Only where a group of mines operates in a single district are costs comparable and then only with reservations. In general, cost systems are fairly uniform, yet in studying costs of a number of plants it is noticeable that in some cases there is a tendency to omit certain operations which are proper charges against ore dressing and treatment. These should cover the first stage of coarse crushing, whether it be underground or on the surface, as well as the disposal of the residue, the recovery of bullion, and returns from products sold and must include the cost for labor, power, supplies, repairs, and compensation.
In 1936 when data were being compiled for Cyanidation and Concentration of Gold and Silver Ores, considerable published information was available on milling costs in various parts of the world. At the present time, however, it is extremely difficult to obtain reliable figures on the cost of ore treatment owing to the fact that during a period of rising prices and wages the mine managements do not consider current cost data typical of normal operation and are unwilling to release them for publication.
Another factor which applies particularly to the United States and Canada and which tends to make cost-per-ton figures unreliable is the disparity between the rated capacity of many of the mills and the actualtonnage being handled today. This is partly attributed to shortage ofunderground labor and partly to the fact that during the war period not only was maintenance heavier than normal but opportunities for improvements in technique were lacking.
Figure 97 shows the relationship between the tonnage capacity and total milling cost, per ton based on the 1939 figures for a number of typical Canadian plants. Saving in overhead and labor is the principal factor that enters into the decreasing cost per ton for the larger operations.
Considerable variation will be found in individual cases depending upon hardness of ore, fineness of grind, hours of treatment required, reagent consumption, and the situation of the property in its bearing on cost of supplies, etc.
The total cost of producing an ounce of gold in Canada increased from $22.35 in 1939 to $32.07 in 1945, according to the report of the director of the Ontario Mining Association for 1945. This represents a 43.5 per cent increase. From various other data which are available, however, it appears that milling and treatment costs (mining excluded) have probably not risen on the average over about 30 per cent. The broken line in Fig. 97 indicates estimated present (1948) average cost on the basis of this 30 per cent rise.
Kerr Addison, for instance, is milling 2800 tons per day for a total of 72 cents per ton. Hollinger in the 40 weeks ending Oct. 6, 1948, milled an average of 3627 tons per day at a total cost of 77.29 cents per ton, of which 37.90 cents was labor cost.
Where a combination of flotation and cyanidation is used, the combined cost approximates this same percentage. This includes such items as heating and lighting, sampling, assaying, experimental work, repairs, and various indirect costs, depending upon the system of cost distributions in use. It is partly because widely different methods of charging out such costs have been adopted that considerable divergence in overall cost distribution is to be found.
Consolidated Beattie gold mines is a good example of a large plant employing flotation, roasting, and the cyanidation of concentrates. Approximately 1300 tons per day of arsenical gold is treated for an overall cost of $1.05 per ton, distributed as shown in Table 98.
The roasting cost works out at approximately $1.22 per ton of concentrate, distributed as shown in Table 99. At MacLeod Cockshutt Gold Mines, Ltd., the cost of roasting in 1941- 1942 was 32 cents per ton milled or $1.25 per ton of ore roasted, while at Lake Shore mines for the same year the cost was about 80 cents per ton roasted.
The 700-ton mill operated by the Standard Cyanide Co. in Nevada between the years 1939 and 1942, when it was closed as a result of government order during the Second World War, succeeded in making a profit from ore carrying as little as 0.06 oz. gold per ton. Cheap, open-pit mining methods were used, and good extractions were obtained when grinding to only 3 mesh. These, among other factors, made for extremely low-cost operation. The 596,482 tons milled yielded $1.86 per ton at a total cost of $1.18 per ton of which $0.52 was milling cost.
The power required in cyanide plants varies with type of ore, fineness of grind, etc., but in general the range is 20 to 30 kw.-hr. per ton of daily capacity. The power distribution at Preston East Dome mines in Ontario, Canada, is shown in Table 102. The relative distribution of power between the crushing and grindingsections will vary according to the fineness of crushing and the type of plant, but on the average these departments will together consume 60 to 70 per cent of the total power.
Flotation. The power consumption for straight single-product flotation plants varies, according to A. M. Gaudin, from 12 to 20 kw.-hr. perton, depending on the fineness to which the ore is ground. The average percentage power costs for the various.departments of seven United States producers is given in Table 103.
The power consumption at Randfontein Estates, which is milling 13,000 tons per day by the older sand-slime process, is shown in Table 104. Distribution figures for the new 2100-ton-per-day Marievale plant are shown in Table 105.
A small gold mine flowsheet is shown below together with cost data which clearly shows the results that can be obtained when handling a low grade ore by a simple process. There are many commendable features in such a set up and no complicated machines or practices are embodied in this plan. In fact, its simplicity is appealing and the results obtained prove the practicability of this flowsheet.
The rod mill product passes over a roughing table where a high grade gold concentrate containing most of the free mineral is sent directly to a Clean-Up Pan. The middlings from the table are sent directly to an 8-cell Sub-A Flotation Machine from which a high grade concentrate is obtained. The tailings from the flotation machine are sent over a pilot concentrating table for visual examination. A middling pump and a dewaterer can be installed to take care of the middlings for regrinding, should enough value be found in them to warrant such a treatment. In this concentrating mill, however, it has been found that the middling product is of so little value that it would not be economically profitable to regrind and retreat this product. The cost data above referred to has been compiled from actual operating results and shows the cost of milling both for the old 50-ton plant and the new 100 ton concentrator, as is now in use. Note the reduction in milling costs through the use of the new flowsheet which includes an 8-cell Sub-A Flotation Machine. The savings made in lower operation costs and lower maintenance costs are noticeable and this saving was also made in the face of a 12.5% increase in wages made when the new plant was started.
Many of our so-called small gold mines or low grade deposits could well take this simple and inexpensive flowsheet for an example and be rewarded by a good profit per ton of ore treated, if the owners or operators would adhere to these principles. These are namely a simple crushing, grinding, concentrating, and flotation circuit without frill or fancy theories, but with a constant supply of ore through the mill at a nominal profit per ton, operating continually 24 hours per day. In other words, it may pay to have a lower recovery with a higher net profit than a higher recovery with an actual loss.
You will note from the above chart, the fairly high cost of marketing concentrates, but with the addition of the Clean-Up Pan a large portion of the free gold can be recovered in the form of amalgani and then reduced to bullion for shipment direct to the mint. The treatment of concentrates even of a complex nature is now standardized and should result in additional profits.
To aid in arriving at approximate operating costs, we are giving four charts with curves showing operating costs for the different standard methods oftreating ores. These charts show the costs compiled from actual operating figures secured from a number of mills operating under varying conditions. These figures show that operating costs do not increase greatly as one would naturally suppose when smaller tonnages are handled.
In studying the various factors affecting milling costs, the one point that is most noticeable is the effect of operating time on these costs. Plants thathave mechanical difficulties show costs greatly in excess of those with full operating time working under comparable conditions, and this demonstrates clearly the importance of having fool proof and ruggedly designed machinery that will run 24 hours per day. Modern milling equipment must be able to take care of overloads and handle oversize material without choke-ups and the resulting shut-downs. One must always keep in mind that after all a machine, a mill, or a process is only as strong as the weakest link.
The EXAMPLE Gold Mine Operating Manual has been prepared to provide a practical reference for operators in the EXAMPLE Gold Mines Processing Plant. This manual contains basic information about the process and equipment used in the process. Each unit is identified by name and equipment number. The function of each unit, a process and control description, and operating information is discussed. The last two sections deal with general plant safety and the definitions of terms used in the context of the processing plant.
This manual is intended as a general guide to plant operations. It is NOT intended to supercede, contradict or in any way negate manufacturers instruction manuals, which contain detailed information about each piece of equipment. In the case of uncertainty or requirement for clarification and/or further details, readers are to refer to the manufacturers manuals.
The EXAMPLE Gold Mill is designed to process 500 tonnes per day of ore. The flowsheets are conventional and consist of two stages of crushing, single stage ball mill grinding, cyanidation and a Merrill-Crowe precipitation circuit for gold and silver recovery. In addition to the cyanide circuit, gold leach residue is treated in a flotation stage to recover un-leached silver (Argentite) minerals. This circuit is followed by a small cyanidation circuit for recovery of silver (and remaining gold) from the flotation concentrate. Precipitated gold and silver are refined in an induction furnace to produce dore bullion.
The crushing plant will operate independently of the mill. In addition, whereas the mill will be primarily run from local start/stop stations, the crusher is designed to be run from its control panel. The dividing point between the two plants lies at the fine ore bin; all equipment prior to this bin is considered in the Crushing Plant and all equipment subsequent to it in the mill.
Sand, because of its many uses, has become a very important commodity in the world. It can be used for a wide variety of purpose ranging from as simple as filler on your flower vase, layers on your gardens, a material for art crafts and projects, to the some of the most complicated use like manufacturing of glass and sandblasting.
But the major industry that uses different types of sands is the construction. Sands are used in constructing residential houses, buildings, bridges, dams, and just about anything that involves concrete structure.
It is said that cost of sand in itself is very cheap, what makes it worth the price tag it has now are the process it has to go through to get to its intended destination, most likely a construction site. As sands mostly come from quarry sites, all the process involved for it to be available for commercial use hugely affect their price. The extraction from the site, the sifting, the washing, the hauling, the loading, the transporting, the quarry and selling permits, the taxes, among all other cost considerations take part in the costing of sands.
For medium to large projects, sand purchases are typically per ton. To give you an idea, one ton of sand typically covers 35 square feet, one inch thick if you are using either the masonry sand or the river sand. A ton of granite sand typically covers around 75 square feet, two inches thick.
Thecost of sand per tondepends on the kind of sand as there are several types used in many different projects. But the most common type of sands like the ones mentioned above cost around $25 to $40 per ton.
Some construction materials vendors also sell sands per cubic yard, or specifically, per half cubic yard.A cubic yard of sand weighs around 2,500 lbs. while a ton is equivalent to 2,000 lbs. Therefore, a cubic yard is equivalent to 1.25 tons or a ton of sand is equivalent to 0.8 cubic yard.
What is included in thesand pricesdepends on the quantity you intend to purchase. In large quantities, they typically include the cost of the sand material as well as the loading of it into your truck. This is if you think it is cheaper to pick up the sand rather than have it delivered to your project site.
Thesand pricesindicated in different sellers price list are exclusive of delivery fees unless otherwise specified. So, to give you an idea, the delivery charge ranges anywhere between $50 and $100, depending on how far the delivery site is from their storage or quarry site.
The properties of fine sand can be associated with river sand, which, as the name suggests, are obtained from river banks. It is usually whitish-gray in color and is mostly used in plastering. The artificial sand or M sand can also be an alternative to river sand.
This is also known as pit sand which is also popularly known as Badarpur. The sources of this type of sand are deep pits and the coarse sand typically has a red-orange color. Its grains are sharp and angular. They are mostly used in concrete.
Prominer maintains a team of senior gold processing engineers with expertise and global experience. These gold professionals are specifically in gold processing through various beneficiation technologies, for gold ore of different characteristics, such as flotation, cyanide leaching, gravity separation, etc., to achieve the processing plant of optimal and cost-efficient process designs.
Based on abundant experiences on gold mining project, Prominer helps clients to get higher yield & recovery rate with lower running cost and pays more attention on environmental protection. Prominer supplies customized solution for different types of gold ore. General processing technologies for gold ore are summarized as below:
For alluvial gold, also called sand gold, gravel gold, placer gold or river gold, gravity separation is suitable. This type of gold contains mainly free gold blended with the sand. Under this circumstance, the technology is to wash away the mud and sieve out the big size stone first with the trommel screen, and then using centrifugal concentrator, shaking table as well as gold carpet to separate the free gold from the stone sands.
CIL is mainly for processing the oxide type gold ore if the recovery rate is not high or much gold is still left by using otation and/ or gravity circuits. Slurry, containing uncovered gold from primary circuits, is pumped directly to the thickener to adjust the slurry density. Then it is pumped to leaching plant and dissolved in aerated sodium cyanide solution. The solubilized gold is simultaneously adsorbed directly into coarse granules of activated carbon, and it is called Carbon-In-Leaching process (CIL).
Heap leaching is always the first choice to process low grade ore easy to leaching. Based on the leaching test, the gold ore will be crushed to the determined particle size and then sent to the dump area. If the content of clay and solid is high, to improve the leaching efficiency, the agglomeration shall be considered. By using the cement, lime and cyanide solution, the small particles would be stuck to big lumps. It makes the cyanide solution much easier penetrating and heap more stable. After sufficient leaching, the pregnant solution will be pumped to the carbon adsorption column for catching the free gold. The barren liquid will be pumped to the cyanide solution pond for recycle usage.
The loaded carbon is treated at high temperature to elute the adsorbed gold into the solution once again. The gold-rich eluate is fed into an electrowinning circuit where gold and other metals are plated onto cathodes of steel wool. The loaded steel wool is pretreated by calcination before mixing with uxes and melting. Finally, the melt is poured into a cascade of molds where gold is separated from the slag to gold bullion.
Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.
Our concentrates come from the amount of dirt we take from our gold mine and run through the trommel. All the lighter sand is washed out while all the gold and the heavy sand stays in the sluice. This is a natural process no gold is taken out or added!