Prospecting for Gold

What is GOLD:
Gold is a precious metal that is 19.3 times heavier than water, has a brilliant luster, is malleable and easily formed, is a ductile transition metal with an atomic number of 79  and the elemental Symbol of "Au". Whew, what a mouthful!

Why go prospecting for gold? At prices in excess of $600.00 US per troy ounce (1/1/07) you might be able to pay for a Panning Vacation.

"GOLD" Just the mention of Gold stirs up the adventurer in most of us. Only a small fraction of the worlds gold has ever been exploited and the rest is out there just waiting to be found, refined and put to good use. Most gold exist in the form of ore and is not normally found in nuggets of any notable size. Even in panning for gold one has to realize and accept that at best all they will find may be gold dust or flakes. The dream that many novices have of finding a vein of solid gold is just that a dream. It is not that they couldn't exist it has just not proven to be the case. However huge nuggets weighing hundreds of pounds have been found but this is the exception and not the norm. Most gold that is being mined is measured in grams (not even ounces) per ton of ore. 1 gram per ton is not uncommon but how big is a gram? About the size of a grain of rice and this is only after all the grains are pushed together in one pile.

Now that we have thoroughly discouraged you, let us tell you how to  find, identify, mine (placer mining) separate and even a basic concept of how to refine GOLD.

What to look for:   This is an exceptional sample of gold bearing quartz.

First you need to be in an area that was conducive to formation of gold many millions of years ago (See geological sampling). Many of these have already been located by other enthusiast. Some went as far as to get a mineral lease on the placer and never followed thru with it or passed away and no-one bother to follow up on it. Leases and expiring leases are a shortcut to determining where you can get started. Gold nuggets are not as common as one would hope and must either be dug out of a vein where the gangue minerals may have been disintegrated and leached away, leaving the gold relatively untouched, or if you are lucky you may find a "placer" that has gold particles that became precipitated (Separated from the dissolved fluid form)  and deposited on a nuclei of gold  as they are moved along by the alluvium of streams, rivers, beaches, etc. The process is similar to a snowball getting larger as it is rolled through the snow.  This is the process that is largely responsible for the formation of nuggets in pay sand See definitions.
Be careful to not "Jump" someone else's claim or mineral lease. Some people are militantly protective of their Gold so check with your government officials to find out if the area your intend to work is already let out to someone else. In the United States you can contact the Bureau of Land Management  ( http://www.blm.gov  ). There used to be assayer's offices in just about every town in gold regions that would verify your find as gold and then issue you a claim, but it has become much more complex than that.

Identifying.
Gold has a particular luster that you would think is easily recognizable but Iron Pyrites looks so much like gold that novices will sometimes spend a great deal of time harvesting a product that is virtually worthless. However Gold is sometime intermingled with iron Pyrites so use caution before discarding pyrites. To determine if what looks like gold is in fact gold you can expose it to nitric acid. Nitric acid has long been used to confirm the presence of gold in items because it will dissolve most other material but not gold. To test a sample you scrape the "gold" across a piece of slate so as to leave a streak on the slate. Drip a drop of nitric acid on the streak and if the streak is still visible after 5 minutes then "EUREKA" you have gold.

Locating:

Panning:  
The gold panning is  by far the most common way to make your first strike, and often used to find the richest gold bearing ground (sampling), so that heavier equipment such as dredges,  and sluice boxes can be brought in to work  the most promising regions.

What you need:
A large gold pan and a small sampling pan These come in many sizes, materials and styles
A screen for your pan
Tweezers long jewelers style available where you purchase your pans or Radio Shack
A magnifying glass with a neck lanyard.
A magnet to remove Black Sand from the gold concentrate.
Small spoon scoop
A wide mouth receptacle with a flapper top on it to put your gold in and a lanyard to keep you from losing it while you are working.
Glass specimen vials.

It is important to understand the principle of alluvium deposits- The gold is eroded from an ore vein somewhere upstream and the motion of the water wears away the ore exposing the gold and carrying it downstream. Gold  is so heavy that it settles in areas where the turbulence is strong enough to remove most of the gangues but yet not great enough to continue moving the heavier gold downstream.

By panning you can work your way up stream until you find the lode or the vein that is feeding the river with gold. Note: sometimes more that one vein is contributing to the content on a long river and it is advisable to continue panning as you progress upstream and noting the yield as you go. If it  makes a significant downturn, that would indicate that you have just passed one of the contributing sources of the metal.
To begin panning your will want to locate and area in a creek , river or stream where there are classic locations for deposits to reside. By this we mean on the outside corner of a bend, an area strewn with boulders or submerged shelves (rock out-croppings) or rapids flowing into a deeper pool or even a lake. Choose a spot where the water is not too deep and moves just swiftly enough to keep the water clear. If an area pays then you can explore the deeper areas by using a dredge
Dress the part. Wear tall rubber boots and thermal socks or hip waders and long johns. The water passing around your legs will rob you of your thermal energy and make you uncomfortable and prematurely tired. Being tired makes it dangerous. You don't want to slip and fall in some remote location with no one else around to help you.

Begin panning by scooping the loose material on the downstream side of a boulder. Pour this through 1/4 inch or smaller screen into your pan (they make screens especially for gold pans) until the pan is 1/3 full (less is easier for a green horn (novice)). Look over the larger material left on top of your screen on the outside chance that you might spot a large nugget there. Remove the screen, clip it to a belt loop and look at the material that is now in your pan. Stir it with your fingers. You may find a nugget large enough to use a tweezers to pick it out (a picker). Remove the largest pebbles that don't contain gold. With your pan just under surface of the water begin swishing water around in it  with an undulating motion (a slight rotating rocking). Do this just fast enough that the lighter sediment spills over the side, while the heavier material remains in the bottom of the pan. This exact procedure may vary for pans of a different design (gravity trap style )but then they will usually come with their specific instructions. Be sure to break up any clay balls as there may be gold trapped in them. You can use a finger to stir though this sediment and look for  gold "color". If you see some then you may need to continue swishing until most of the extraneous material is washed over the side. Use caution to not attempt to discriminate so completely that you begin to lose your gold. Some materials such as "Black sand" is so dense that it is nearly impossible to separate from the gold by panning alone. That is where the magnet comes in. Black sand is comprised of iron and will be attracted to the magnet thereby leaving the gold in your pan.
Once you have the gold in a fairly concentrated form on the crease of your pan your can pinch it between your fingers and place it into you specimen receptacle or directly into your vials. Be sure to put the top on.

Metal detecting:
Great strides have been made in developing metal detectors suitable for prospecting. The largest manufacturers such as Garret, White and Minelab can help direct you to the best model for your endeavors. A few of the features that you will want is waterproof, ground balancing and discrimination. This will help to eliminate some of the false hits.
 

When you reach the location you want to work you will begin passing the detector over the ground, boulders and rock cliff faces. Even with ground balancing you will get the occasional bleep as the detector passes over uneven surfaces. This is because the induced electromagnetic field will vary along with the uneven surfaces. You will soon learn to discount these ghost signals. It is recommended that you wear headphones as this will allow you to better define the type of bleep that you are hearing.

The metal detectors transmitting coil produces a primary electromagnetic field. When passed over a conductive object  currents flow through the surface of the object, producing its own secondary electromagnetic field.  A receiving coil within the metal detector receives the distorted electromagnetic field signal. Based upon the strength of the distortion the unit gives of audio signal in the form of a series of bleeps. The size of the surface of  a conductive material that is actually facing the coil helps to determine how strong the signal is. In other words a buried knife blade laying flat on it's side would give a greater response than the same blade at the same depth buried on edge. Because gold is usually in small amounts it's presence will likely be represented in a series of small bleeps. The more gold particles in a given area the more it will sound like bleeping static. A large coil will cover more area but the smaller coils tend to give you a deeper penetration. Undoubtedly there will be other conductive material naturally present in the soil or rocks such as Iron, copper and Iron Pyrites (fools Gold). It will take some practice and a lot of false starts before one is able home in on Gold's particular bleep. Don't entirely discount all other materials, as fortunes have been made in metals other than just Gold.

 It is best to practice while at home with different materials so that you can learn to distinguish the different tone that different metals give of. This will save a lot of needless digging. Samples of different ore can be obtained from Rock collector supply hoses and geological education material suppliers.

When detecting in wilderness area such as the northwestern region of North America it is best to wear  ahead phone over just one ear so that the other ear can listen for the possibility of  Grizzlies. Make a fair amount of human noises such as whistling so that you don't surprise one, giving it time to evade you, which is their normal tendency. 

Geological sampling:

Geological sampling is the process of observing a given rock formation and than taking samples by chipping off a piece for analysis. But which rock? 

A mineral deposit is made up of ore minerals, which carry the metal, and gangue minerals, which are formed along with the ore minerals but contribute nothing to the value deposit. For example, gold veins often are made up of large amounts of quartz and carbonate gangue, with some pyrites and a little gold. 
A classic example of common gold ore    See that little speck just to the right of center?

The common way to determine where to begin your search is to avail yourself of publicly available government geological survey data.  Many  governments  employ mapping geologists, who examine large areas, making note of all pertinent geological features (See the United States Department of the Interior, and  it's bureau the United States Geological Survey). The geological reports and maps they make serve as an important source of reference. Experienced prospectors plan their search in areas where the rocks and geological structures suggest there could be mineralization. Hydrothermal alteration is a sign that fluids have passed through a rock, and is one of nature’s clearest messages that there may be a mineral deposit nearby. Geo thermally  super heated water dissolved the individual minerals millions of years ago and was precipitated  as it flowed into and was deposited by cohesion into a crack in the base rock (vein). This process was similar to hard water deposit on the inside of a kettle.

Three  things may happen to gold in primary deposits:

1. The gold and its surrounding gangues material (Often quartz and pyrites) may lay in waiting in the vein in the form of gold ore. Usually the percentage of gold to waste material is quite small in this setting.
2. The gangue minerals may be disintegrated and leached away, leaving the gold relatively untouched. In this case the gold is usually in a much higher concentration.
3. The  gold  and it gangues may be eroded either chemically or by mechanical (wind and water) erosion and deposited in placer beds.

You will need to take several samples and have them assayed to determine the financial feasibility of actually mining your claim.

Just a word about claiming a strike.
Use a GPS to determine your location. There are claim kits available in waterproof containers. You will fill out the claim form and the leave one copy at the site (posting) and the other one you take it back to civilization to have it registered. Then you will likely need a mineral lease for the area that you have determined to have pay dirt. The process varies for each country and even by states so do your homework and don't go bragging about your find until you know that it is completed. You may use an law firm that specializes in this process but make certain that you have a contract with them to perform the registration of a specific claim. Keep a copy

How to mine the gold:

Dredging

Dredging is simply using a pump capable of handling solids up to 3/4 of an inch, and sucking up the alluvial gravel from the most ideal location, just as in panning. This slurry mixture will be transported by tube to the shore or a barge for processing (See Sluice).  A diver will be in the water and at least one other person working the sluice  and another being shore support. The diver manipulates the suction hose, raking it across the gravel to stir it up so the suction stream can pull the material into the pump and then onto the sluice.

A most common error for novice prospectors to make is not doing enough sampling before setting up operations ( See Panning). Take the time to find the best paying areas before lugging all your equipment in.

This is an arduous and demanding job and requires Scuba gear or a compressor (not the same type you use to blow up tires) and hose to supply air while you man the intake end of the  suction hose. You will need to wear a wet suit so that you don't get hypothermal complications and switch off with a partner or at least take a break every hour or so.

Because most claims are in remote areas, be sure to select good equipment and take in enough supplies to last a while because going in to town to restock can be difficult at best.

Sluicing

See sluice box for a description.     Click for a larger image

Using a sluice box is real skill and must be practiced to insure that your are getting the highest return for your effort.

Basically the gold ore bearing sluice or slurry mixture is loaded into the top of the sluice. Water flowing from the top helps to move the material down the chute and over the ribs. As it flows down over the ribs the les dense and larger particles spill over the ribs and out the bottom end. An improvement to a basic sluice is the addition of the rocker box feature which permit the  box to be rocked from side to side the help dislodge the larger less dense particles from slightly curved and shortened ribs, leaving the heavier, possibly gold particles trapped in the crease of the rib. When used with a dredge, the dredge will need to shut down occasionally just to let you pull out the black sand and harvest the gold particles.

Refining

Refining placer gold is much easier than having to crush and refine gold ore from a vein. Placer ore  usually has a much higher percentage or gold and once the black sand is extracted by magnetism you should have a fairly high concentrate that can be sold to a refiner who will process it and then pay you for it. However if you want to go it yourself, pull the nuggets and flakes out of your specimens and the rest you must grind it with a solution of lime and Cyanide (Highly poisonous). This creates what is called a slurry. The slurry is the placed in a tank where the heaviest particles sink to the bottom and the lighter sludge runs out over the top. The material that settles to the bottom can be separated by centrifuge or while still in solution the gold can be extracted by electrolysis. The gold containing particles is then dumped into a vat of mercury where all less dense material floats to the surface and is skimmed off. The Mercury is the boiled  and captured in a condenser to be reused while the gold is left behind. It is more involved than this but this is the basic as it is down by the natives in places like Brazil.

Definitions of Gold related terms:

Aeolian = deposited by wind - also known as eluvial
Alluvium or alluvial deposits = deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion
Auriferous = Deposits or material containing gold in it's natural form
eluvial deposits or eluvium  or aeolian= Residual deposits of gold particles produced by the action of wind.
Black Sand = A magnetic and dense sand that has a variety of elements combined with iron, It obtains its glossy black appearance oxidation and erosion. Black sand can sometimes contain additional valuable elements. This is removed from the screenings with a magnet.
Claim = Making a legal claim on the sole right to mine minerals in a specific location.
Cohesion = the intermolecular force that holds together the molecules in a solid or liquid
Gangues = The extraneous rock material that gold is embedded in.
Iron Pyrite - Fools gold = A shiny brass colored crystalline substance.  It has isometric crystals that usually appear as cubes. The cube faces may be striated (parallel lines on crystal surface or cleavage face). Often mistaken for gold is often adhered to quartz and may have small amounts of gold hidden in it.  This is when you need your magnifying to look for striations. The crystals may vary in size from near microscopic to 3/4 of an inch.
Lode= refers to the vein that has been eroding to make the deposits in the placer. The mother lode is a great strike or find.
Placer = (sand bed) A Place where gold has been deposited by erosion. This may be in an exposed river bed or even buried (buried placers or "old" paleo placers) by volcanic, glacial or similar action. The terminology of the zone or stratum containing an economic concentration of gold in eluvial and alluvial placers is varied. The miner's term 'pay streak',  is commonly used in Canada and the United States. Other  terms in use include 'pay gravel', 'pay sand', 'pay dirt', 'pay wash', 'pay channel', 'pay lead', 'run of gold', 'gutter' and 'wash dirt'.
Precipitated = A chemical process where dissolved particles are extracted out of a solution.
Primary deposits = A vein where the dissolved or leached gold and gangue first settled and precipitated.
Sluice Box = A box contraption that is usually 9 feet or longer with 3/4 inch high ribs fastened to the inside bottom, and is mounted at an angle with a discharge for the waste at the bottom end. A combination of a sluice and a rocker box is the most efficient method.  Modern day sluice box often have "astro turf" or outdoor carpet in the bottom instead of the ribs. This can be removed and shaken over a piece of plastic sheet to dislodge any trapped particles. Normally it will require further separating (removing black sand) to get an acceptable specimen.
Strike = Striking pay dirt, finding the gold, the basis for the term "Striking it rich"

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