World demand and production of diamonds both for gem and industrial purposes has increased nearly five-fold during the past 25 years. Improved mining and recovery methods together with the discovery and development of new fields has enabled mining operations to fill the growing demands. Producing areas in South Africa, South West Africa, The Congo Republic, Angola, Ghana, Tanganyika and Sierra Leone account for over 95% of world production, estimated to be 26,000,000 metric carats, valued at $265,000,000 for the year 1959. Approximately 15 to 20% of the production is gem quality, representing about 70% of the total value.
Diamonds are recovered mainly from alluvial deposits which vary widely in character, often cemented; and usually contain large quantities of clay or a sticky slime fraction from near zero to about 50%. Substantial production also comes from Kimberlite pipes and dikes (Blue Ground), a basic igneous breccia, considered generally to be the originating source for nearly all diamonds. Diamonds have a specific gravity up to 3.52 and are associated with minerals such as magnetite, ilmenite, garnet, tourmaline, spinel, rutile, pyrite, quartz and other minerals which due to their specific gravity makes ….Read more
The production of gold bullion from gravity or flotation concentrates is often an important economic consideration for an isolated gold mining operation. It is assumed in this case that the coarse free gold has been recovered by the Mineral Jig in the grinding circuit and that the jig concentrate has been amalgamated. This treatment produces a portion of the gold (25 to 40 percent of the total) as amalgam, but the balance of the recoverable gold is present as non-amalgamable flotation concentrate together with the amalgamation residue. The problem is therefore, to develop a batch cyanidation procedure that will convert the gold contained in these products into bullion. A batch procedure is desired because of the small quantity of total concentrate (5 to 6 tons) produced daily and the greater flexibility and simplicity afforded by a batch type process.
Gravity and flotation concentrates that contain a portion of gold closely associated with sulphides may require fine grinding (—200 mesh) followed by pre-aeration and/or pre-agitation with lime prior to cyanidation in order to minimize the chemical consumption. Refractory gold concentrates may require roasting, but this ….Read more
The handling of large quantities of gold-bearing gravels is of utmost importance for most successful placer operations. In addition to providing efficient washing and recovery methods, the placer plant should be constructed as a compact unit that can be readily moved. This is an important consideration because the washing and recovery plant should be close to the mining area at all times to minimize the distance that the gravels must be transported. A second consideration is the necessity of providing a means for discarding the tailings.
The above flowsheet was developed to meet the foregoing requirements and has a capacity of approximately 50 cubic yards of bank-run gravel per hour.
FEEDING: The method of mining or excavating will depend on the local conditions such as thickness of gold-bearing gravels, amount of overburden, quantities of large boulders, water table, topography, etc. In this study, however, the deposit is mined using a dragline which dumps directly into the feed hopper. Large boulders are rejected by a heavy 8″ grizzly located on top of the feed hopper. The gravels are transported to the washing and concentrating plant by means of a belt conveyor. The ….Read more
The ore occurs as uraninite adhering to the outside of sand grains in the Wind River formation which rest unconformably upon Cretaceous shales. The ores are relatively low in clay content and generally regarded as exceptionally clean ores from the standpoint of objectionable impurities. The arkosic sands in which the ore occurs are very porous and permeable, having been laid down in scoured channels in the bentonitic clays.
Although extensive ore reserves in the area will require underground mining methods, significant ore reserves were also found near the surface which can be mined by open pit methods. All ore presently being mined by Petrotomics Company is by open pit under contract to Plateau Construction Company of Rawlins, Wyoming. Initial stripping of 2.3 million yards of overburden started in July, 1959 using Euclid TS24 scrapers and Euclid tractors for pushers. The ore zone is mined using a 2-yard Bucyrus-Erie shovel and a Koeh-ring shovel equipped with a backhoe front and also a crane front for drop ball use. Euclid trucks of 14.7 yard capacity with heated boxes are used for haulage to the mill which is one-half mile away. Ore control is stressed and accurately followed.
Future mining will utilize backfilling ….Read more
The treatment of copper ores, both oxides and sulfides by means of flotation, hydrometallurgy or other processes has been well established for many years. Flotation has been applied generally to the treatment of sulfide ores, both in small and large scale operations.
Hydrometallurgical methods alone or in combination with flotation have mainly been applied to large tonnage operations to recover copper from low grade native copper, oxidized, or mixed oxide and sulfide ores that are not readily concentrated by flotation alone or by other means, either due to treatment costs or low recovery. The treatment of smaller tonnages of such ores by hydrometallurgy has not been widely employed due to high capital plant costs.
Acid Leaching Process Flowsheet
The method of dissolution by sulfuric acid and ferric sulfate with chemical precipitation by means of scrap or sponge iron appears to offer the best potential for wide application and low costs. Its basic chemistry is not complex but its economic application is dependent on handling of materials and solutions by such procedures to insure low operating costs.
The flowsheet discussed in this study is for treatment of 100 tons per day oxide-sulfide copper ore by the leaching process using sulfuric acid-ferric sulfate solvent. This flowsheet ….Read more
In the metallurgical treatment of uranium ores large tonnages must be handled. Many ores are low grade so it becomes necessary to employ systems which can be operated on a continuous basis at low cost. A vast amount of research has gone into the development of suitable processes. One is solvent extraction, which has proven extremely efficient and simple in operation. Diligent work has gone into selection of the proper solvents. The solvent is a high flash point kerosene with 10% by volume of Di-2-ethyl hexyl phosphoric acid and 2.5% primary decyl alcohol or tributyl phosphate. It is lighter than and immiscible with water.
Uranium Processing Flowsheet
Uranium processing flowsheet
The flowsheet is generally applicable on sandstone and limestone ores containing uranium in the form of acid soluble carnotite and roscoelite. The values are dissolved with sulphuric acid and lime content is limited to about 6% to avoid excessive acid consumption. Dissolved uranium is extracted from the clarified and adjusted pregnant acid solution by the solvent extraction method, then the values are stripped out of the solvent and precipitated in the usual manner as yellow cake. Vanadium, if ….Read more
The plant was originally designed to treat uranium ores with low lime-high vanadium content from the Lukachukai Mountains. The process utilized is known as the “Acid Cure” and had been developed for the most part by the AEC to increase recovery of vanadium values. Briefly, it involved “pugging” the ore with 10% water and 400-500 lbs. of concentrated sulfuric acid. The product was allowed to cure for six or more hours to convert the uranium and vanadium values into water soluble salts. Acid consumption and labor resulted in high costs. With the increased mill capacity, the character of the ore feed from the new sources of supply changed to high lime-low vanadium content. The market for vanadium fell off and the AEC modified the milling contract to eliminate vanadium recovery. With the importance of vanadium recovery removed, and in order to reduce processing costs to a minimum, the method of processing was changed from “Acid Cure” to the “Raw Leach” method described in this article.
In addition to the change over to the “Raw Leach” method of processing, major changes have been made in the method of extracting uranium and vanadium values from the pregnant solutions. For the past 18 ….Read more
The Abbott mercury mine and mill are situated at an elevation of 2,000 feet in Lake County, California, approximately 24 miles west of Williams on State Highway 20 towards Clear Lake. Williams, which is served by the Southern Pacific railroad, is a local supply point as well as Colusa, located 10 miles east of Williams on State Highway 20.
The mine was discovered in 1862 and made its first recorded production in 1870. Operation of the mine has been interrupted by periods of low mercury markets and by an interval of litigation. The four main productive periods have been 1870-1879, 1889-1906, 1941-1946, and 1952 to the present. Total production is in excess of 50,000 flasks (76 pounds) which ranks it about tenth among California mercury mines in all-time production. The property was acquired by COG Minerals on August 7, 1958.
The Abbott ore bodies are contained in dikes and sills of serpentine breccia which make up a northwest trending complex some 2½ miles long and from 275 feet to 2,500 feet wide. This breccia was intruded cold into lower Cretaceous sediments on the southwest flank of the Wilbur Springs anticline. On the southwest or hanging wall side of the serpentine, and in ….Read more
Aerial view of the Opemiska Copper Mines (Quebec) Ltd., Mill Buildings and Shaft Area.
The Opemiska mine property is in Levy Township in Chibougamau area of Quebec and is comprised of 487 acres of patented claims contiguous with 2,215 acres held under development license. The townsite of Chapais which serves the mine community is complete with all the necessary services including housing, schools, churches, hospital, recreation center and stores. Direct railway service is provided by the Canadian National Railways to Western Quebec and the Lac St. Jean district. There is a highway connection via Chibougamau, a distance of 160 miles to St. Felicien near Lac St. Jean. Telephone, telegraph and scheduled air services are available.
The mine shafts, milling plants and other facilities on the property are strategically located on the northern slope of a large rock outcropping. Lying below and to the northwest is the tailings disposal area while on the opposite side of the outcropping, extending to the southeast, is the townsite of Chapais.
The original mill at Opemiska began production on December 8, 1953, at a rate of 400 tons per day. Operations were centered around the Springer No. 1 shaft. In ….Read more