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By William Gleason

"There are signs that the commodity downturn that has battered the mining industry for the past five years is beginning to ease up. As the dust begins to settle and mining companies begin to take stock of the battle, Newmont Mining Corp. will be one that is standing strong with just a few scrapes and bruises thanks in large part to the leadership of president and chief executive officer Gary Goldberg and his right hand man and chief operating officer, Chris Robison.As he closes in on retirement (for a second time) Robison, a third-generation miner from Nevada, took time to speak with Mining Engineering about a 33-year career in which, among other things, he is credited with not just helping Newmont survive the turbulent times but with steering the company to a safer, more productive and more profitable heading.“I think we did it better than anyone else,” Robison said when asked how the company fared during the past five years. “We didn’t talk about it a lot, we just put together a strategy and we delivered.”What Newmont, the world’s second-largest gold mining company by production, delivered since Robison took the position of chief operating officer in 2013 are improvements in costs, porduction, projects and safety.Operating under the mantra of “live within your means,” Robison was pulled out of retirement from Rio Tinto and into a challenging situation at Newmont. The price of gold was in a nose dive from a high of nearly $58/g ($1,800/oz) and heading to levels closer to $38.60/g ($1,200 oz).“Newmont is a big ship that can’t be turned, but has to be steered,” said Robison. “We recognized that we had to set a new course. The direction the ship was going was great for $1,600 to $1,800/oz gold but we were chasing ounces.”Like the rest of the gold mining sector before the falling gold prices, Newmont was focused on volume and was looking for gold wherever it could be found. The slogan at Newmont in 2011 was “7 million ounces a year by 2017.”When Robison came on board it was a different reality.“We had to begin focusing on value over volume as the cornerstone of Newmont going forward,” he said."

Aug 1, 2016

By Zemin Ma

A novel chromate [Cr(VI)] reducing bacterium was isolated from chromite ore processing residue disposal site of China and identified as a Leucobacter sp. by 16S rRNA gene sequence homology. The minimum inhibitory concentration of strain CRB1 was 820 mg l-1 of Cr(VI). The reduction of Cr(VI) occurred only under aerobic conditions. With an initial concentration of 2.5×108 cells ml-1, 1800 mg l-1 of Cr(VI) was reduced entirely within 38 h under the optimum conditions, at 30 °C and pH 9.0. Increasing Cr(VI) concentrations prolonged reduction process and higher cell densities meant quicker reduction. A blue precipitate was produced during chromate reduction of strain CRB1, which was binding to the surface of bacterial cells and determined as trivalent chromium with electron paramagnetic resonance (EPR) spectrometry. The conspicuous chromate reduction ability of Leucobacter sp. CRB1 suggested a potential for bioremediation of Cr(VI) containing wastes.

Jan 1, 2008

By J. W. Craig

CHROME ore, which is used in Canada in the production of ferro-alloys, in a variety of refractories, and indirectly in many chemical industries, is both commercially important and scientifically interesting. The sight of chromium metal is familiar to all of us in the home, the office, the automobile. Chromium is synonymous with armaments: it is understood to be one of several essential metals in tanks, which played an important role in the defeat of France in the spring of 1940. Chromium, in other forms, comes into our daily lives by way of paint and leather, of the familiar green ginger-ale and beer bottles, and more indirectly in every pound of steel produced in the .Dominion. Necessary to our civilization in peace and war, the ores of chromium occur in many corners of the earth. This paper attempts to describe the chemical constitution of chrome ores, their world distribution, and the various chrome products and their industrial applications in Canada.

Jan 1, 1940

By Bill Shand

"Placer Dome - Campbell Mine is a gold mine located at Balmertown in the Red Lake District of North Western Ontario. During the last 50 years, the mine has produced over ten million ounces of gold.A change in ball mill grinding media was made in August 1998 from 1.5” diameter forged balls to 1.5” diameter, 18% chrome balls. This was done to reduce grinding media consumption and to potentially help flotation performance.A marked ball test done in September-October 1999 showed that, of the alloys tested, 18% chrome was the optimum for the ore at Campbell Mine. The test showed that consumption of chrome balls should be 3 times less than forged balls.In December 1999, the ball size was increased from 1.5” to 2” in an effort to reduce the amount of oversize rock discharging from the ball mill. This change in size was successful.Grinding media consumption for the ball mill decreased 73% from 1.20 kg/tonne before the use of chrome balls to 0.327 kg/tonne after the use of chrome balls. This clearly indicates that, for the ore at Campbell Mine, there is significant savings in grinding media by using chrome.Grinding ball costs were reduced by 59% from $O.88/tonne of ore milled to $0.36/tonne of ore milled representing a saving of $298,000 per year. This also clearly indicates that using chrome balls is a benefit at Campbell Mine.Test work to show that chrome grinding media is beneficial to flotation has been inconclusive so far but is still ongoing.No tests have been done to see if there would be a benefit with an even higher chrome percentage in the grinding media. Test work in this area is also planned for the future"

Jan 1, 2001

By Patricio Ruz, Gabriel Riveros, Carolina Ramirez, Andrzej Warczok, Rober Treimer

"Continuous converting of copper matte produces slag with high cuprous oxide content. The corrosion of chrome-magnesite refractories with slag of high cuprous oxide content is a major problem. Properties of olivine type of slag make the slag very attractive for matte smelting and converting.Analysis of phenomena determining the slag infiltration into the porosity of a refractory and dissolution of refractory components in the slag allowed for better understanding of the mechanisms of refractory destruction.The results of laboratory scale tests of the olivine slag infiltration into open porosity and corrosion showed dominating effects of slag temperature and cuprous oxide content. The optical and X-ray examination of slag samples permitted the definition of the mechanism of formation of new phases and refractory deterioration. 71"

Jan 1, 2009

By Ernest Burchard

A RECONAISSANCE of the chrome and manganese'1ore deposits of Culm was made in the spring of 191s by Albert Burch representative of the U. S. Bureau of Mines and the writer representing the U. S. Geological Survey. The object of the study was to obtain authentic information for use of the: United States Government as to the location, character, size, and availability of the Cuban deposits of the ores of these important steel-alloy metals. The Cuban Government courteously detailed Sr. E. I. Montoulieu, a mining engineer connected with the Treasury Department, to act as escort and associate throughout the work on the Island. Mr. George A. Wright, of Baracoa, Cuba, a mining engineer especially familiar with the chromite deposits of Oriente Province, was a member of the party from Feb. 25 to Mar. 20. It was possible to visit most of, the chrome-ore deposits that seemed to be of promise, but there was not sufficient time to visit all that were brought to our attention, some of which may have merit. Furthermore, no attempt was made to examine the extensive chromiferous iron-ore deposits of the Mayari, Moa, and Cubitas districts, as these deposits cannot be regarded as sources of chromium except indirectly. At the close of the field work the essential data concerning the quantity and quality of ore probably available for shipment during 1918 and 1919, in the event of the continuation of the European war, and of the tonnage of ore in reserve, were furnished to such Government bureaus as were interested, including the Shipping Board and the War Industries Board, and as soon as chemical analyses of the chrome ores could .be obtained, a press bulletin on the subject was published by the Geological Survey. In the present paper the engineering data, and tonnage estimates contained in the unpublished notes of Mr. Burch have been freely used, and their helpfulness is hereby gratefully acknowledged. Many thanks are due Senor Montoulieu and Mr. Wright for their valuable work in the field; to the officials of the Spanish American Iron Co. and of the various other companies; and to individuals holding chromite claims, for courteously facilitating the work of the party. In the study of material for the present paper, chemical analyses have been made by R. C. Wells and petrographic determinations and descriptions were furnished by Miss E. F. Bliss, both of the U. S. Geological Survey.

Jan 9, 1919

By Harry M. Mikami

Chromite is the only ore mineral of metallic chromium and chromium compounds and chemicals. Because of this fact, chromite and chrome ore are used synonymously in trade literature. In commercial market quotations, chrome ore is the term commonly used. Chromite per se, because of properties imparted by its chromium content, is used in refractories and in special purpose moulding sands for metal casting. There are many other minerals containing some, generally minor, amounts of chromium, but none are commercial sources of the element (Thayer, 1956, p. 15). Chromium and chromite have many diverse uses that, directly and indirectly, critically affect vast segments of our modern industrial system. Most important are probably the metallurgical applications wherein chromium is a component of heat, abrasion, corrosion, and oxidation-resistant, and high strength alloys of many types. Stainless steels are the largest volume category of chrome-bearing alloys. Chromium chemicals are used in leather tanning, in pigments, dyes and mordants, printing, :hemica1 process industries, photography, pharmaceuticals, metal plating, pure chromium metal production, and for many other purposes. Chromite is a necessary constituent in basic refractories indispensable for the production of steel, copper, cement, and glass. Under present economic-political conditions, he U.S. and for that matter, North America, has virtually insignificant ore reserves of chromite. There are chromite deposits, as will be described, but they would only be used under highly abnormal conditions if all outside sources were cut off. All chromite used in the U.S. is imported from the eastern hemisphere in which are contained the principal world reserves. As the main suppliers in 1971-72 were the USSR, Turkey, Republic of South Africa, Philippines, and Rhodesia, the strategic nature of chromite is obvious.

Jan 1, 1975

By W. D. Johnston, T. P. Thayer

THE minerals that collectively are known as chromite form an isomorphous series of the general formula (Mg,Fe) 0. (Cr,Al,Fe) 203. So wide is the range in chemical composition in this group that chrome ore consisting entirely of the mineral chromite may range from less than 30 pct to more than 60 pct Cr203. The most comprehensive published data on the chemical com- position of chromite are by Stevens,62 who made complete analyses of 52 samples of chromite concentrate from many localities in North, Cen- [ ] tral, and South America. These samples were mechanically purified to remove associated silicates and might be regarded as the cleanest chromite that could be obtained by any mechanical milling process. Fig 1 shows the predominant zone of isomorphism, within the triangular prism of composition defined by the mineralogical end members of the series, wherein his analyzed samples fell.

Jan 1, 1949

Beach sands on the Morobe coast of New Guinea contain significant amounts of chromite. This chromite, together with the more abundant associated minerals such as olivine, enstatite, tremolite, antigorite and feldspar has been de- rived from rocks of the Papuan Ultramafic Belt and transported to the beaches by three rivers, the Paiawa, the Saia and the Sesimbai. Of the hundreds of samples taken, 26 have been analysed mineralogically and chemically in some detail. On this basis, five groups of samples, four on- shore and one offshore, representing character- istic mineral assemblages, have been recognized. The chromite grains themselves have been exam- ined to determine variations in amount and in the Cr/Fe ratio, since this is of economic importance. Much of the chromite fails to reach a high Cr/Fe ratio as a result of magnetite rims around chromite grains. The precious metal content of the sands is negligible.

Jan 1, 1973

By C. H. Stockwell

THE Eastern Townships of Quebec have been the chief Canadian source of chromite. Production, however, has never been large and, except for a period of steady but small output between 1894 and 1909, mining has been active only in war time. The known deposits are too small or too low grade to compete with overseas sources in normal times. During the last war, shipping difficulties and a greatly increased demand in the United States resulted in high prices and a ready market for low-.grade material. The Quebec chromite industry flourished and played an important part in relieving the wartime shortage. Shipments in 1918 .amounted to 15,600 tons of crude ore and 6,400 tons of concentrates. At the outbreak of the present war it was natural to turn again to the Quebec field as a possible source of this strategic mineral. Some of the old properties have since been opened by private and government money and some new deposits have been found. Total mill capacity is 750 tons per day, as compared with 200 to 300 tons in 1918. During 1940, 1941, and 1942, about 85 chromite deposits were examined by the Geological Survey in a belt 100 miles long and up to 7 miles wide. A part of this belt, about 35 miles long, in which the geological features ?were not well known, was mapped on a scale of 1/2; mile to an inch.? Small ..areas around some of the deposits were mapped in detail, on scales of 20 to 200 feet to an inch. Some geophysical work was done but did not result in the discovery of ore. Prospecting by stripping and trenching was then undertaken and chromite ore was uncovered at several localities. The above work was done by the writer and by J. W. Ambrose, who has kindly contributed his results for incorporation in this paper. Y. O. Fortier actd as assistant in the geological work and, in 1942, was in charge of a sub-party engaged in geological mapping. The author is indebted to H. C. Cooke and J. W. Ambrose for reading the original manuscript and for offering many helpful suggestions for its improvement.

Jan 1, 1944

By A. Acar, E. T. Tuzcu, Y. O. Vural

"In order to sustain the operations in chromite processing plants, due to concentrate selling cost, plants are in need of optimization in terms of capacity and recovery increase. In this study, DAMA Engineering carried out a methodological study for the purpose after a detailed sampling campaign in a plant which is situated in one the main chromite zones in Turkey; 1 The current status of the plant was investigated quantitatively with the bottlenecks, Plant overall efficiency in terms of recovery, Efficiencies of the particular equipment (mill, screen, gravity circuit), 2 A new circuit was proposed with the available equipment, 3 The new circuit that is product of modeling and experimental effort, was evaluated quantitatively as if it is a running plant, After 4-5 months continuous effort, the capacity of the plant was almost doubled (37 tph to 70 tph) and the plant overall recovery was increased from 48% to 63% by grinding adjustments and additional shaking tables theoretically. It was shown that the plant may move into profit with the minimum amount investment using readily available system. INTRODUCTION TO THE CURRENT PLANT The objective of the study is to increase the capacity and recovery of the chromite plant owned by Kurmel Group, Akmetal Inc. The complete study is given elsewhere (DAMA, 2016). The plant is situated in one of the main chromite zones in Turkey; Aladag. The current capacity of the plant is around 35 tph and the overall recovery declared by plant engineer is around 47 %. The chromite plant mainly has 3 units; crushing, grinding and gravitational circuits. The crushing circuit has 3 stages; a jaw crusher, a secondary cone crusher and a tertiary cone crusher operating in closed circuit with a vibrating screen with the aperture size of 15mm. In grinding circuit, a rod mill (2.44 6m x 3.6) and a ball mill (2.13 x 2.3m) are used for primary and secondary grinding, respectively. Derrick screens are used for the size separation. Additionally, for the size classification of the system, hydrosizers are used and each size fraction is sent to the shaking table sets. The middling product of the tables is subjected to re-grinding with a ball mill with the dimensions of 2.1 x 2.9 m. The capacity and the recovery are affected by several bottle necks; hydrosizers’ pure classification, primary/secondary mill power vs capacity problems, re-grinding product’s high slime content and so on. These combined factors made the plant to run in low recovery and capacity. Hence, DAMA was asked to make a study to investigate current status of the plant and propose a new solution to increase capacity and recovery of the plant. The conceptual flowsheet of the circuit is given in Figure 1 below."

Jan 1, 2017

By Charles J. Johnson

The United States is totally dependent on imports for all primary chromite and most ferrochrome supplies. Although the United States imports chromite and ferrochrome from a number of countries, the long-term future of chromite supplies appears to lie in southern Africa (Republic of South Africa and Zimbabwe) where 88 percent of known world reserves exist. Floreover, low mining costs and the availability of low-cost electricity for ferrochrome production gives South Africa a comparative advantage over most other chromite and ferrochrome-producing nations. A well-known problem faced by the United States is that when viewed from a longer-term perspective, the major sources of supply of metallurgical grade chromite and ferrochrome may be subject to disruption. The three countries that have caused the greatest concern have been the Republic of South Africa, the Soviet Union, and Zimbabwe. South Africa presents a particularly difficult problem because it may be subject to internal political unrest and/or U. N, economic sanctions. South Africa has increased its share of world chromium production from about 30 percent in 1968 to 62 percent in 1978.1

Jan 1, 1982

By N. McEwan

Keywords: refractories, chromite, Marico This paper examines the role of refractory-grade chromite in refractories. The chromite deposit at Verref?s Marico Chrome mine is described. The refractory properties of chromite and their role in basic refractories are described. The properties and metallurgical applications of chrome-containing refractories are described and finally environmental issues associated with chrome-containing refractories are discussed.

Jan 1, 2011

By N. S. Dalal, X. Shi

"Electron spin resonance measurements provide evidence for the formation of long-lived Cr(V) intermediates in the reduction of Cr(Vl) by glutathione redtuctase in the presence of NADPH and for the hydroxyl radical formation during the glutathione reductase catalyzed reduction of Cr(Vl). Hydrogen peroxide suppresses Cr(V) and enhances the formation of hydroxyl radicals. Thus Cr(V) intermediates catalyze generation of hydroxyl radicals from hydrogen peroxide through a Fenton-like reaction. Thus the mechanism of Cr(VI) toxicity might involve the interaction between macromolecules and the hydroxyl radicals.C(Vl) compounds have been found to exert serious toxic and carcinogenic effects on humans and animals (1-3). In contrast, most Cr(III) compounds are relatively nontoxic, noncarcinogenic, and nonmutagenic (1,4). Cr(VI) and Cr(III) oxidation states are different in their metabolic pathways: Cr(VI) , ions are rapidly transported across cellular membrane (1,4,5), while Cr[III) moieties do not easily penetrate cells and are not oxidized by cellular constituents (!). Since it is known that the reduction of Cr(VI) ion is required for its reaction with DNA (1), the molecular mechanisms for the intracellular Cr(Vl) reduction has been the focus of current studies but the details are still not understood.Earlier studies on the mechanism of Cr(Vl) reduction include those on the reduction of Cr(VIJ by glutathione (GSH) .0,6-8), ascorbic acid (9), glucose (10), lactose (IO), galacturonic acid (11), microsome (12), and mitochondrial electron transport chain complexes (13). These studies have shown that the Cr(VI) reduction involves the formation of Cr(V)-containing species which are often considered to be the toxic form of chromium. Thus far, however, no information is· available on the subsequent fate of those biologically formed Cr(V) species, in particular employing well defined biochemical systems. In this context, we report here our investigations of the reduction of Cr(VI) by glutathione reductase (GSSG-R). This enzyme was selected because it is ubiquitously present in cellular systems and it has been postulated to be involved in the Cr(VI) reduction (14-17) but the underlying mechanism has not been clarified. We find that the reduction proces·s involves not only Cr(V) but also ·OH radicals. We further investigate the reactivity of Cr(V) and find that it catalyzes generation of OH radical from H2O 2 through a Fenton-like reaction. The role of ·OH in Cr(VI) carcinogenicity is suggested from this study."

Jan 1, 1989

By Frederick M. Becket

AFTER all the chronology that has been given, what is the present status of chromium steels? For the purpose of this discussion the different types of chromium steels can be divided into three classifications-those containing relatively low , percentages of chromium, say 5 per cent or less; the medium-chromium steels containing up to about 18 or 19 per cent chromium; and the steels containing still higher percentages of chromium, and some of the special alloys. Chromium has some unique effects in steel, so it is well to make a few generalizations. The affinity of chromium for carbon is great and the metal is unique in the manger in which it supplements and enhances the effects of carbon. Chromium retards -considerably the thermal transformations on cooling and exerts an opposing influence both on the absorption and precipitation of the carbides in steel. These statements make it easy to understand the fact that chromium .steels are capable of producing a hardened product at a much slower rate of cooling than is, true of plain carbon steel, and that chromium carbide or -the mixed carbides of iron and chromium do not contribute to brittleness to as great a degree as does iron carbide.

Jan 1, 1929

By X. Pan

Slag-metal equilibrium experiments were conducted at 1500ºC and 1580ºC under 0.03 atm, 0.05atm and 0.83 atm CO partial pressures using silica and Cr-oxide crucibles. The complex slags belonged to SiO2-CaO-Al2O3-MgO-FeOx-CrOxand the metal phase to the Cr-Fe-C-Si-(S)systems. The carbon saturation of the metal phase was avoided using oxide crucibles and thus the results are pertinent to ferrochromium refining slags and processes. From equilibrium data and thermodynamic calculations the CrO /(CrO+Cr2O3) ratio in the slag was determined as 0.75, 0.80and 0.86 under 0.83 atm and 0.05 atm of CO pressure at 1500ºC and 0.03 atm and CO pressure at1580ºC respectively. The results clearly demonstrated that a higher chromium content of the metal results in higher Cr in the slag, and chromium in slag decreases with increasing SiO2. The results were also sensitive to the crucibles used as these oxide crucibles saturated the slag either with respect to SiO2or Cr-oxides. It was also demonstrated that the relative amount of CrO in the slag was higher when SiO2crucibles were used in accord with thermodynamic calculations. Iso-concentration curves for carbon and chromium of the metal phase in equilibrium with the slag were drawn on pseudo ternary SiO2–(AI2O3+CaO+MgO)–(Cr2O3+Fe2O3) diagram. The activity coefficients and activities of carbon and chromium of the metal phase were also calculated from the experimental data and available thermodynamics information and were plotted as iso-activity curves in the same pseudo ternary diagram. Keywords: Chromium, slag, equilibrium

Jan 1, 2004

By X. Pan

Slag-metal equilibrium experiments were conducted at 1500ºC and1580ºC under 0.03 atm, 0.05 atm and 0.83 atm CO partial pressures using silica and Cr-oxide crucibles. The complex slags belonged toSiO2-CaO-Al2O3-MgO-FeOx-CrOxand the metal phase to the Cr-Fe-C-Si-(S) systems. The carbon saturation of the metal phase was avoided using oxide crucibles and thus the results are pertinent to ferrochromium refining slags and processes. From equilibrium data and thermodynamic calculations, the CrO /(CrO+Cr2O3) ratio in the slag was determined as 0.75, 0.80 and 0.86 under 0.83 atm and 0.05 atm of CO pressure at 1500ºC and 0.03 atm and CO pressure at1580ºC, respectively. The results clearly demonstrated that a higher chromium content of the metal results in higher Cr in the slag, and chromium in slag decreases with increasing SiO2. The results were also sensitive to the crucibles used as these oxide crucibles saturated the slag either with respect to SiO2or Cr-oxides. It was also demonstrated that the relative amount of CrO in the slag was higher when SiO2crucibles were used in accord with thermo-dynamic calculations. Iso-concentration curves for carbon and chromium of the metal phase in equilibrium with the slag were drawn on a pseudo ternary SiO2? (AI2O3+CaO+MgO) ?(Cr2O3+Fe2O3) diagram. The activity coefficients and activities of carbon and chromium of the metal phase were also calculated from the experimental data and available thermodynamics information and were plotted as iso-activity curves in the same pseudo ternary diagram. Keywords: chromium, slag, equilibrium

Jan 1, 2004

The residues produced during the incineration of leather scraps contain significant amount of chromium which can be recovered and reused in the tanning industry. The objective of this study is to develop a cost effective method for chromium recovery from leather ashes produced during the incineration of leather scraps using a fluidized bed incinerator. The entire process investigated involves fusion of leather ash with sodium carbonate in air to oxidise chromium to sodium chromate, leaching with distilled water to dissolve chromates, and chromium reduction from the hexavalent to trivalent state by sodium thiosulphate solution. The main factors affecting chromium extraction, such as temperature, reaction time, and sodium carbonate to leather ash ratio, were investigated. Based on the results obtained, almost 100% Cr extraction can be obtained at 700°C fusion temperature, sodium carbonate to ash weight ratio equal to 3 and retention time longer than 50 min.

Jan 1, 2006

By Petr Dvorak, Jana Selucka, Hong Vu, Petra Starkova, Tomas Frydl

Waste, generated during high pressure leaching of lateritic nickel ores, contains about 50% of iron in form of magnetite but high chromium content ( *3%) does not allow its extensive utilization as the raw material for pig iron production in blast furnace. The chromium removal from the waste was carried out by two methods: (1) oxidative alkali roasting with NaOH and/or Na2CO3, followed by water leaching and (2) oxidative leaching in KOH sub-molten salts solutions. The results show that about 90.1% of Cr was removed when the waste was roasted at 900 °C for 3 h with 33.1 wt% of NaOH. The removal of 88.2% of Cr was achieved if the waste was roasted at 900 °C for 3 h with 40 wt% of Na2CO3. The sodium content in the water-leached residues was reduced from 5% to about 0.5% by reaction with CaO in aqueous solutions at 80 °C for 2 h. About 70% of Cr was removed if the waste was leached at 190 °C in 73 wt% KOH for 8 h.

Mar 1, 2017

Chromium, a critical mineral for which the United States is largely dependent on foreign sources, is the subject of a new report just issued by the Interior Department's Bureau of Mines. The report is the first in a new series called "Mineral Commodity Profiles" (MCP's). Designed to give an updated review of important events affecting critical minerals, it also presents a comprehensive description of industry structure, supply-demand relationships, technology, and outlook for the future.

Jan 1, 1977