploration since the fifteenth century. Gold and diamonds are found principally in the State of Bolivar which lies in southeastern Venezuela and is bounded by British Guiana on the east and Brazil on the south (see Fig. 1). The famous Mt. Roraima is situated at a point where these three countries meet in a common point (see Fig. 2). Some gold is also found in the southern part of the territory of Amacuro. Good oil prospects exist in the northern part of this same territory. Diamonds are found on the Caroni river from Rio Paragua to the village of Guri. Another small district is on the headwaters of the Cuyuni river. Quartz veins containing gold are chiefly exploited in

Jan 1, 1931

By William F. Butler, Mo-Hung Che

DEVELOPMENT OF MONEY AND MONEY STANDARDS This chapter is concerned with the rise, and then the decline and fall, of gold and silver as monetary metals. As a first step in tracing the history of this process, it is necessary to consider the nature of money, and the manner in which different forms of money have developed over the centuries. The origins of money go back into deepest antiquity. Once men ceased to be pure nomads and entered into even a rudimentary form of society such as clans or tribes, money had to be invented The first step was barter as farmers or hunters swapped their surplus products for things produced by artisans such as shoes, clothing, and simple tools. But such barter trading is inconvenient even in primative societies It is difficult to match up buyer and seller at any point in time There are problems in arriving at viable and acceptable terms of exchange. The accumulation of savings-wealth-is complicated. No one can be sure that a pile of furs, or wheat, or certainly fish or game can be used in the future to trade for other goods or services. So even prehistoric man saw the need for money. There was a need first for something to serve as a medium of exchange This was an essential first step in the process of specialization-or the division of labor. A farmer, a hunter, or a shoemaker could only devote his full efforts to his trade if he could be sure that he could exchange his surplus production for the other things he needed for existence. This required a medium of exchange-a form of money which would be broadly acceptable. Money was needed for two other reasons Some system of market prices was essential to facilitate the exchange of goods and services. This required some form of common denominator-some standard of value-to govern the exchange process. And there was also need for something to serve as a store of value, a place to put any excess production (savings) with the assurance that it can be used in the future to acquire a general range of goods and services. As a result, money, in one form or another, developed at a very early state in civilization. Yet the centuries have been marked by a search for a form of money which will possess in full measure all of the attributes in money-a reliable and universally acceptable medium of exchange, standard of value, and store of value. -A wide variety of things have been used as money at one time or another: shells, beads, stones, feather, metals, and even the teeth of sharks and dogs. Some of these things were obviously of little or no practical value. They were used because people had confidence in their continued acceptance as a medium of exchange. As the world evolved and as trading ex-

Jan 1, 1976

By L. C. Stone, J. C. Parr, T. N. Anderson, D. Metcalf

An increase in the importance of low-grade materials as sources of gold and silver has led to the need for improved analytical methods on leach solutions, ores and various effluents, residues, and in-process streams. These are required by plant operators as guides to process control and for accounting pldrposes. Atomic absorption spectrophotometry (AAS) and AAS preceded by pre- concentration have been applied successfully to resolve many such problems. However, AAS is no panacea and imprecision or loss of accuracy can result if adequate precautions are not taken to prevent losses and eliminate interferences. The recent methods are discussed together with methods for overcoming difficulties. Comparisons with more classical analytical techniques are also given.

Jan 1, 1981

By T. N. Andersen

The history of gold and silver analyses shows an interesting duality. On one hand, classical chemical and instrumental methods have evolved to meet changing needs, but on the other hand, the age-old and somewhat empirical fire assay has remained a popular tool. Inasmuch as gold and silver generally have been present in ores at low concentra¬tions, methods have been challenged by a need for sensitivity and selectivity coupled with reasonable assay time. A progressive increase in the importance of low grade materials as ore sources has led to the need for improved methods. Assays of these materials are required for process control and accounting in operating plants as well as for guiding research and development activities. The analytical response to these needs is evidenced by numerous reviews published through 1977-¬e.g., cf Kolthoff and Elving (1966), Beamish and Van Loon (1966, 1972, and 1977), Young (1971) , Mallett (1970), and Sen Gupta (1973). In this paper we present a brief sketch of the history and status of various gold and silver methods. A more detailed summary of atomic absorption spectroscopy (AAS) is Given, as this method has gained in popularity more than other assay methods. AAS methods currently in use are summarized and discussed briefly. This paper is not meant to be a detailed review, as are the above mentioned publications. Rather, we borrow from those works and more recent papers to report trends in gold and silver analyses (particularly in AAS). Also, we discuss some selected poten¬tial problems, and problems that have been experienced by this laboratory.

Jan 1, 1981

By D. Potter

In 1990, Freeport Exploration began regional reconnaissance exploration programs in Irian Jaya, the easternmost province of the republic of Indonesia (Fig. 1). Irian Jaya occupies the western half of the island of New Guinea. Freeport was awarded an initial contract of work that totaled 2.6 million hm2 (6.4 million acres). The company was subsequently awarded additional concessions that added 1 million hm2 (2.5 million acres). The concessions require work commitments and periodic relinquishments. Due to these relinquishments, Freeport’s current land position totals 1.9 million hm2 (4.7 million acres). Freeport began the exploration program to locate additional Grasberg deposits, the largest deposit in the Ertsberg district. But the company recognized that other types of deposits could be present in the largely unexplored area of Irian Jaya.

Jan 1, 1999

By M. W. BERNEWITZ

AUSTRALIANS and New Zealanders, whose countries have respectively yielded gold to the value of £666,000,000 and £96,000,000, are taking full advantage of the current high prices for that metal. There is a marked activity in ordinary prospecting, geophysical exploration, further development of working mines and reopening of old properties, formation of new companies, installation of new equipment and processes, and expansion of operations generally. Australian gold production last year was approximately double the quantity of 1929 and its value three times as great, 1929 being the low of recent years. The 1933 production was about 821,000 oz. From New Zealand, 165,000 oz. was exported last year. Papua and New Guinea contributed slightly over 100,000 oz. What the future price of gold will be nobody knows, but, even if it returns to the former level, Australian producers are almost sure of 110 shillings an ounce until 1940 through the Commonwealth Government's Gold Bounty Act, at present temporarily and necessarily suspended from operation.

Jan 1, 1934

By Patrick R. Taylor

United States Antimony Corporation, at its Yankee Fork property in central Idaho, is currently using a combination of flotation, gravity-amalgamation, and concentrate cyanide leaching, silver sulfide precipitation, and activated charcoal loading to recover both silver and gold. Tine processes of flotation, milling, gravity concentration, amalgamation, concentrate leaching, sulfide precipitation and gold recovery via charcoal are discussed. The flow sheet illustrates the use of cyanidation as an alternative to shipment to a smelter.

Jan 1, 1984

Primary sulphidic gold ores in the Archean provinces of Western Australia can be broadly sub-divided into pyritic, pyrite-telluride, arsenical and antimonial types. Pyritic ores contain only native gold, and are essentially not refractory. Arsenical ores almost always carry some invisible gold, and may vary from mildly to highly refractory. Pyrite-telluride ores contain gold-bearing tellurides, and are refractory to varying degrees. Antimonial ores usually contain aurostibite, and may be very difficult to process. A classification scheme for metallurgical processing, based on mineralogy, is proposed for the ores, and implications for processing are discussed.

Jan 1, 1995

By T J. Sprott, Associates

A number of people have expressed concern, understandably, that if mining operations take place in the Coromandel, the flows of mineralised ground water which exist will be intercepted. This water in many cases contains toxic metals including mercury, arsenic and lead and it is thought that if this water is allowed to enter streams or the waters of the Hauraki Gulf, it could endanger natural marine life and possibly established fisheries. This paper seeks to explain in simple terms the geology and the process of deposition of the various mineral deposits in the ground, the chemistry of the reactions between these minerals and the rain water falling on the ground, the hydrology and behaviour of this mineralised groundwater as it moves through the ground until it eventually enters the sea.

Jan 1, 1981

By James R. Finlay

SOMETIMES the American Institute of Mining and Metallurgical Engineers appears to be a strictly technical society, and if so my paper should deal with the technical operations of finding and producing gold. But I have not been engaged in practical gold mining since 1910. What I have been doing mainly for the last 25 years is to try to figure out what the income of a mine-gold, or any other-would be worth to an investor. So I have been in contact with gold mining, in one way or another, for some 42 years. I say that with a purpose. In that time the industry has been through one of its cycles. The value of gold mines is very dif¬ferent at different points in one of these cycles. For this reason the cycle of gold mining is a highly practical study. The cycle of gold is a more or less rhythmical change in its value or purchasing power measured in the grand average of other commodities, which is the same thing as its price. Taking the price of gold in 1897 as a stand¬ard, a dollar at that time declined to 55c. in 1913, to 26.8c. in 1920, and since then it has risen to 47.4c. in 1930 and to about 64c. in 1932. It is worth about 21/ times as much now as it was in 1920, but less than two¬thirds as much as in 1897. When this change is applied to the value of a gold mine still greater differences are evident. The cost of producing gold is of course measured in labor and other commodities, and as that cost goes down the margin of profit measured in the gold itself increases. Thus a mine which might make only 10 per cent profit in 1920 on its gross output may easily make 25 per cent now. The stockholder gets 2 ½ times more gold that is worth 2 1/2 times as much in purchasing power, therefore the real value of his holding has risen by the one factor multiplied by the other, giving him 61/4 times as much goods or services as he had in 1920.

Jan 1, 1933

By Paul Gilmour

"The principal role of the geologist is to recognize the existence of phenomena before trying to explain them" - B.M. Keilau, 1825; A. Holmes, 1965 Some important groups of mineral deposits in the layered rocks of orogenic belts or greenstone belts occur in horizons characterized by the presence of exceptional amounts of silica, iron and carbon, with more or less significant amounts of manganese. Generally, the rocks involved are well banded. In practice, these five physical features - four compositional and one geometric - are found with many lithological guises. Iron formation, in the full, modern sense of the term (James, 1954), quartzite, ferruginous quartzite, chert, jasper, "tetsusekiei" (Horikoshi, 1969), tuffaceous jasper ("purple porphyry" - Anderson and Creasey, 1958, p. 36), ferruginous or graphitic shale, argillite, slate or schist, and hematitic tuff are but a few of the more familiar of the names that have been assigned to these rocks. Widely acknowledged and well-documented examples of metallic deposits found in such sediments include concentrations of iron and manganese and stratabound, polymetallic, massive pyritic sulfides. Less familiar examples include occurrences of asbestos (Miles, 1953; and Coetzee, et al., 1976), antimony (Coetzee, 1976), and perhaps stratabound deposits of Au-Cu-U-W-etc., such as Aitik in Sweden (Mining Magazine, 1975; and Nilsson, 1979) and Olympic Dam in South Australia (Roberts and Hudson, 1983). The case of gold is intriguing. An association between gold and iron formation has been identified at several famous deposits and districts, such as Yellowknife, N.W.T. (Morton, 1979), Homestake, S. Dak. (Sawkins and Rye, 1974), Vubachikwe, Zimbabwe (Fripp, 1976) and the Barberton district, R.S.A. (Hammerbeck, 1976). Yet a critical reading reveals the existence of many other hitherto unsuspected examples. The purpose of this note is to draw attention to that omission and the apparent explanation for it. It is not hard to detect the two most probable reasons for the discrepancy between reality and the record.Most occurrences of gold are associated, not with the familiar banded iron formation or interbedded magnetite and chert (technically, the magnetite-banded variety of the oxide facies), but with the enigmatic carbonate, sulfide and silicate facies of iron formation and/or with rocks evidently related to iron formation. All too commonly, the unfamiliar facies of iron formation have been identified by field and mine geologists and not a few researchers as products of regional metamorphism and hydrothermal alteration, as mafic igneous rocks, or as conventional sediments, ie., without regard to their intrinsically ferruginous nature. The justification for these two complementary assertions is largely to be found in the recognition of a characteristic suite of metals and minerals in gold deposits known to be associated with iron formations. Although, from a geological standpoint, a lithological association is more important than a mineralogical assemblage, the latter is the more likely of the two to be diagnostic. This arises from the different natures of mineral and rock classifications, The identification of a mineral or an element is a matter of fact. Owing to the genetic component inseparable from petrographic nomenclature, viz., "igneous": a rock (believed to have been) derived from a melt, the identification of rocks depends on inferences or conclusions about their mode of formation - conclusions that are commonly debatable and, all too often, involve subjective judgements. This is especially prone to be true, if - as at many of the gold occurrences in question - the host rocks have been metamorphosed and/or "altered". In the notes that follow greater weight has accordingly been assigned to elemental and mineralogical than to host rock composition. In other words, if, in a given gold occurrence, the suite of metals and minerals present conforms to the standards of the subject class, whereas the names assigned to host rocks do not, the latter will be viewed as suspect.

Jan 1, 1985

By Stephen B. Doppler

INTRODUCTION Following the world stock market debacle in October 1987, it would have been foolhardy to expect that securing equity funding in 1988 would be easy. Indeed, major equity financing's for gold mining companies have until recently been few and far between in the weeks and months following Black Monday. As a result, gold bullion loans have taken on an increasingly important role among producing firms in the industry. During 1988, the role of bullion loans has become increasingly complex and controversial. Some observers herald the emergence of a new breed of bullion loans - such as the 1,000,000 ounce loan to Newmont Mining, and the 400,000+ ounce facilities drawn down by Bond International Gold and Placer Pacific - as both increasing the public's awareness of the technique, and representing the dawn of a new age of gold financing. But are these recent loan facilities significantly different than those issued worldwide during the early to mid 19801s? Similarly, observers have voiced concerns regarding the role that gold loans play in the world's bullion markets, specifically in relation to their impact on prices. Have the new generation of mega-loans depressed current and future prices? Has the current surge of bullion loans irrevocably changed the nature of the gold market? Is there an upper limit on the number and size of gold loans?

Jan 1, 1988

By Elma van der Lingen

Gold is considered the most inert of all metallic elements, but the metal can show catalytic activity when prepared by specific techniques. Preparation techniques being used to prepare gold catalysts systems mainly involve precipitation methods incorporating gold compounds or complexes. This paper introduces a totally different method for the preparation of gold-based heterogeneous catalysts that can be used for oxidation and reduction reactions, as well as electrocatalysts. The method involves alloying of gold with a less noble metal, such as aluminium, to form a gold-containing intermetallic precursor. AuAl2 was produced by melting gold and aluminium together in a vacuum arc furnace under a protective atmosphere. The aluminium is then dissolved from the AuAl2 precursor by means of NaOH to produce a highly porous gold structure. The paper also reports on a method of incorporating transition metal oxide(s) with the porous gold to form an active heterogeneous catalyst. Promoter elements can also be melted with AuAl2 to improve catalytic activity. Alloying has the advantage that the promoter element can be in contact on atomic level with the gold. In-situ xray photoelectron spectroscopy (XPS) studies have also been done on the porous gold catalysts to further clarify the CO oxidation mechanism on gold-based catalysts.

Oct 1, 2003

By L. J. Cabri

A gold sample assaying 11.4 g Ault was selected for this study. Approximately 99% of the gold in this sample occurs as discrete gold minerals; the balance occurring as invisible gold in pyrite (determined by SIMS analysis). The sample was coarsely ground and sieved, yielding -38, 17, 22 and 22 wt.% in the -400+160 um, -160+80 um, -80+40 µm and -40 µm size fractions. Assays of the size fractions gave a gold distribution of -32, 20, 21, and 27% respectively. Processing with the hydroseparator (model HS-02) gave two tailings products and one concentrate from each size fraction. Assays of the concentrate from each size fraction gave gold recoveries of -7, 7, 24, 19%, respectively. Polished sections were prepared from each hydroseparation product and studied by image analysis to automatically search for gold minerals. Calculations were done using the surface area of the grains of gold minerals found on the polished sections.

Jan 1, 2005