Gold Panning Instructions

Saturday, April 3, 2010

STEP A. WASHING OFF LARGER ROCKS AND MOSS
1. Fill pan 3/4 full of gravel, then submerge it deep enough so it is just under the surface of the water. Give the pan several vigorous shakes back and forth and from side to side, but not too vigorous

as to wash material out of the pan.

2. Change from the shaking motion to a gentle circular movement, so the material starts revolving in a circle. This process will cause most
of the dirt and clay to
dissolve and wash out of the pan. If roots and moss surface, work them over your pan with your fingers to dissolve any lumps. Pick out the larger rocks after making sure that they are washed clean.

Repeat processes 1 and 2 of step A to get the smaller rock to the surface and to cause the heavier concentrates to settle

STEP B. WASHING OFF
LIGHTER SAND AND GRAVEL
1. Hold the pan just under the water and tilt it slightly away
from you. Begin to swirl the water from side to side, with a slight forward tossing motion. Take care, but with
sufficient force to move the surface and the lighter gravel out over the edge of the pan.

2. Leveling the pan from time to time and shaking it back and forth will cause the light material to come to the surface and the gold to settle to the bottom.

Repeat process 1 and 2 of step B until there is only about two cups of heavier material left in your pan. This material is usually called "black sand," or "concentrate."



STEP C. WASHING OFF BLACK SAND AND CONCENTRATES
At this point it is better for the beginner to raise the pan completely out of the water, leaving about an inch of water in it. Tilt the pan slightly towards you and swirl the water slowly in a circular motion to check the pan for nuggets and pieces that are easily picked out by hand.

Then submerge the pan again in water and repeat process 1 and 2 of step B for final concentration. This is the most critical part of panning. Make sure this final process is accomplished with as much diligence as possible so you do not to wash out the gold.

If you have a plastic pan, the use of a magnet can be employed to quickly aid in the separation of gold from the black magnetic sand concentrate.

Apply the magnet to the bottom side of the pan and move it in a small circular motion with the pan slightly tilted. This will swiftly isolate the gold from the black sand.

PANNING HINTS
When using a steel pan, make sure to remove all the oil from the pan before you use it. The most common way is to "burn" it over the coals of a campfire using extreme caution. The pan is heated to a dull red glow, then dunked in water. This not only removes the oil but also gives the pan a dark blue hue, which makes the gold easier to see. If any oil is left in the pan, it will cause the fine gold to float, making separation impossible.

Another secret to speed up the final steps is to keep a small squeeze bottle of detergent close at hand. A couple of drops in the pan during the last separation will break the surface tension of the water and speed up the operation considerably.
In conclusion, don't let anyone tell you that this country's rivers and streams no longer contain gold. Every year winter storms bring more to the surface, continually renewing nature's supply. It's all there for the taking, and the gold pan is still the best way to find it!

An item that is considered a necessary part of a panners equipment is a panning sieve. The sieve sets over the pan and can screen or classify the larger cobbles, making the panning process much easier. The sieves are available in sizes from 1/4 of an inch (4-mesh) to a 100-mesh size screen. The gold pan sieves are most popular with the medium size pan and are available in most prospecting stores that sell gold recovery equipment.

Read more...

Gold Prospecting & Panning | Gold Mining & Metallurgy


We are going to show you the basic theory and methodology you need to find where gold is present, how to identify it and what alternatives there are for the extraction of gold via panning or other. In short, this site will show you everything you need to know about gold prospecting. Although we'll explain to great extend the "how to" of searching for mineral deposits within ore veins, this guide considers free gold ( Gold Placers of various types ) as the main source of this precious metal. Also learn how to invest in gold via our other detailed guide.

Mining extraction and metallurgy of gold has been pursued with great interest since it developed intrinsic value as a result of its economic and physical properties, its decorative appeal and its scarcity. During much time gold has been the most attractive metal on the world, and still to this day is one the ones most fever and many developments and new ideas have appeared as a consequence of its huge value as an economic metal.

The gold mining industry has grown considerably, and it appeared to the writer that the present would be a propitious time to bring out some guides in order to understand gold prospecting and gold mining. What has been goal of the site is to make "Prospecting for Gold" a compendium, in especially concrete form, of useful information respecting the processes of winning from the soil and the after- treatment of gold and gold ores, including some original suggestions. Practical information, original and selected, mining jobs are given to mining company directors, mine managers, mill operators, and prospectors. In each part, will be found a large number of useful hints on subjects directly and indirectly connected with the gold mining.

All the information should be very useful and surely is original, and each reader will be able to understand the difficult task of processing gold ores found in the veins that bear it. You'll learn the art of extracting valuable metals from gravel placers.

Here, you can learn about metal detecting as well as gold panning. You get to learn why gold placers will form where they form. You'll learn how to look and how to find gold placers (that's prospecting!) and analyze it.

Those unfamiliar with prospecting and mining will find a great Glossary of the Mining Trade's Terms. The characteristics of an ore deposit and its minerals assemblages (mineralization) determine mining methods, extraction process (recovery methods & equipment needed), and the performance of all chemical processes involved in gold extraction. Thus, a good knowledge of an ore is required to develop a gold extraction and the efficiency of the process.





The gold mineralogy can offer the following variations:

Read more...

Gold Minerals


Gold does not react at ambient temperature and pressures and consequently there are very few naturally occurring compounds of the metal. The average concentration of gold in the world is about 0.005 g/t, that is lower than other metals. The low concentration of gold in primary rocks means that upgrading by a factor of 3000-4000 is usually required during ore formation processes to achieve commercial concentrations. This may be possible natural gravity concentration processes or leaching gold with natural fluids from the host rock. Thus, by highly oxidizing, acidic and complexing (chloride) solutions, followed by redeposition in a more concentrate form. Owing to its siderophile properties (weak affinity for oxygen and sulfur, high affinity for metals) gold tends to concentrate in residual hydrothermal fluids and subsequent metallic or sulphidic phases, rather than silicates, which form at an early stage of magma cooling. Rocks that are high in clays and low in carbonates are the best sources of gold, and reprecipitation occurs when the hydrothermal solutions encounter a reducing environment, such as a region of high carbonate, carbon or reducing sulphide contain.

The predominant occurrence of gold is as native metal, often alloyed with up to 15 % silver. Other gold minerals include alloys with tellurium, selenium bismuth, mercury, copper, iron, rhodium and platinum. Therefore gold occurs in a mineral form different to most other elements.



Gold Mining & Gold Prospecting Gold Gold Prospecting and Mineral Deposit Exploration History of Gold Gold Minerals Rocks that are Rounded, Subrounded and Subangular How Rocks are formed Basic Mineralogy Native Gold Electrum Gold tellurides Other gold minerals. Main Types of Placers Obtaining Mining Permits and why they are Necessary Occupations in the Mining Industry The Diverse Uses of Gold Geological Agents The Properties of Minerals Geology of Streams Mining Terminology Classifications of gold -bearing materials Special Gold Deposits Exploration Methods Prospecting Gold How to Find Gold Finding Gold Gold Panning Gold Mining Equipment Gold Extraction Methods - Metallurgy Gold Smelting & Refining - Metallurgy Mine-Prospecting Dictionary Process Flowsheets Investing in Gold Contact e-Gold Prospecting & Mining Gold Mining Exploration Gold Prospecting and Mineral Deposit Exploration How to Find Gold Nuggets Hot Rocks & the Problems They Cause Where to Find Gold

Read more...

Conversion of Gold Ore to Gold Metal

Thursday, April 1, 2010





Conversion of Gold Ore to Gold Metal
Adapted from: PAMP (Produits Artistiques de Métaux Précieux), a gold, silver and platinum group metals refinery based at Castel San Pietro, in Switzerland
http://www.pamp.com/gold_c/Info_site/in_glos/in_
glos_heapleaching.html




Heap Leaching

The successful application of heap leaching to the extraction of gold from low-grade deposits has been one of the main factors in higher output since the 1970s, especially in the United States. It is a low cost process that extracts a soluble precious metal or copper compound by dissolving the metal content from the crushed ore.

Ore is heaped onto open-air leach pads with a base of asphalt or impervious plastic sheeting. A sprinkler system is then laid along the top of the ore pile through which a solution of dilute cyanide is sprayed. The cyanide percolates down through the heap for several weeks, leaching out the gold. This solution, now enriched with gold, drains off the bottom of the pad into what is known as the "pregnant pond", from which it is pumped to the recovery plant.

It should be noted that cyanide is extremely toxic and must be handled with special care.

Heap leaching of gold was pioneered in the United States in 1973 at Placer Development's Cortez open pit in Nevada and proved on a larger scale at Pegasus Gold's Zortman Landusky mine in Montana. Although it is low cost, recovery rates average only sixty to seventy per cent, significantly less than with conventional milling. But it has enabled low-grade ores, which otherwise might not be economically viable, to be processed. In the United States, where heap leaching is used most extensively, half of all production is won by this method.

Cyanide/Cyanidation

Cyanide ions have a natural affinity for gold, which reacts with the gold solid particles to make gold cyanide complexes which are soluble in water. Cyanidation has been the principal method of extracting gold from ore since the development of the MacArthur-Forrest Process in 1887, which proved crucial in the development of the South African gold mining industry.

The perfection of the cyanide process largely replaced amalgamation with mercury that had previously been the main method of extracting gold from ore. Cyanidation has also become crucial since 1970 in gold recovery from low grade deposits through heap leaching. It should be noted that cyanide is extremely toxic and must be handled with special care.

In the MacArthur Forrest Process the ore is crushed to a fine powder and circulated through tanks containing a weak solution of cyanide, which has form tetracyano gold complexes. The complexation reaction results in dissolving the gold and the remaining rock pulp is filtered off. Zinc dust added to the cyanide solution to chemically reduce the gold oxidation state from III to zero. The gold is now in the metal element state with zero charge and appears as fine specks of gold to be precipitated out and the precipitate is then refined.




Spraying cyanide on leach padsat the Zortman-Landusky mine
in Montana (Credit: Timothy Green)


Heap Leaching: extraction of gold using heap leaching and carbon recovery

Read more...

Placer mining

Tuesday, March 30, 2010

Panning

Gold panning is mostly a manual technique of sorting gold. Wide, shallow pans are filled with sand and gravel that may contain gold. The pan is submerged in water and shaken, sorting the gold from the gravel and other material. As gold is much denser than rock, it quickly settles to the bottom of thepan. The panning material is usually removed from stream beds, often at the inside turn in the stream, or resting on the bedrock bed of the stream, where the density of gold allows it to concentrate. This type of gold found in streams or dry streams are called placer deposits.



Gold panning is the easiest technique for searching for gold, but is not commercially viable for extracting gold from large deposits, except where labor costs are very low and/or gold traces are very substantial. It is often marketed as a tourist attraction on former goldfields. Before production methods can be used, a new source must be identified. Panning is a good way to identify placer gold deposits so that they may be evaluated for commercial viability


Metal detecting

With a metal detector, a person may walk around an area and systematically scan below the surface. The sensor can give a positive reading for a quantity of gold to a depth of as much as a meter below the surface. As the device is easy to operate and highly mobile, this method of prospecting is very popular among gold miners

Sluicing
Using a sluice box to extract gold from placer deposits has been a common practice in prospecting and small-scale mining throughout history to the modern day. A sluice box is essentially a man-made channel with riffles set in the bottom. The riffles are designed to create dead zones in the current to allow gold to drop out of suspension. The box is placed in the stream to channel water flow. Gold-bearing material is placed at the top of the box. The material is carried by the current through the box where gold and other dense material settles out behind the riffles. Less dense material flows out of the box as tailings.
Larger commercial placer mining operations employ screening plants, or trommels, to remove the larger alluvial materials, such as boulders and gravel, before concentrating the remainder in a sluice box or jig plant. These operations typically include diesel-powered, earth-moving equipment, including excavators, bulldozers, wheel loaders and rock trucks.













Dredging
Although this method has largely been replaced by modern methods, some dredging is done by small-scale miners using suction dredges. These are small machines that float on the water and are usually operated by one or two people. A suction dredge consists of a sluice box supported by pontoons, attached to a suction hose which is controlled by the miner working beneath the water.

State dredging permits in many of the United States gold-dredging areas specify a seasonal time period and area closures to avoid conflicts between dredgers and the spawning time of fish populations. Some states, such as Montana, require an extensive permitting procedure, including permits from the U. S. Corps of Engineers, the Montana Department of Environmental Quality, and the local county water-quality boards.

Some large suction dredges (100 hp+ 10 inch) are used in commercial production throughout the world. Small suction dredges are much more efficient at extracting smaller gold than the old "bucket line" was. This has improved the chances of finding gold. Smaller dredges with 2 to 4-inch (100 mm) suction tubes are used to sample areas behind boulders and along potential pay streaks, until "color" (gold) appears.
Other larger scale dredging operations take place on exposed river gravel bars at seasonal low water. These operations typically use a land-based excavator to feed a gravel-screening plant and sluicebox floating in a temporary pond. The pond is excavated in the gravel bar and filled from the natural water table. "Pay" gravel is excavated from the front face of the pond and processed through the floating plant, with the gold trapped in the onboard sluicebox and tailings stacked behind the plant, steadily filling in the back of the pond as the operation moves forward. This type of gold mining is characterized by its low cost, as each rock is moved only once. It also has low environmental impact, as no stripping of vegetation or overburden is necessary, and all process water is fully recycled. Such operations are typical on New Zealand's South Island and in the Klondike region of Canada


Hardrockmining
Hard rock gold mining is done when the gold is encased in rock, rather than found as particles in loose sediment. Hard rock mining produces most of the world's gold. Sometimes open-pit mining is used, such as at the Ft. Knox Mine in central Alaska. Barrick Gold Corporation has one of the largest open-pit gold mines in North America, located on its Goldstrike property in northeastern Nevada. Other gold mines use underground mining, where the ore is extracted through tunnels or shafts. South Africa has the world's deepest hard-rock mine, which mines gold from as deep as 3900 meters under the ground.

Byproduct gold mining
Gold is also produced by mining in which it is not the principal product. Large copper mines, such as the Bingham Canyon mine in Utah, often recover considerable amounts of gold and other metals along with the copper. Some sand and gravel pits, such as those around Denver, Colorado, may recover small amounts of gold in their washing operations. The largest-producing gold mine in the world, the Grasberg mine in Papua, Indonesia, is primarily a copper mine.

Gold ore processing
In placer mines, the gold is recovered by gravity separation. For hardrock mining, other methods are usually used.

Cyanide process
Main article: Gold cyanidation
Cyanide extraction of gold may be used in areas where fine-gold bearing rocks are found. Sodium cyanide solution is mixed with finely-ground rock that is proven to contain gold and/or silver, and is then separated from the ground rock as gold cyanide and/or silver cyanide solution. Zinc is added to the solution, precipitating out residual zinc, as well as the desirable silver and gold metals. The zinc is removed with sulfuric acid, leaving a silver and/or gold sludge that is generally smelted into an ingot then shipped to a metals refinery for final processing into 99.9999% pure metals.

Advancements in the 1970s have seen activated carbon used in extracting gold from the leach solution. The gold is absorbed into the porous matrix of the carbon. Activated carbon has so much internal surface area,[1] that fifteen grams (half an ounce) has the equivalent surface area of the Melbourne Cricket Ground (18,100 square meters). The gold can be removed from the carbon by using a strong solution of caustic soda and cyanide. This is known as elution. Gold is then plated out onto steel wool through electrowinning. Gold specific resins can also be used in place of activated carbon, or where selective separation of gold from copper or other dissolved metals is required.

The cyanide technique is very simple and straightforward to apply and a popular method for low-grade gold and silver ore processing. Like most industrial chemical processes, there are potential environmental hazards presented with this extraction method in addition to the high toxicity presented by the cyanide itself. This was seen in the environmental disaster in Central-Eastern Europe in year 2000, when during the night of 30 January, a dam at a goldmine reprocessing facility in Romania released approximately 100,000 m³ of wastewater contaminated with heavy metal sludge and up to 120 tons of cyanide into the rivers of Tisza.

Cradle
A cradle was rocked back and forth while water was poured over it. The sand and gravel was washed through the screen of the cradle, leaving the gold behind.

Read more...

Read more...

Extracting gold from rock



Information on how to extract gold from rock, one of the scientists' challenges on the BBC/OU series Rough Science 3




The Challenge
Unlike alluvial gold, which is found as very small flakes on river banks, gold-bearing rocks have to be dug out of the ground. We want pure gold, but gold-bearing rocks include lots of other materials such as quartz, calcite and the sulfides of other metals. We need to separate the gold from everything else in the rock so the rock needs to be treated in some way.

In New Zealand we chiselled some rocks from an outcrop near a small creek. We were pretty sure our rocks contained some gold as there were disused gold mines dating back from the 1870s close by.

Crushing the rock
Crushing the gold bearing rock is not as simple as it sounds. We can't just hit it with a hammer because pieces will fly everywhere and we may lose some of our gold. What we need is a very strong container and bash plate. That way, we can crush the rock without losing any of the precious gold particles.

We also need a special kind of hammer, which fits into the container without leaving too much room for the rock to escape. Rather than use a conventional hammer, we used pulleys and a rope to raise and drop a heavy weight. Pulleys increase the length of rope that needs to be pulled in order to raise the heavy weight but at the same time they reduce resistance. If we use a two-pulley system we will have to pull the rope twice as far as if we had one pulley or no pulleys at all, but we will be able to lift twice as much weight. This would be useful because, for the same effort, we can use twice the weight to crush our rocks.


Powdering the rock
The next step was to take the crushed pieces of rock and make them even smaller. We used a heavy metal rod (a broken half shaft from a four wheel drive) and smashed the small bits of rock in a saucepan. The rock needed to be powdered for us to get to all the gold within the rock. This is a time-consuming job because we needed a very fine powder - far finer than even sand. We wore out several pairs of gloves in the process.

Mercury
We used mercury to get the gold out of the powdered rock. Gold, like most minerals, can be 'dissolved' in mercury to form what's called an amalgam. An amalgam is a physical mixture, a type of alloy. This is a comparatively straightforward way of separating the gold from the rock, as the rock remains untouched by the mercury.

However, the use of mercury is very hazardous and mercury pollution in South American rivers following recent gold rushes has poisoned many indigenous inhabitants of the Amazon rainforest as well as the environment.

But how could we get our hands on some mercury?

Where could we find mercury?
The most common ore of mercury is called cinnabar. Its scientific name is mercury sulfide (HgS). In its pure man-made form it's called vermillion, a pigment much valued by painters. Luckily, we were given a huge chunk of cinnabar for this challenge - even though there are large deposits of cinnabar in New Zealand, there were none where we were based. Unfortunately, the cinnabar we were given was of a pretty low grade. But needs must and we had to use it. In some cinnabar ores, where the mercury sulfide concentration is high, you can actually see small beads of metallic mercury in the ore. It certainly wasn't the case with our cinnabar, unfortunately.

It theory at least all we needed to do was grind the cinnabar to a fine powder, and heat it gently, whereupon the mercury sulfide readily decomposes, producing mercury vapour (and sulfur). The mercury vapour can be condensed on the walls of a cold test tube as metallic beads, making them quite easy to collect.

The amalgamation
So how do you use mercury to extract the gold from gold-bearing rock? When you mix the finely powdered gold-bearing rock with some mercury, the gold within the rock dissolves, to form what's called a gold amalgam.

The next step in the process is to separate the gold amalgam from any 'unreacted' mercury. We did this by squeezing the crude amalgam through a small piece of chamois leather. Shiny metallic beads of mercury oozed through the leather, leaving the gold amalgam behind.

Baked potatoes
We now had some gold amalgam, but the challenge was to obtain gold, not some weird alloy. So how do you recover the gold from the amalgam?

Believe it or not, that's where a potato comes in handy. Mercury has a melting temperature well below that of gold, and, when gold amalgam is heated gently, it decomposes to give mercury vapour and purified gold. The flesh of the potato absorbs the mercury vapour, preventing its escape into the atmosphere.

It sounds absurd, but our resident alchemist, Mikey B got it to work. The gold that we got this way looked a bit black and bitty, but it was definitely gold. I don't know how efficient the process was, but we probably got a couple of grams of gold from several large sacks of our gold-bearing rock. And all it took was a lot of crushing and a bit of chemistry wizardry.

Read more...

  © Blogger template On The Road by Ourblogtemplates.com 2009

Back to TOP