How can i get heap of gold dust

For example, at the Beal Mountain Mine in Montana which closed in , cyanide seeped into groundwater that feeds neighboring trout streams, resulting in cyanide violations in those streams long-after the mine closed. Today's hardrock mining industry too often spills cyanide, billions of gallons of contamination released into the environment since the s.

Spills and leaks — which continue to this day — endanger the environment, wildlife and humans. Cyanide Use in Gold Mining. What is cyanide? Cyanide is a rapidly acting, potentially deadly chemical. How is cyanide used in mining? There are two types of leaching: Heap leaching : In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant collection pads. Vat or tank leaching : The ore is mixed with cyanide solution in large tanks.

Check—not on the board, but on the show, and my family and friends. Was I creative every day? Was I taking care of my spiritually? All this means is: I was alive. Might as well enjoy it. Might as well love it. Might as well immerse myself in it.

But what a story! You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Skip to content. Here are a few of the most common reasons I see that startups fail: Reason 1: Market Problems A major reason why companies fail, is that they run into the problem of there being little or no market for the product that they have built.

Reason 2: Business Model Failure Entrepreneurs are too optimistic about how easy it will be to acquire customers. Reason 3: Poor Management Team An incredibly common problem that causes startups to fail is a weak management team.

Weak management teams make mistakes in multiple areas: They are often weak on strategy, building a product that no-one wants to buy as they failed to do enough work to validate the ideas before and during development. The ore is then excavated by front-end loader and hauled by truck to the adjacent spoil-disposal area. One side of the slot is being excavated and removed while new ore is being added on the other.

It takes 60 days for this moving slot to traverse the entire pad length. The production schedule does not allow variation in the leaching cycle. As many as 60 individual pads were originally planned at this operation. At a heap height of 20 ft, each ft by ft pad is capable of holding 90, tons of ore. The chemistry of the pregnant solution from each pad is monitored individually.

This allows the leach cycle on individual pads to continue for as long as it is profitable. A total of two or three leach cycles is applied to each heap over a period of 9 months to a year.

Ini- tially, a to day leach recovers 55 to 60 percent of the gold values. A second leach is usually conducted after the heap has gone through a winter. An additional 2 to 5 percent of the total gold is recovered in the second leach.

Depending on production schedules, a third leach cycle may be used. Although reusable asphalt pads were considered, they were not used because being able to releach the ore over extended times was desirable and because they wanted to avoid the cost of moving the ore twice. After a heap has been leached, a second lift of ore is placed on it and the cycle repeated.

Comprehensive state-of-the-art construction and quality control tech- niques have been developed and are being used during pad construction at the larger operations and at small operations of established companies.

Com- petent and qualified managers and engineers direct the design and installa- tion of these expensive systems. For example, quality control checks include frequent destruction testing of seams and materials during the installation of synthetic liners.

Some small, undercapitalized operations, however, may not have adequate ability to construct pads and liners, and the integrity of these installations may be questionable. Internal berms are sometimes constructed in leach pads. These berms, which run from side to side in the direction of the slope of the pad, internally compartmentalize large heaps. They also allow monitoring of pregnant solution chemistry i. The application of internal berms was observed at Newmont's Gold Quarry Operation.

This application is shown conceptually in Figure 7. Selection of liner material may vary among pads at a given site. For example, Nerco Minerals installed several clay pads at the Candelaria Mine. More recently, the operator has constructed new pads on which mil HDPE is placed over a compacted native soil subbase. Another example of different pad construction at the same site is the Preble Mine operated by Pinson Mining Company near Winnemucca, Nevada.

Because it is desirable to have a new pad ready to put in service ready for heap construction after the winter season ends, how- ever, pads with synthetic liners are constructed in the fall.

Synthetic liners mil PVC with a protective gravel layer can survive the winter undamaged and be put in immediate service in the spring. Whereas, unloaded clay pads would be damaged by drying and winter weather if not protected by ore heaps. Also, clay cannot be worked properly in the colder weather en- countered during the period in which these pads are constructed. Because clays are available locally, however, they are the material of choice for pads constructed during the warmer months of the year.

Clays and ancient lake bottom sediments suitable with added moisture for use in heap leach pad construction are prevalent in the Western States. On a cost basis, compacted clay liners are usually preferred over synthetics and asphalt. Clay pads must be kept moist until the heap is constructed and leaching has been initiated. A clay pad that is allowed to dry will form cracks large enough for sand to blow into, and the channels so formed will not reseal themselves.

If this occurs, pregnant solution may be lost through seepage when leaching begins. Treating the surface of a clay pad with chemical polymer or emulsion surfactants will make it less permeable. The cost of a clay pad is highly dependent on the proximity of a source of suitable clay. Conceptual diagram of internal berms on a heap leach pad. Conveyors or radial stackers also can be used.

Ore is placed with a front-end loader to a maximum height of about 16 ft, pushed up with a dozer, or dumped by truck on top of the heap. Conveyors or stackers as used at Ortiz, for example convey ore to the heaps and thus avoid compaction due to equipment traffic on the ore. The slope of the sides of the heaps, which are shaped like truncated pyramids, is the natural angle of repose of the ore, typically about Heights of heaps vary from 16 ft limit of front-end loaders up to ft.

The specific ore placement technique profoundly influences the efficiency 2 of gold recovery from the heap. Care must be taken during ore placement to avoid compacting the material, which can reduce its permeability significantly. Heap height is limited by the ability of the foundation and pad to support the weight of the heap without failure, the structural stability of the ore, and its permeability. It was once thought that leaching solutions became oxygen-deficient after percolating through about 10 ft of ore, and that gold 2 extraction could be hindered.

Heaps much higher than 10 ft are now in common use, however, and achieve good recoveries. After the ore has been leached, it is either spoiled on the pad, exca- vated, and removed to a spoil-disposal area or another lift of ore is placed on top of it and leaching is continued. Ideally, when multiple lifts are leached, the leach solution will percolate through all lifts and dissolve additional metal values from the lower previously leached lifts.

Fine ores are generally leached in a single lift, whereas coarse material e. This is because fine ores are typically depleted after one leach cycle, and coarse ores generally take 2 longer to leach. The application of multiple lifts allows more efficient use of pad space. Characteristics of the particular ore and land availability dictate heap height, and the choice between multiple- and single-use pads.

Crush to -1 In. Crush to 1. Leach pad construction 12 In. CA Lincoln Co. Uncrushed mine ore Leach pad construction n. For example, Pinson Mining Company originally planned 60 individual adjacent single-lift heaps, each with a height of about 16 ft.

During construction and operation of the heaps, it was determined that two additional lifts could be placed after the top of the previously- leached material was scarified. The benefits of this multiple-lift method are additional gold recoveries from releaching lower lifts and lower pad construction costs because more ore can be treated on any given pad.

As another example, heap construction at the NERCo Minerals Candelaria Mine has involved placement of seven contiguous heaps, each about ft long, ft wide, and 20 ft high. After leaching is completed on each heap 45 to 60 days , the surface is scarified and another lift is placed on top of it. Each lift of ore is placed by truck and dozer to a height of 25 ft. The top 5 ft is then pushed off to remove any material compacted by the equipment.

The ultimate height of the heap will be ft. Another example is the Carlin-2 operation of Newmont Gold Company, where two acre pads have been constructed. Run-of-mine ore is stacked in a single lift, to a height of 50 ft. Additional lifts may be added in the future, which will result in an ultimate heap height of ft. Leach solutions basically consist of sodium cyanide, caustic i.

Antiscaling additives are sometimes used to prevent foul- ing of the sprinkler heads. Sodium cyanide, the only commercially proven lixiviant, is added to maintain a concentration in the barren solution of about 0. Caustic usual- ly lime, caustic soda, or sodium hydroxide is added to maintain the alkaline pH of the barren solution.

Most operations have a net water loss due to evaporation as much as 10 percent and require the addition of fresh water for makeup. Makeup water is typically obtained from wells installed for that purpose. Schematic flow diagram of leach solutions at a typical heap leach operation. Source: Hutchinson, Ian. Surface Water Control. Some operations may discharge treated bleed streams under NPDES permit , however, if they have a net water gain as a result of local climatic conditions.

The barren solution is sprayed onto the surface of the heap. Plastic pipes distribute the solution to impulse rainbird or wobbler-type sprinklers. These sprinklers are favored because they distribute the solution evenly and produce a large droplet, which minimizes evaporation. Sprinklers are usually placed on ft centers over the top of the heap. The typical solution o application rate is 0.

This operation is monitored to ensure that the sprinklers are functioning, that they do not become stuck in one position, and that no ponding of solution occurs on the surface. Ponding indicates the application rate is too great or that a zone of low permeability exists. In either case, efforts are made to correct the situa- tion by reducing the solution application rate or by scarifying the top of the heap.

Moisture content in run-of-mine ore varies, but levels in the 5 to 10 percent by weight range could be considered typical. Solution applied to a fresh heap percolates through the ore, flowing over ore particles and into cracks and crevices by capillary action. Sufficient solution must be applied to saturate the heap and overcome its storage capacity before any solution can drain from the heap. Storage capacity of the heap is determined by the porosity and quantity of the ore in the heap.

When saturated, the moisture content is typically in the range of 10 to 15 percent by weight. Solution equivalent to 10 percent of the weight of the ore may be required to wet the heap, and an additional 10 percent may be stored in the heap during steady- 19 state leaching.

For example, the ft-high heaps at the Pinson operation contain about 90, tons of run-of-mine ore. Initial breakthrough of solu- tion occurs about 18 hours after solution application begins application 2 rate is 0. Based on site measurements, about , gallons are required to saturate an individual heap. When heaps are idled over winter at this site and releached in the spring, the same storage capacity is noted. A small heap having 2 40, ft of surface area, for example, would generate a maximum of gallons per minute, assuming no losses 40, ft x 0.

The acre heap at Carlin's Gold Quarry Operation generates a flow of gallons per minute under steady state conditions. The chemistry of the pregnant solution differs from that of the barren spray. Concentrations of gold are measured in hundredths of an ounce per ton of pregnant solution. The pregnant solution at Round Mountain, for example, contains about 0.

The pH of the preg- nant solution is usually lower than the barren spray because of the neutrali- zation that occurs in the heap and COp pickup from the atmosphere. In the case of agglomerated ore, however, the pH of the pregnant solution may be the same or higher as that of the barren spray because of the alkalinity imparted by the cement used as the binder. The free cyanide content is also lower in the pregnant solution because some cyanide volatilizes at the surface of the heap.

Cyanide percolating through the heap is also tied up in metal complexes e. To maintain the typical 1 pound of cyanide per ton of solution concentration in the barren spray that is necessary for efficient leaching requires the addition of an amount of cyanide equal to its consumption in the heap. At the sites visited during the project, reagent usage reportedly varies from 0. Caustic in the form of lime is added to the barren liquid at a rate of 0.

The pregnant solution flows down-slope over the leach pad to a lined collection ditch. Collection ditches are situated along one or two sides of the pad, depending on the pad's slope. If the pad slopes to one side, the collection ditch is located along that side. If the pad slopes to a corner, the ditch is located along both sides joining at that corner. Collection ditches, like leach pads, are lined to prevent loss of pregnant solution.

If the leach pad is constructed with a synthetic liner, the collection ditch is lined with a continuation of the same material or a different thickness of the same material. In the case of asphalt pads, the collection ditches are continuous with the pad and are constructed of asphalt. The pregnant solution flows by gravity through the lined collection ditch to a lined surface impoundment, known as the pregnant solution pond. This impoundment is normally situated adjacent to and immediately downgrade from the heap.

The industry standard is believed to be the use of synthetic single liners placed over a compacted subbase of native soils or clays. Observation ports are installed under all leach ponds in Nevada in order to detect seepage through pond liners. Groundwater monitoring around solution ponds varies in extent and sophistication. The pregnant solution pond is the largest of the surface impoundments used in the operation because it must be able to hold not only the normal flow of pregnant solution, but also any additional flow due to normal rainfall or unusual i.

Thus, the dimensions of the pregnant solution pond are a function of the size of the heap and the climate at the site. These ponds are typically 10 to 20 ft deep and have side slopes of h:v. For instance, Candelaria's pond has a capacity of 9 million gallons and 2. Typically, an emergency overflow basin is situated immediately downgrade from the pregnant solution pond. This basin may be lined with a synthetic, as at Candelaria, or it may be constructed of native clays or unlined.

Its function is to provide emergency containment of any overtopping of the pregnant solution pond. Pregnant solution is pumped to the precious metal recovery process, where gold or silver is removed.

The barren solution is usually sent to a barren solution pond, which may be about half the size of the pregnant solu- tion pond.

Some sites e. The barren solution is treated with cyanide and caustic, as discussed previously, as it is pumped back to the heap. The heap leach system often has a total residence time of more than 3 days. Other sites have developed application methods e. The impact of winter on heap leach operations is more pro- nounced in northern climates e. Leaching operations also may be interrupted for other reasons. Some facilities may operate only intermittently to allow oxidation to occur in the heap, which permits additional gold values to be recovered.

Still others may operate in this manner because they are undercapitalized or only part-time business ventures. Uncon- ventional recovery processes, such as ion exchange, solvent extraction, and direct electrowinning, also may be applicable in special circumstances. Carbon adsorption is the method of choice at smaller operations because it costs less. The barren solution is returned to the heap. This is normally accomplished in a series of countercurrent tanks. The stripped carbon is regenerated by steam or thermal reactivation.

Zinc dust precipitation can also be used. At the majority of sites, the leach residue currently generated is left on the pads at closure.

At closure, the smallest heap would be less than an acre in size and 16 ft or less in height. Such a heap would be generated by a small-scale, short-term venture. One of the largest heaps would be 50 or more acres in size and to ft in height. A large heap such as this would have been generated by a large-scale operation that processed the ore over a period of years and added multiple lifts to the heap.

Only at those sites using reus- able pads is the leach residue removed from the pad. At these sites, the process of removing the leach residue from the pads and disposing of it is continuous over the active life of the site. Standard industry practice is to follow the leaching of an individual heap with a drainage period lasting 1 or more days, during which no solution is applied.

The heap is then rinsed with fresh water for several days. For example, the State of Nevada requires rinsing until a preset limit i. Again in Nevada, for example, no discharge of solution is permitted and the barren solution is lost to evaporation. As documented in previous reports, essentially no data are available on 21 the quantity of cyanide remaining in heap leach residue. How effective a short-term rinsing with fresh water is in removing all free cyanide from the residue has not been demonstrated.

The addition of a cyanicide such as hypochlorite to rinse water has been documented at three sites Annie Creek, Stibnite, and Darwin. Again, the effectiveness of this treatment is largely unknown. Leach residue disposal at sites that have reusable pads is accomplished by excavating the residue after it has been drained and rinsed with fresh water, loading it into trucks, and hauling it a short distance to a dump area.

The residue is end-dumped from the top of the disposal pile and cas- cades over the outer face of the pile. This spreads the residue out in a thin layer that dries rapidly.

This method of disposal was observed at both the Smoky Valley and Carlin-2 operations. Free cyanide left in the residue probably would volatilize and escape to the atmosphere. Operations of one of the larger sites visited Candelaria indicated that at closure, heaps will be rinsed as discussed earlier, and any solution remaining in the impoundments pregnant and barren ponds will be evaporated to dryness as specified in their permit. Collection ditch liners and other exposed liner material around the heap will be removed and placed in the empty impoundment.

The impoundment liner will then be folded over on itself and buried in place. After closure, the liners beneath heaps would afford little protection against leachate seepage.

Any leachate formed in the heap would flow down- ward over the liner and run off the end of the liner onto the ground. If ditch and impoundment liners were left in place, the leachate would collect in the pregnant pond, where it would evaporate or leak to the ground if the liner should fail over time.

The generation of leachate after closure is a function of the rates of precipitation and evaporation and the water reten- tion characteristics of the spoil. Additional discussion on leachate forma- tion is presented in Section 5.

In particular, pregnant and barren solution ponds are surrounded by fencing, and signs are posted to warn of the presence of cyanide. In arid areas, the presence of surface water is a strong attraction to passing animals, especially when the nearest surface water may be five or more miles away.

Operators often construct fresh water ponds at a location away from the production area to provide a drinking water source, thereby lessening the chance that animals would attempt to gain access to and drink the cyanide solutions in the pregnant or barren solution ponds or collection ditch. Flags and netting are also used to discourage birds from using solution ponds and ditches at some sites.

VALLEY LEACH Heap leaching has been conducted in areas where relatively flat native terrain was not available by constructing and grading a waste rock or over- burden fill to form the necessary surface. More recently, an approach called "valley leach" has been used for heap leaching operations in moderate to steep terrain.

Valley leach is a modification of heap leaching that is applicable in steep terrain where typical heaps cannot be constructed.

The system involves construction of a containment dike by using compacted waste rock at the downhill limit of the heap and placement of a liner over 22 the upstream face of the dike and over the pad area above it. The heap is then constructed behind the dike. The major difference between a valley leach and a typical heap leach operation is that a pregnant solution pond is not constructed in the valley leach system unless the cyanicides in the ore necessitate the use of an external pond.

The pregnant solution is stored internally in the heap in the voids of the ore and contained by the con- tainment dike and liner. A conceptual diagram of a valley leach system is shown in Figure 9. A valley leach system requires a durable ore one that will not break down upon leaching for stability.

Typical cross-section of a valley leach type heap. Source: Ref. Pregnant solution is extracted either by pumping wells or by gravity through valved pipes passing through the containment dike. A considerable data base is available on cyanides from mining operations and the environment.

Very little data are available, however, on the types or quantities of cyanides in heap leach residue. The following discussion is meant to be generic to allow the reader, especially anyone unfamiliar with the topic, to put information presented in previous sections and the conceptual controls discussed in the following section in context. This equates to about ppm. The protective alkalinity is maintained in the barren solution pond by the addition of lime, and a pH between 9 and 11 is maintained.

Under these conditions, the cyanide present is mostly free cyanide, as required in the leaching reaction. The barren solution pond typ- ically holds hundreds of thousands of gallons of this solution. The pregnant solution pond contains lesser concentrations of free cyanides because of the destruction, losses, and complexation that occur in the heap; however, a significant concentration of free cyanide is still present.

The solution in these surface impoundments represents the greatest source of free cyanide at a leach operation. Failure of the containment system, liner failure, or overtopping of the pond would result in free cyanide in an alkaline solution being released to the environment. Several metallo- cyanide complexes can occur in leach heaps. Some of these are strongly bound and stable, some are moderately bound and dissociate with time, and some other forms dissociate easily.

As the metal! Strong metal! The complexes that are formed in a given heap are determined by the mineralogy of the ore. As metal! Depend- ing on the p'H, the free cyanides can be released to the atmosphere or leached with rainwater. If the pH of the heap leach is less than 9t some or most of the free cyanide will be released to the atmosphere. If the pH is greater than 9, free cyanide will remain in solution.

Low concentrations of soluble free cyanides are amenable to biodegradation. High concentrations of free cyanide are not easily biodegraded, however, and could result in cyanide contamination in runoff or in liquids percolating to underlying soils and ground water. During gold heap leaching an alkaline pH 9 to 11 is main- tained, but afterwards the piles are usually rinsed with fresh water and the pH approaches a more neutral range; thus, much of the free cyanide can be volatilized.

Leach residue near the surface of the heap can become less alkaline with the absorption of CCL from the atmosphere. If the heap is not rinsed or rinsing is inadequate, the solution remaining in the interior of the heap may remain alkaline and be a potential source of free cyanide. Concentrations of cyanide in heap leach residue vary with the ore composi- tion, the pH of the residue, treatment of the residue i.

Ore mineralogy affects the types of complexes formed, which determines their long-term stability, as previously discussed. Few researchers have described the effects of treatments such as fresh water rinse and treatment with hypochlorite on cyanide concentrations in the heap; however, alkaline rinses, water rinses, and rinses with oxidizing agents are some of the meth- ods that may be used to increase rates of destruction of free cyanide and thus more quickly reduce the cyanide concentrations remaining in the heap leach residue.

For example, the State of Nevada requires that leach residue be rinsed with fresh water until the pH of the solution exiting the heap is 8. Few data are available on the content and fate of cyanide in heap leach residue. Available data indicate that cyanide in heap leach residue decreases over time. As part of a study on the long-term degradation of cyanide in an inactive heap, Engelhardt measured total and free cyanide concentrations at 23 various depths and locations in a heap over an month period.

It was also found that free cyanide concentrations in heap samples were only slightly less than total concentra- tions. In two other studies, Schmidt et al. Contamina- tion was limited to a depth of less than 24 inches in the soil at this site 24 where liner failure had occurred.

Several environmental factors influence the rate of degradation of cyanide in heap leach residue. Intermittent rainfall and higher temperatures are both conducive to increased release of cyanide and degradation within the heap.

Mixing of the material that occurs when leach residue is spoiled disposed of off the pad enhances cyanide degradation. As leach residues are aerated, they become more neutral and less alkaline through absorption of carbon dioxide from the atmosphere.

As the pH decreases, cyanide is in- creasingly volatilized as HCN. Effect of pH on dissociation of hydrogen cyanide. Huiatt, ed. Free cyanide in the form of HCN is the most toxic; many metal! The toxicity of metal! Those that dissociate readily to release free cyanide, such as zinc and cadmium cyanide complexes, are highly toxic. Others that exhibit moderate dissocia- tion are less toxic; these include copper and nickel cyanide complexes.

So set your clock, make stuff around your base and when the time is up take the Pebblenoses out of the compost heap. Otherwise all your invested Gold Coins will be wasted. Make sure that it also contains Ice. The Gold Dust disappears and in the bottom right corner icons should be visible with a very slow growing bar. It takes 6 hours to let the Pebblenoses grow into Rocknoses. This timer is not critical. Right after you placed everything, you can add a stack of stone, which is the resource the Rocknoses will use to produce what ever they will produce.

Do something different and come back later. After this you can repeat the process.