Introduction

Metal detectors are fascinating machines! Many people who use them are just as enthusiastic about discussing the virtues of their favorite metal detector as they are about setting off in search of buried treasure. Those who design and build these instruments for a living listen carefully when one of thier customers talks about his or her experience in the field, because this is the primary means by which we determine how well we are doing our jobs, and what sort of things we need to do better. Sometimes though, communication is difficult. Almost as though we and our customers speak different languages. Which in a sense, we do. The purpose of this page is to try to narrow that communication gap a little. And, to resolve some of that “typical curiosity” metal detector operators have regarding what is going on inside their instruments.

Is it necessary to know how a metal detector works in order to use it effectively? Absolutely not. Will knowing how it works help someone to use it more effectively in the future? Quite possibly yes, but only with persistence and practice. The best metal detector available is still only as good as the person using it.

VLF (Very Low Frequency) Transmitter & Receiver

Transmitter

Inside the metal detector’s loop (sometimes called a search head, coil, antenna, etc.) is a coil of wire called the transmit coil. Electronic current is driven through the coil to create an electromagnetic field. The direction of the current flow is reversed several thousand times every second; the transmit frequency “operating frequency” refers to the number of times per second that the current flow goes from clockwise to counterclockwise and back to clockwise again.

When the current flows in a given direction, a magnetic field is produced whose polarity (like the north and south poles of a magnet) points into the ground; when the current flow is reversed, the field’s polarity points out of the ground. Any metallic (or other electrically conductive) object which happens to be nearby will have a flow of current induced inside of it by the influence of the changing magnetic field, in much the same way that an electric generator produces electricity by moving a coil of wire inside a fixed magnetic field. This current flow inside a metal object in turn produces its own magnetic field, with a polarity that tends to be pointed opposite to the transmit field.

Receiver

A second coil of wire inside the loop, the receive coil, is arranged (by a variety of methods) so that nearly all of the current that would ordinarily flow in it due to the influence of the transmitted field is cancelled out. Therefore, the field produced by the currents flowing in the nearby metal object will cause currents to flow in the receive coil which may be amplified and processed by the metal detector’s electronics without being swamped by currents resulting from the much stronger transmitted field.

The resulting received signal will usually appear delayed when compared to the transmitted signal. This delay is due to the tendency of conductors to impede the flow of current (resistance) and to impede changes in the flow of current (inductance). We call this apparent delay “phase shift”. The largest phase shift will occur for metal objects which are primarily inductive; large, thick objects made from excellent conductors like gold, silver, and copper. Smaller phase shifts are typical for objects which are primarily resistive; smaller, thinner objects, or those composed of less conductive materials.

Some materials which conduct poorly or not at all can also cause a strong signal to be picked up by the receiver. We call these materials “ferromagnetic”. Ferromagnetic substances tend to become magnetized when placed in a field like a paper clip which becomes temporarily magnetized when picked up with a bar magnet. The received signal shows little if any phase shift. Most soils and sands contain small grains of iron-bearing minerals which causes them to appear largely ferromagnetic to the metal detector. Cast iron (square nails) and steel objects (bottle caps) exhibit both electrical and ferromagnetic properties.

It should be pointed out that this discussion describes an “Induction Balance” metal detector, sometimes referred to as “VLF” Very Low Frequency (below 30kHz). This is the most popular technology at the present time, and includes the “LF” Low Frequency (30 to 300kHz) instruments made for prospecting.

Discrimination

Since the signal received from any given metal object exhibits its own characteristic phase shift, it is possible to classify different types of objects and distinguish between them. For example, a silver dime causes a much larger phase shift than an aluminum pull-tab does, so a metal detector can be set to sound off on a dime yet remain quiet on the pull-tab, and/or show the identification of the target on a display or meter. This process of distinguishing between metal targets is called “discrimination”. The simplest form of discrimination allows a metal detector to respond with an audio output when passed over a target whose phase shift exceeds a certain (usually adjustable) amount. Unfortunately, with this type of discriminator the instrument will not respond to some coins and most jewelry if the discrimination is adjusted high enough to reject common aluminum trash for example pull-tabs and screw-caps.

A more useful scheme is what is called “Notch Discrimination”. With this type of system, a notch in the discriminate response allows the metal detector to respond to targets within a certain range (such as the nickel/ring range) while still rejecting targets above that range (pull-tabs, screw-caps) as well as below it (iron, foil). The more sophisticated notch metal detectors allow for each of several ranges to be set for either accept or reject responses. White’s Spectrum XLT for example, provides 191 individually programmable notches.

A metal detector may provide a numeric readout, meter indication, or other display mechanism which shows the target’s likely identity. We refer to this feature as a Visual Discrimination Indicator, or V.D.I. Metal Detectors with this capability have the advantage of allowing the operator to make informed decisions about which targets they choose to dig rather than relying solely on the instruments audio discriminator to do all the work. Most, if not all, V.D.I. metal detectors are also equipped with audio discriminators.

Metal detectors can distinguish metal objects from each other based on the ratio of their inductance to their resistivity. This ratio gives rise to a predictable delay in the receive signal at a given frequency. An electronic circuit called a phase demodulator can measure this delay. In order to separate two signals, such as the ground component and the target component of the receive signal, as well as to determine the likely identity of the target, we use two such phase demodulators whose peak response is separated from each other by one fourth of the transmitter period, or ninety degrees. We call these two channels “X” and “Y”. A third demodulated signal, we call “G”, can be adjusted so that its response to any signal with a fixed phase relationship to the transmitter (such as the ground) can be reduced to zero regardless of the strength of the signal.

Some metal detectors use a microprocessor to monitor these three channels, determine the targets’s likely identity, and assigning it a number based on the ratio of the “X” and “Y” readings, whenever the “G” reading exceeds a predetermined value. We can find this ratio with a resolution of better than 500 to 1 over the full range from ferrite to pure silver. Iron targets are orientation sensitive; therefore as the loop is moved above them, the calculated numerical value may change dramatically. A graphic display showing this numerical value on the horizontal axis and the strength of the signal on the vertical axis is extremely useful in distinguishing trash from more valuable objects. We call this display the “SignaGraph” (TM).

Ground Balance

As previously mentioned, most sands and soils contain some amount of iron. They may also have conductive properties due to the presence of salts dissolved in the ground water. The result is that a signal is received by the metal detector due to the ground itself which may be thousands of times stronger than the signal resulting from small metal objects buried at modest depths. Fortunately, the phase shift caused by the ground tends to remain fairly constant over a limited area. It is possible to arrange things inside the metal detector so that even if the strength of the ground signal changes dramatically–such as when the loop is raised and lowered, or when it passes over a mound or hole–the metal detector’s output remains constant. Such a metal detector is said to be “ground balanced”. Accurate ground balance makes it possible to “pinpoint” the location of the targets with a good deal of precision as well as to estimate the depth of the targets in the ground. If you choose to search in a non-discriminate, or “all-metal” mode, accurate ground balance is essential.

The simplest form of ground balance consists of a control knob which the operator adjusts while raising and lowering the loop until good balance is achieved. Although this method can be quite effective, it can also be tedious, and some people find it to be difficult or confusing. More advanced metal detectors will perform ground balance automatically, typically by a two-step sequence in which the metal detector is balanced with the loop raised, then balanced once more with the loop lowered to the ground. The most sophisticated ground balance metal detectors will gradually adjust themselves as changes in the composition of the ground occur. We refer to this as “Tracking Ground Balance”. A good tracking metal detector allows you to balance once, then hunt for the rest of the day without having to balance again. A word to the wise – many metal detectors which are advertised as having “automatic” or “Tracking” ground balance are actually factory preset to a fixed balance point. Its a little like welding your car’s accelerator halfway to the floor and calling it “cruise control”.

Motion/Non-Motion Modes

Athough the ground signal may be much stronger than the target signal, the ground signal tends to remain the same, or change very slowly, as the loop is moved. The signal from the target, on the other hand, will rise quickly to a peak and then subside when the loop is swept over it. This opens up the possibility of using techniques to separate ground from target signals by looking at the rate of change of the receive signal rather than looking at the receive signal itself. Metal detector modes of operation which rely on this principle are called, not surprisingly, “Motion” modes. The most important example is a mode called “Motion Discrimination”. If we wish to isolate the target signal well enough to determine the target’s identity, the ground balance alone is not enough. We need to look at the target from a couple of different perspectives, sort of like the way distances can by measured by triangulation if you have more than one viewpoint. We can only be ground balanced from one particular “viewpoint”; the other will contain some combination of target and ground signal. Fortunately, we can use the motion technique to minimize the effect of the remaining ground signal. At the present time, all discriminating and V.D.I. metal detectors require loop motion to be effective. This turns out not to be much of a penalty in practice since you have to move the loop anyway in order to cover any ground.

Once you have located a target in the motion discrimination mode, you will probably want to more precisely locate it for easy recovery. If your metal detector is equipped with a depth meter, you will also want to measure the target’s depth. “Pinpoint” locating and depth measurement are done in what is called the “All Metal” mode. Since discrimination is not required to perform these functions, loop motion is not usually required — except for that motion required to get the loop over the center of the target. More precisely, the speed at which you move the loop is not important. The All Metal mode (also sometimes called the “Normal” mode, or “D.C.” mode) is therefore called a “Non Motion” mode.

There are a few potential points of confusion here. Some metal detectors are equipped with a feature called “Self Adjusting Threshold”, or S.A.T., which gradually increases or decreases the audio output in an attempt to maintain a quiet but audible “threshold” sound. This helps to smooth out audio changes caused by the ground or inadequate ground balance. S.A.T. may be very rapid or very slow depending on the metal detector and how it’s adjusted, but strictly speaking, S.A.T. implies a motion mode of operation. This is why you will hear certain metal detectors referred to as having a “True Non Motion” mode; meaning, of course, an All Metal mode without S.A.T. Another sometimes confusing thing is that some discriminators allow for adjustment down to the point that the discriminator responds to all metals — in other words, it’s a discriminator that doesn’t discriminate. This is something very different, however, than the All Metal mode previously described. For this reason we often refer to it as a “Zero Disc” mode.

Microprocessor Control

The microprocessor is a complex electronic circuit which can perform all of the logic, arithmetic, and control functions necessary to build a computer. A sequence of stored instructions called a “Program” is performed by the microprocessor, one at a time, at a speed which can be as high as several million times every second.

The use of microprocessors in modern metal detectors has opened up possibilities which were undreamed of just a few years ago. In the past, adding new and useful features to a metal detector meant additional control knobs and switches. There were obvious limits to this approach; at some point size, cost, and operator confusion got out of hand. With a microprocessor, a liquid crystal display, and a simple keypad the problem is solved. A virtually unlimited number of features can be added without adding any additional hardware. These features can be arranged by a system of “Menus”, so that anybody who can follow the prompts on the display can easily find the control they’re after and adjust it to their liking. In this way, a single metal detector can be set up for just about any application, or to suit anyone’s personal preference.

You might think that this sounds a little complicated — what if you don’t want to be bothered with making all of those adjustments? Here’s the real beauty of microprocessor control; you don’t have to. Each control can be set to a typically useful position by the microprocessor each time you turn the machine on so the beginner or casual user never has to know that all those advanced features are there. Or better yet, you can select your preference from the menu — coin hunting, prospecting, relic hunting, etc. — and the microprocessor will make all of the adjustments for you choosing settings that have been proven in actual use by seasoned veterans.

In addition to these advantages, powerful software routines can be used to enhance the metal detector’s audio discrimination capabilities and to display information in a variety of formats on an L.C.D. making the operator’s job of interpreting target responses faster and easier.

VLF Summary

Although the modern high performance VLF metal detector has been several decades in the making, new advances will continue to be made. Better, smarter, easier-to-use machines will eventually be introduced. Today’s very best metal detectors will not be easy to improve on but as long as there is treasure to be found, you can be sure that research is underway to take metal detecting technology to the next level.

P.I. (Pulse Induction)

Transmitter

The search coil or loop of a Pulse Induction metal detector is very simple when compared to a VLF instrument. A single coil of wire is commonly used for both the transmit and receive functions.

The transmitter circuitry consists of a simple electronic switch which briefly connects this coil across the battery in the metal detector. The resistance of the coil is very low, which allows a current of several amperes to flow in the coil. Even though the current is high, the actual time it flows is very brief. Pulse Induction metal detectors switch on a pulse of transmit current, then shut off, then switch on another transmit pulse. The duty cycle, the time the transmit current is on with reference to the time it is off, is typically about 4%. This prevents the transmitter and coil from overheating and reduces the drain on the battery.

The pulse repetition rate (transmit frequency) of a typical PI is about 100 pulses per second. Models have been produced from a low of 22 pulses per second to a high of several thousand pulses per second. Lower frequencies usually mean greater transmit power. The transmit current flows for a much longer time per pulse however, there are fewer pulses per second. Higher frequencies usually mean a shorter transmit pulse and less power however, there are more transmit pulses per second.

Lower frequencies tend to achieve greater depth and greater sensitivity to items made from silver however, less sensitive to nickel, and gold alloys. They typically have a very slow target response which requires a very slow coil sweep speed.

Higher frequencies are more sensitive to nickel and gold alloys however, less sensitive to silver. They may not penetrate quite as deep as the lower frequency models regarding silver however, can be used with a faster coil sweep speed. Higher frequency models are generally more productive for treasure hunting because the faster sweep speed allows more area to be searched in a given time, and they are more sensitive to the ultimate beach find, gold jewelry.

As previously mentioned a typical PI search loop contains a single coil of wire which serves as both the transmit and receive coil. The transmitter operates in a manner similar to an automobile ignition system. Each time a pulse of current is switched into the transmit coil it generates a magnetic field. As the current pulse shuts off, the magnetic field around the coil suddenly collapses. When this happens, a voltage spike of a high intensity and opposite polarity appears across the coil. This voltage spike is called a counter electromotive force, or counter emf. In an automobile it is the high voltage that fires the spark plug. The spike is much lower in intensity in a PI metal detector, usually about 100 to 130 volts in peak amplitude. It is very narrow in duration, usually less than 30 millionths of a second. In a PI metal detector it is called the reflected pulse.

Receiver

Resistance is placed across the search coil to control the time it takes the reflected pulse todecay to zero. If no resistance, or very high resistance is used, it will cause the reflected pulse to “ring”. The result is similar to dropping a rubber ball onto a hard surface, it will bounce several times before returning to rest. If a low resistance is used the decay time will increase and cause the reflected pulse to widen. It is similar to dropping a rubber ball onto a pillow. Since we are interested in having it bounce once critical damping for a rubber ball might be like dropping it onto carpet. A PI coil is said to be critically damped when the reflected pulse decays quickly to zero without ringing. An over or under dampened coil will cause instability and or mask the fast conducting metals such as gold as well as reduce detection depth.

When a metal object nears the loop it will store some of the energy from the reflected pulse and will increase the time it takes for the pulse to decay to zero. The change in the width of the reflected pulse is measured to signal the presents of a metal target.

In order to detect a metal object we need to concern ourselves with the portion of the reflected pulse where it decays to zero. The transmit coil is coupled to the receiver through a resister and a diode clipping circuit. The diodes limit the amount of transmit coil voltage reaching the receiver to less than one volt so as not to overload it. The signal from the receiver contains both the transmit pulse and the reflected pulse. The receiver has a typical gain of 60 decibels. This means the area where the reflected pulse reaches zero is amplified 1,000 times.

Sampling Circuit

The amplified signal coming from the receiver is connected to a switching circuit which samples the reflected portion of the pulse as it reaches zero. The reflected pulse up to this point references in actuality a series of pulses at the transmit frequency. When a metal object nears the coil the transmit portion of the signal will remain unchanged while the reflected portion of the pulse will become wider. The metal object stores some of the electrical energy from the transmit pulse and increases the time it takes for the reflected pulse to reach zero. An increase in duration of a few millionths of a second is enough to allow the detection of a metal target. The reflected pulse is sampled with an electronic switch controlled by a series of pulses which are synchronized with the transmitter.

The most sensitive sampling point on the reflected pulse is as near as possible to the point where it reaches zero. This is typically about 20 millionths of a second after the transmitter shuts off and the reflected pulse begins. Unfortunately, this is also the area where a PI can become unstable. For this reason most PI models sample the reflected pulse at a decay of 30 or 40 millionths of a second, well after it decays to zero.

Integrator

In order for an object to be detected the sample signals must be converted to a DC voltage. This task is performed by a circuit called an integrator. It averages the sampled pulses over time to provide a reference voltage. This DC reference voltage increases when metal nears the coil, then decreases as the object moves away. The DC voltage is amplified and controls the audio output circuitry which increases in pitch and/or volume to signal the presents of metal.

The time constant of the integrator determines how quickly the metal detector will respond to a metal object. A long time constant (in the range of seconds) has the advantage of reducing noise and making the metal detector easier to tune. Long time constants require a very slow sweep of the coil because a target might be missed if it passes quickly by the search coil. Short time constants (in the range of tenths of a second) respond more quickly to targets. This allows a quicker sweep of the loop however, it also allows more noise and instability.

Discrimination

PI metal detectors are not capable of the same degree of discrimination as VLF metal detectors.

By increasing the time period between transmitter shut-off and the sampling point (pulse delay), certain metal items can be rejected. Aluminum foil will be the first to be rejected followed by nickel, pull tabs and gold. Some coins can be rejected at very long sample delays however, iron cannot be rejected.

There have been many attempts to design a PI that can reject iron however these attempts have had limited results. Iron is detectable at very long time delays however, silver and copper have similar characteristics. Such long time delays also have a negative affect on detection depth. Ground mineralization will cause some widening of the reflected pulse as well, changing the point at which a target responds or rejects. If the time delay is adjusted so that a gold ring doesn’t respond in an air test, that same ring may respond in mineralized ground. Mineralized ground thus changes everything regarding the time delays and discrimination of PI metal detectors.

Ground Balance

Ground balancing, while very critical on VLF metal detectors, is not necessary with PI circuits. Average ground mineralization will not store any appreciable amount of energy from the search coil and will not usually produce a signal. Such ground will not mask the signal from a buried object. On the contrary, ground mineralization will add slightly to the duration of the reflected pulse increasing the depth of detection. The term “automatic ground balance” is often applied to PI instruments because it will normally not react to mineralization and there are no external adjustments for any specific ground conditions.

Heavy black sand is an exception. It will cause a VLF coil to overload, making metal detector penetration poor at best. A PI detector will work in black sand however, some false signals may result if the coil is held very close to the ground. Ground responses can be minimized by using a longer time delay between the shut-off and sample point (pulse delay). Advancing the time delay slightly will help to smooth out the noises caused by most mineralization.

Automatic vs. Manual Tuning

Most PI detectors are manually tuned. This means the operator has to adjust a control until a clicking or buzzing sound is heard in the headphones. If the search conditions change, such as when moving from black sand to neutral sand or from dry land to salt water, the tuning must be re-adjusted. Failure to do so can result in reduced detection depth and missed targets. Manual tuning is very difficult with short integration time constants, so most manually tuned models use long time constants and the search coil must be swept slowly.

This is not a problem when a PI is used for scuba diving because the coil cannot be swept quickly underwater. When used at the surf line, where the coil will be in and out of salt water, a manually tuned metal detector can be very frustrating to use. The tuner must be adjusted continually to maintain a threshold. Some operators elect to set it slightly below the threshold however, that can result in a reduction in depth as the ground conditions change.

Automatic tuning, or S.A.T. (Self Adjusting Threshold) offers a significant advantage when searching in and out of salt water or over mineralized ground. S.A.T. helps keep the metal detector operating at maximum sensitivity without requiring constant adjustments by the operator. It improves the stability, reduces noise, and allows higher gain settings to be used. PI metal detectors do not emit strong, negative signals like a VLF. As such they do not “overshoot” on pockets of mineralization. With S.A.T. the coil must be kept in motion while detecting a target. Stopping over a target will cause the S.A.T. to tune it out or cease responding.

Audio Circuits

PI audio circuits generally fall into two categories: variable pitch and variable volume. Variable pitch or V.C.O. (Voltage Controlled Oscillator) audio has the advantage for faint targets because the change in pitch is easier to hear than a change in volume at lower aud io levels. This is primarily true for manually tuned models. The “fire siren” sounds can become annoying and many have trouble hearing the higher tones. A variant of this is the mechanical vibrator device primarily used for deep water. It emits a slow clicking sound and vibration that increases to a buzz to signal a find. The mechanical device is easier to hear and feel over the sound of an underwater air supply.

Many people prefer a more conventional audio tone that increases in volume rather than pitch to signal a find. This audio system works best with a PI metal detector that has a fast target response and automatic tuning (S.A.T.). Automatic tuning makes the PI sound and respond similar to a typical VLF metal detector.

PulseInduction Summary

Pulse Induction metal detectors are specialized instruments. They are generally not suitable for coin hunting urban areas because they do not have the ability to identify or reject ferrous (iron) trash. They can be used for relic hunting in rural areas where iron trash is not present in large quantities, or is desired. They are intended for maximum depth under extreme search conditions such as salt water beaches and highly mineralized ground. In such conditions PI type metal detectors produce superior results when compared to VLF models, particularly in the ability to ignore such extreme ground and penetrate it for maximum depth.

2 inch – backpack dredge

.5-2 cubic-yd/hr

PROS: Light and easy to pack in and out of the location. Good for prospecting and sampling. With suction nozzle it can be used in very shallow water.

CONS: Can’t move much material so dredging is harder to do if you want to move a lot of sand and gravel. Not good for production.

3 inch – Sampling dredge

1-3 cubic-yd/hr

PROS: Still lighter and smaller than a 4 inch and can move a lot more material than the 2 inch.

CONS: Still low on production for a serious operation. Portability is pretty good for remote places.

4 inch – Sampling/small scale production dredge

1-4 cubic-yd/hr

PROS: The smallest of the production dredges but still good at sampling for pay streaks.

CONS: A bit harder to lug around, it is heavier and more work to put together and take apart. Fairly mobile still, this makes it good for more remote sites.

5 inch – larger scale sampling/production dredge

2-10 cubic-yd/hr

PROS: Good for larger operations and can move more material than all the other smaller dredges. Still good for sampling but on a bigger scale. Hose is flexible and can be operated by a single dredger.

CONS: Heavier to disassemble and move around. May have multiple or larger engines.

6 inch – a good dredge for the serious prospector/smaller commercial production dredge

6-15 cubic-yd/hr

PROS: A useful size for someone who has found a sizable pay streak and wants to get all the gold out that you can. You can move rocks gravel and sand up to about 5 inches across  without a plug up of the hose or jet.

CONS: Larger nozzle makes it harder to sample with, although you still can sample larger rivers to locate gold in bigger areas. This hose isn’t as flexible as a smaller dredge although one person can handle it well enough for production.  Two man teams are better because the rocks are uncovered so quickly by a 6″ unit that a single dredger can be overwhelmed with the work of clearing of large cobbles and small boulders that don’t fit in the suction nozzle. Can have multiple engines or engines in the 15-20 Hp range. This is a heavier machine to haul. Be ready for 2 or more assistants.

8 inch – a commercial dredge designed to process large amounts of sand, gravel and rock

10-30 cubic-yd/hr

PROS: For commercial operations this is a good size. It can suck up quite a lot of rocks, gravel and sand and in a short period of time.

CONS: For the recreational prospector looking for the fun of the outdoors and the reward of finding gold, this is not the right size. It is typically used for commercial projects. Manning the hose and moving the rocks that an 8″ dredge will need pulled out of the dredge hole require at least two men to make productive use. Dredges this size and above are generally limited in which waters they can be used.

10 to 12 inch – definitely a commercial dredge

20-50 cubic-yd/hr

PROS: Good for larger commercial operations. Moves a huge volume of sand, gravel & rocks allowing for greater volume of material that may contain gold. In a word, “VOLUME!”

CONS: Commercial dredge only. A lot of work to keep running and to move around. Lot’s of rocks to move which requires a team of underwater worker = $$.  Dredge and platform are huge and requires significant equipment (like a 80hp VW engine!) and constant big time maintenance.

CASPER, WYOMING

Here is a brief summary of GPS products:

Handheld GPS models put highly accurate navigation features in the palm of your hand. The handheld would be the most durable of the product lines and allow you to get off the beaten path. Disclaimer – Prospectinggear.com personally have the Garmin 60CSx.

Automobile GPS models mount either on the windshield or dashboard and keep you posted on the streets, highways and roads ahead. Many can guide you to your destination with voice instructions and detailed maps. Disclaimer – Prospectinggear.com personally have the Garmin 1390T.

Marine GPS chart plotters map your location on the local lake or in the farthest reaches of the ocean. Disclaimer – Prospectinggear.com personally have the Hummingbird 581i.

GPS for next generation phones or laptops can transform your iPhone, Andriod, or laptop into a completely functional GPS device.

Mapping software allows you to add voice commands, street or topo mapping, and route mapping to specific addresses.

Click HERE to view a GPS buying guide offering more in-depth data on GPS systems.

Is it real gold?

If what you found was glittering right on the floor with out digging down you probably might have mica, pyrite, or some other type of disappointing “fool’s gold”.

Listed below are some quick assessments to test when you find your ”gold”.

Solar Check – After you have seen your first Gold you will always remember it. A fast and easy test is to take a glance and note the color and brightness of the material in your gold pan. Next move your hand over the pan to create a shadow over the material. Anything that isn’t Gold will grow to be dull or fade. Gold will retain its colour and luster – it will still be golden, just Gold within the shade.

All that glitters isn’t gold, in fact probably not! Take a glance at the material in the daylight if it’s all a glitter it is a 99.999 chance it is not gold.

Pin test – Stick a pin within the “gold”. If it breaks or fractures or crumbles it isn’t gold. Gold is malleable and ductile meaning you presumably can bend it and dent it. Lesser minerals will crack, break or crumble.

Pan check – One of the first lessons to learn about gold is it is REALLY heavy. Gold will not move around in your pan much. After panning the material down to your final cons, rock your pan forwards and backwards with a little bit bit of water in the pan. You can see that the gold really hold in one place and pretty much keep put, whereas different lighter weight material will move away. As the light material moves, tap your pan lightly on the highest edge. This will separate the heavy gold even further from the waste.

Think about the location and the source of the material. In case you found your “gold” on top of the soil, it most likely isn’t real gold since gold is heavy and would have sunk through the ground. Gold is extremely heavy and can at all times seek the lowest place to rest – usually above bedrock or other dense material such as clay or limestone.

Consider buying one of those practice panning bags (we do not have experience nor recommend any particular vendor, although we have heard good things about Felix’s Pay Dirt). Having quality material will help your panning skills so you know how the gold will move and sit in the pan. Plus, you can do all of your practicing in a controlled and warm environment. Use catch pans to see if you lose any material. Once you see the real deal you’ll always be able to recognize it again.

This last year I was dredging on one of my favorite local rivers near another prospector running a much larger dredge.  We chatted over lunch and compared our sluices to see who was on the gold.  While my box had lots of fines that were starting to pile up, his dredge was practically void of any color.  He was completely dumbfounded because he had just finished telling me he was in the gold so thick!  He and I both initially thought that something was up with his dredge and recovery, but when I looked underwater, it became clear he was seeing the mica on the top of the float sand and hadn’t gone down over 1 foot since he thought he was simply vacuming up the gold on top.  The gold was actually along the bedrock 4 feet below where he was working and his recovery improved dramatically once he stopped messing with the fool’s gold.

Don’t be discouraged, keep looking – discovering your first few flakes will ignite your gold fever!

A mining claim provides the holder the right to mine on federal land, while a patent provides him outright possession of mineral-wealthy land that belongs to the federal government.

Federal lands can be determined from looking and studying maps, or talking with the various government agencies, however there aren’t any maps representing mining claims.

A mining claim could be situated on lands which are open to mineral location. In case you have a particular piece of land in thoughts and no active claims are proven on the county’s records, the land could then be open for staking.

Here is a very good eBook put out by the Bureau of Land Management (BLM) that can explain how the process works in more detail.

The “Welcome Stranger” is the largest alluvial gold nugget ever discovered, which had a calculated refined weight of 2,283 oz.6 dwts 9 gr. It measured 61 cm (24 inches) by 31 cm (12.2 inches), and was found by Cornish prospectors John Deason and Richard Oates on 5 February 1869 at Moliagul, Victoria, Australia, about 9 miles north-west of Dunolly.

 Whereas the gold from the Welcome Stranger is still out there, the nugget itself not exists. The nugget was quickly melted down and the gold was sent as ingots to Melbourne for forwarding to the Bank of England. It left Australia on board the steamship “Reigate”. Smelting produced 2268 ounces, 10 dwt 14 grains of gold.

The Holtermann Nugget discovered at Hill End, New South Whales, Australia in 1872, at 290 kg. was enormous, and certainly stays the biggest single mass of gold ever discovered, but it will probably is not considered a nugget, more of load gold. We could go into discussing rock vs placer, but the essence is that a gold nugget has left the lode sooner or later and is now not in the host rock. The Holtermann was what the Aussies name “reef gold” after the quartz reefs sought after by the laborious rock miners.

The biggest gold nugget presently in existance is the Hand of Faith on display at the Golden Nugget Casino in Las Vegas, Nevada. Found in 1980 by a person named Kevin Hillier with a metal detector near his trailer near close to Wedderburn, Victoria, Australia. The make/model of his detector is not known, however the story goes he acquired a sign, but thought his detector was acting up, so virtually did not dig! My guess is he was pretty happy he did when pulled out the 876 troy ounce (27.2 kilograms, sixty one pounds eleven ounces) Hand of Faith at about 6 inches. He later sold it to the Golden Nugget Casino for a cool million dollars!

There was one other biggie nugget over 2,200 troy ounces back in 1858 known as the “Welcome Nugget” (comparable, but minus the stranger) and a lot of other big lots and laborious rock deposits, however the Welcome Stranger remains to be the largest nugget ever discovered, and the Hand of Faith the biggest nonetheless around today.

Gold formed the basis for the gold standard used before the collapse of the Bretton Woods system. The ISO currency code of gold bullion is XAU.

Modern industrial uses include dentistry and electronics, where gold has traditionally found use because of its good resistance to oxidative corrosion.

Chemically, gold is a transition metal and can form trivalent and univalent cations upon solvation but is attacked by chlorine, fluorine, aqua regia and cyanide. Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Gold is insoluble in nitric acid, which will dissolve silver and base metals, and this is the basis of the gold refining technique known as “inquartation and parting”. Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term “acid test,” referring to a gold standard test for genuine value.

Characteristics

Gold is the most malleable and ductile metal; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square feet. Gold leaf can be beaten thin enough to become translucent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red.

Gold readily creates alloys with many other metals. These alloys can be produced to increase the hardness or to create exotic colors (see below). Gold is a good conductor of heat and electricity, and is not affected by air and most reagents. Heat, moisture, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; conversely, halogens will chemically alter gold, and aqua regia dissolves it via formation of the chloraurate ion.

Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated out as gold metal by adding any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate.

Recent research undertaken by Sir Frank Reith of the Australian National University shows that microbes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.

High quality pure metallic gold is tasteless; in keeping with its resistance to corrosion (it is metal ions which confer taste to metals).

In addition, gold is very dense, a cubic meter weighing 19300 kg. By comparison, the density of lead is 11340 kg/m³, and the second densest element, iridium, is 22650 kg/m³.

Color of gold

The usual grey color of metals depends on their “electron sea” that is capable of absorbing and re-emitting photons over a wide range of frequencies. Gold reacts differently, depending on subtle relativistic effects that affect the orbitals around gold atoms.

Applications

In various countries, gold is used as a standard for monetary exchange, in coinage and in jewelry. Pure gold is too soft for ordinary use and is typically hardened by alloying with copper or other base metals. The gold content of gold alloys is measured in carats (k), pure gold being designated as 24k.

Gold coins intended for circulation from 1526 into the 1930s were typically a standard 22k alloy called crown gold, for hardness. Modern collector/investment bullion coins (which do not require good mechanical wear properties) are typically 24k, although the American Gold Eagle and British gold sovereign continue to be made at 22k, on historical tradition. The Canadian Gold Maple Leaf coin contains the highest purity gold of any popular bullion coin, at 99.999% (.99999 fine). Several other 99.99% pure gold coins are currently available, including Australia’s Gold Kangaroos (first appearing in 1986 as the Australian Gold Nugget, with the kangaroo theme appearing in 1989), the several coins of the Australian Lunar Calendar series, and the Austrian Philharmonic. In 2006, the U.S. Mint began production of the American Buffalo gold bullion coin also at 99.99% purity.

Today, gold has fallen out of favor for use in coins made for general circulation.

Jewelry

Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color. Eighteen carat gold containing 25% copper is found in antique and Russian jewellery and has a distinct, though not dominant, copper cast, creating rose gold. Fourteen carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminium, although rarely done except in specialized jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry. Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. White gold alloys can be made with palladium or nickel. White 18 carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silver in appearance. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals (World Gold Council), but the palladium alloys are more expensive than those using nickel. High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects.

Other

* In medieval times, gold was often seen as beneficial for the health, in the belief that something that rare and beautiful could not be anything but healthy. Even some modern esotericists and forms of alternative medicine assign metallic gold a healing power. Some gold salts do have anti-inflammatory properties and are used as pharmaceuticals in the treatment of arthritis and other similar conditions. However, only salts and radioisotopes of gold are of pharmacological value, as elemental (metallic) gold is inert to all chemicals it encounters inside the body.
* Gold leaf, flake or dust is used on and in some gourmet foodstuffs, notably sweets and drinks as decorative ingredient. Gold flake was used by the nobility in Medieval Europe as a decoration in foodstuffs and drinks, in the form of leaf, flakes or dust, either to demonstrate the host’s wealth or in the belief that something that valuable and rare must be beneficial for one’s health.
* Gold solder is used for joining the components of gold jewelry by high-temperature hard soldering or brazing. If the work is to be of hallmarking quality, gold solder must match the carat weight of the work, and alloy formulas are manufactured in most industry-standard carat weights to color match yellow and white gold. Gold solder is usually made in at least three melting-point ranges referred to as Easy, Medium and Hard. By using the hard, high-melting point solder first, followed by solders with progressively lower melting points, goldsmiths can assemble complex items with several separate soldered joints.
* Gold can be used in food and has the E Number 175. Goldwasser (German: “Goldwater”) is a traditional herbal liqueur produced in Gda?sk, Poland, and Schwabach, Germany, and contains flakes of gold leaf. There are also some expensive (~$1000) cocktails which contain flakes of gold leaf[citation needed]. However, since metallic gold is inert to all body chemistry, it adds no taste nor has it any other nutritional effect and leaves the body unaltered.
* Dentistry. Gold alloys are used in restorative dentistry, especially in tooth restorations, such as crowns and permanent bridges. The gold alloys’ slight malleability facilitates the creation of a superior molar mating surface with other teeth and produces results that are generally more satisfactory than those produced by the creation of porcelain crowns. The use of gold crowns in more prominent teeth such as incisors is favored in some cultures and discouraged in others.
* Gold can be made into thread and used in embroidery.
* Gold is ductile and malleable, meaning it can be drawn into very thin wire and can be beaten into very thin sheets known as gold leaf.
* Gold produces a deep, intense red color when used as a coloring agent in cranberry glass.
* In photography, Gold toners are used to shift the color of silver bromide black and white prints towards brown or blue tones, or to increase their stability. Used on sepia-toned prints, gold toners produce red tones. Kodak publish formulas for several types of gold toners, which use gold as the chloride (Kodak, 2006).
* Electronics. The concentration of free electrons in gold metal is 5.90×1022 cm-3. Gold is highly conductive to electricity, and has been used for electrical wiring in some high energy applications (silver is even more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the Manhattan Project’s atomic experiments, but large high current silver wires were used in the calutron isotope separator magnets in the project.
* Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments (including resistance to non-chlorinated acids) has led to its widespread industrial use in the electronic era as a thin layer coating electrical connectors of all kinds, thereby ensuring good connection. For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and USB cables. The benefit of using gold over other connector metals such as tin in these applications, is highly debated. Gold connectors are often criticized by audio-visual experts as unnecessary for most consumers and seen as simply a marketing ploy. However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain computers, communications equipment, spacecraft, jet aircraft engines) remains very common, and is unlikely to be replaced in the near future by any other metal.
* Besides sliding electrical contacts, gold is also used in electrical contacts because of its resistance to corrosion, electrical conductivity, ductility and lack of toxicity.[4] Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts.
* Colloidal gold (Colloidal sols of gold nanoparticles) in water are intensely red-colored, and can be made with tightly-controlled particle sizes up to a few tens of nm across by reduction of gold chloride with citrate or ascorbate ions. Colloidal gold is used in research applications in medicine, biology and materials science. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells (Faulk and Taylor 1979). In ultrathin sections of tissues viewed by electron microscopy, the immunogold labels appear as extremely dense round spots at the position of the antigen (Roth et al. 1980). Colloidal gold is also the form of gold used as gold paint on ceramics prior to firing.
* Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. The coating, which is usually applied by sputtering with an argon plasma, has a triple role in this application. Gold’s very high electrical conductivity drains electrical charge to earth, and its very high density provides stopping power for electrons in the SEM’s electron beam, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases the spatial resolution of the image. Gold also produces a high output of secondary electrons when irradiated by an electron beam, and these low-energy electrons are the most commonly-used signal source used in the scanning electron microscope.
* Many competitions, and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner.
* As gold is a good reflector of electromagnetic radiation such as infrared and visible light as well as radio waves, it is used for the protective coatings on many artificial satellites, in infrared protective faceplates in thermal protection suits and astronauts’ helmets and in electronic warfare planes like the EA-6B Prowler.
* Gold is used as the reflective layer on some high-end CDs.
* The isotope gold-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.
* Automobiles may use gold for heat insulation. McLaren uses gold foil in the engine compartment of its F1 model.

Gold chemical compounds

Gold is attacked by and dissolves in alkaline solutions of potassium or sodium cyanide, and gold cyanide is the electrolyte used in commercial electroplating of gold onto base metals and electroforming. Gold chloride (chloroauric acid) solutions are used to make colloidal gold by reduction with citrate or ascorbate ions. Gold chloride and gold oxide are used to make highly-valued cranberry or red-colored glass, which, like colloidal gold sols, contains evenly-sized spherical gold nanoparticles.

History

The symbol for the Sun has been used since ancient times to represent gold.  Gold has been known and highly-valued since prehistoric times. It may have been the first metal used by humans and was valued for ornamentation and rituals. Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was “more plentiful than dirt” in Egypt.[7] Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. The earliest known map is known as the Turin papyrus and shows the plan of a gold mine in Nubia together with indications of the local geology. The primitive working methods are described by Strabo and included fire-setting. Large mines also occurred across the Red Sea in what is now Saudi Arabia.

The legend of the golden fleece may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah) and is included with the gifts of the magi in the first chapters of Matthew New Testament. The Book of Revelation 21:21 describes the city of New Jerusalem as having streets “made of pure gold, clear as crystal”. The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world’s earliest coinage in Lydia between 643 and 630 BC.

The Romans developed new methods for extracting gold on a large scale using hydraulic mining methods, especially in Spain from 25 BC onwards and in Romania from 150 AD onwards. One of their largest mines was at Las Medulas in León (Spain), where seven long aqueducts enabled them to sluice most of a large alluvial deposit. The mines at Ro?ia Montan? in Transylvania were also very large, and until very recently, still mined by opencast methods. They also exploited smaller deposits in Wales, such as placer and hard-rock deposits at Dolaucothi. The various methods they used are well described by Pliny the Elder in his encyclopedia Naturalis Historia written towards the end of the first century AD.

The Mali Empire in Africa was famed throughout the old world for its large amounts of gold. Mansa Musa, ruler of the empire (1312–1337) became famous throughout the old world for his great hajj to Mecca in 1324. When he passed through Cairo in July of 1324, he was reportedly accompanied by a camel train that included thousands of people and nearly a hundred camels. He gave away so much gold that it took over a decade for the economy across North Africa to recover, due to the rapid inflation that it initiated. A contemporary Arab historian remarked;

“ Gold was at a high price in Egypt until they came in that year. The mithqal did not go below 25 dirhams and was generally above, but from that time its value fell and it cheapened in price and has remained cheap till now. The mithqal does not exceed 22 dirhams or less. This has been the state of affairs for about twelve years until this day by reason of the large amount of gold which they brought into Egypt and spent there [...] ”
—Chihab Al-Umari

The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in Central America, Peru, and Colombia.

Although the price of some platinum group metals can be much higher, gold has long been considered the most desirable of precious metals, and its value has been used as the standard for many currencies (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties. Gold as a sign of wealth and prestige was made fun of by Thomas More in his treatise Utopia. On that imaginary island, gold is so abundant that it is used to make chains for slaves, tableware and lavatory-seats. When ambassadors from other countries arrive, dressed in ostentatious gold jewels and badges, the Utopians mistake them for menial servants, paying homage instead to the most modestly-dressed of their party.

There is an age-old tradition of biting gold in order to test its authenticity. Although this is certainly not a professional way of examining gold, the bite test should score the gold because gold is considered a soft metal according to the Mohs’ scale of mineral hardness. The purer the gold the easier it should be to mark it. Painted lead can cheat this test because lead is softer than gold (and may invite a small risk of lead poisoning if sufficient lead is absorbed by the biting).
This 156 ounce (4,42 kg) nugget was found by an individual prospector in the Southern California Desert using a metal detector.

Gold in antiquity was relatively easy to obtain geologically; however, 75% of all gold ever produced has been extracted since 1910. It has been estimated that all the gold in the world that has ever been refined would form a single cube 20 m (66 ft) on a side (equivalent to 8000 m³).

One main goal of the alchemists was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called the philosopher’s stone. Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today’s chemistry. Their symbol for gold was the circle with a point at its center (?), which was also the astrological symbol,and the ancient Chinese character for the Sun. For modern creation of artificial gold by neutron capture, see gold synthesis.

During the 19th century, gold rushes occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at the Reed Gold Mine near Georgeville, North Carolina in 1803. The first major gold strike in the United States occurred in a small north Georgia town called Dahlonega. Further gold rushes occurred in California, Colorado, Otago, Australia, Witwatersrand, Black Hills, and Klondike.

Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another.

Occurrence

In nature, gold most often occurs in its native state (that is, as a metal), though usually alloyed with silver. Native gold contains usually eight to ten percent silver, but often much more — alloys with a silver content over 20% are called electrum. As the amount of silver increases, the color becomes whiter and the specific gravity becomes lower.

Ores bearing native gold consist of grains or microscopic particles of metallic gold embedded in rock, often in association with veins of quartz or sulfide minerals like pyrite. These are called “lode” deposits. Native gold is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits (called placer deposits). Such free gold is always richer at the surface of gold-bearing veins owing to the oxidation of accompanying minerals followed by weathering, and washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets.

Gold minerals

Gold usually occurs in nature as the native element or as the gold silver alloy electrum. Gold does occur combined with tellurium as the minerals calaverite, krennerite, nagyagite, petzite and sylvanite. Gold also occurs as the rare bismuthide maldonite (Au2Bi) and the antimonide aurostibite (AuSb2). Gold also occurs as rare alloys with copper, lead, and mercury: the minerals auricupride (Cu3Au), novodneprite (AuPb3) and weishanite ((Au,Ag)3 Hg2).

Production

Economic gold extraction can be achieved from ore grades as little as 0.5 g/1000 kg (0.5 parts per million, ppm) on average in large easily mined deposits. Typical ore grades in open-pit mines are 1–5 g/1000 kg (1–5 ppm), ore grades in underground or hard rock mines are usually at least 3 g/1000 kg (3 ppm). Since ore grades of 30 g/1000 kg (30 ppm) are usually needed before gold is visible to the naked eye, in most gold mines the gold is invisible.

Since the 1880s, South Africa has been the source for a large proportion of the world’s gold supply, with about 50% of all gold ever produced having come from South Africa. Production in 1970 accounted for 79% of the world supply, producing about 1,000 tonnes. However by 2007 production was just 272 tonnes. This sharp decline was due to the increasing difficulty of extraction, changing economic factors affecting the industry, and tightened safety auditing. In 2007 China (with 276 tonnes) overtook South Africa as the world’s largest gold producer, the first time since 1905 that South Africa has not been the largest.

The city of Johannesburg located in South Africa was founded as a result of the Witwatersrand Gold Rush which resulted in the discovery of some of the largest gold deposits the world has ever seen. Gold fields located within the basin in the Free State and Gauteng provinces are extensive in strike and dip requiring some of the world’s deepest mines, with the Savuka and TauTona mines being currently the world’s deepest gold mine at 3,777 m. The Second Boer War of 1899–1901 between the British Empire and the Afrikaner Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa.

Other major producers are United States, Australia, China, Russia and Peru. Mines in South Dakota and Nevada supply two-thirds of gold used in the United States. In South America, the controversial project Pascua Lama aims at exploitation of rich fields in the high mountains of Atacama Desert, at the border between Chile and Argentina. Today about one-quarter of the world gold output is estimated to originate from artisanal or small scale mining.

After initial production, gold is often subsequently refined industrially by the Wohlwill process or the Miller process. Other methods of assaying and purifying smaller amounts of gold include parting and inquartation as well as cuppelation, or refining methods based on the dissolution of gold in aqua regia.

The world’s oceans hold a vast amount of gold, but in very low concentrations (perhaps 1–2 parts per 10 billion). A number of people have claimed to be able to economically recover gold from sea water, but so far they have all been either mistaken or crooks. Reverend Prescott Jernegan ran a gold-from-seawater swindle in America in the 1890s. A British fraud ran the same scam in England in the early 1900s.

Fritz Haber (the German inventor of the Haber process) attempted commercial extraction of gold from sea water in an effort to help pay Germany’s reparations following the First World War. Unfortunately, his assessment of the concentration of gold in sea water was unduly high, probably due to sample contamination. The effort produced little gold and cost the German government far more than the commercial value of the gold recovered. No commercially viable mechanism for performing gold extraction from sea water has yet been identified. Gold synthesis is not economically viable and is unlikely to become so in the foreseeable future.

The average gold mining and extraction costs are $238 per troy ounce but these can vary widely depending on mining type and ore quality. In 2001, global mine production amounted to 2,604 tonnes, or 67% of total gold demand in that year. At the end of 2006, it was estimated that all the gold ever mined totaled 158,000 tonnes.

At current consumption rates, the supply of gold is believed to last 45 years.

Price

Like other precious metals, gold is measured by troy weight and by grams. When it is alloyed with other metals the term carat or karat is used to indicate the amount of gold present, with 24 karats being pure gold and lower ratings proportionally less. The purity of a gold bar can also be expressed as a decimal figure ranging from 0 to 1, known as the millesimal fineness, such as 0.995 being very pure.

The price of gold is determined on the open market, but a procedure known as the Gold Fixing in London, originating in September 1919, provides a daily benchmark figure to the industry. The afternoon fixing appeared in 1968 to fix a price when US markets are open.

Historically gold was used to back currency; in an economic system known as the gold standard, a certain weight of gold was given the name of a unit of currency. For a long period, the United States government set the value of the US dollar so that one troy ounce was equal to $20.67 ($664.56/kg), but in 1934 the dollar was revalued to $35.00 per troy ounce ($1125.27/kg). By 1961 it was becoming hard to maintain this price, and a pool of US and European banks agreed to manipulate the market to prevent further currency devaluation against increased gold demand.

On March 17, 1968, economic circumstances caused the collapse of the gold pool, and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. Central banks still hold historical gold reserves as a store of value although the level has generally been declining. The largest gold depository in the world is that of the U.S. Federal Reserve Bank in New York, which holds about 3%[citation needed] of the gold ever mined, as does the similarly-laden U.S. Bullion Depository at Fort Knox.

In 2005 the World Gold Council estimated total global gold supply to be 3,859 tonnes and demand to be 3,754 tonnes, giving a surplus of 105 tonnes.

Price records

Since 1968 the price of gold on the open market has ranged widely, from a high of $850/oz ($27,300/kg) on January 21, 1980, to a low of $252.90/oz ($8,131/kg) on June 21, 1999 (London Gold Fixing). The 1980 high was not overtaken until January 3, 2008 when a new maximum of $865.35 per troy ounce was set (a.m. London Gold Fixing). The current record price was set on March 17, 2008 at $1023.50 (am. London Gold Fixing).

Long term price trends

Since April 2001 the gold price has more than tripled in value against the US dollar (as seen here), prompting speculation that this long secular bear market (or the Great Commodities Depression) has ended and a bull market has returned. In March 2008, the gold price increased above $1000, which in real terms is still well below the $850/oz. peak on January 21, 1980. Indexed for inflation, the 1980 high would equate to a price of around $2400 in 2007 US dollars. In the last century, major economic crises (such as the Great Depression, World War II, the first and second oil crisis) lowered the Dow/Gold ratio (which is inherently inflation adjusted) substantially, in most cases to a value well below 4 (as seen here). During these difficult times, investors tried to preserve their assets by investing in precious metals, most notably gold and silver.

Compounds

Although gold is a noble metal, it forms many and diverse compounds. The oxidation state of gold in its compound ranges from ?1 to +5 but Au(I) and Au(III) dominate. Gold(I), referred to as the aurous ion, is the most common oxidation state with “soft” ligands such as thioethers, thiolates, and tertiary phosphines. Au(I) compounds are typically linear. A good example is Au(CN)2?, which is the soluble form of gold encountered in mining. Curiously, aurous complexes of water are rare. The binary gold halides, such as AuCl, form zig-zag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives.

Gold(III) (“auric”) is a common oxidation state and is illustrated by gold(III) chloride, AuCl3. Its derivative is chloroauric acid, HAuCl4, which forms when Au dissolves in aqua regia. Au(III) complexes, like other d8 compounds, are typically square planar.

Less common oxidation states: Au(-I), Au(II), and Au(V)

Compounds containing the Au? anion are called aurides. Caesium auride, CsAu which crystallizes in the caesium chloride motif. Other aurides include those of Rb+, K+, and tetramethylammonium (CH3)4N+. Gold(II) compounds are usually diamagnetic with Au-Au bonds such as [Au(CH2)2P(C6H5)2]2Cl2. A noteworthy, legitimate Au(II) complex contains xenon as a ligand, [AuXe4](Sb2F11)2. Gold pentafluoride is the sole example of Au(V), the highest verified oxidation state.

Some gold compounds exhibit aurophilic bonding, which describes the tendency of gold ions to interact at distances that are too long to be a conventional Au-Au bond but shorter that van der Waals bonding. The interaction is estimated to be comparable in strength to that of a hydrogen bond.

Mixed valence compounds

Well-defined cluster compounds are numerous. In such cases, gold has a fractional oxidation state. A representative example is the octahedral species {Au(P(C6H5)3)}62+. Gold chalcogenides, e.g. “AuS” feature equal amounts of Au(I) and Au(III).

Isotopes

Gold has only one stable isotope, 197Au, which is also its only naturally-occurring isotope. 36 radioisotopes have been synthesized ranging in atomic mass from 169 to 205. The most stable of these is 195Au with a half-life of 186.1 days. 195Au is also the only isotope to decay by electron capture. The least stable is 171Au, which decays by proton emission with a half-life of 30 µs. Most of gold’s radioisotopes with atomic masses below 197 decay by some combination of proton emission, ? decay, and ?+ decay. The exceptions are 195Au, which decays by electron capture, and 196Au, which has a minor ?- decay decay path. All of gold’s radioisotopes with atomic masses above 197 decay by ?- decay.

At least 32 nuclear isomers have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, and 188Au do not have isomers. Gold’s most stable isomer is 198m2Au with a half-life of 2.27 days. Gold’s least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: ?+ decay, isomeric transition, and alpha decay. No other isomer or isotope of gold has three decay paths.

Symbolism

Gold has been associated with the extremities of utmost evil and great sanctity throughout history. In the Book of Exodus, the Golden Calf is a symbol of idolatry and rebellion against God. In Communist propaganda, the golden pocket watch and its fastening golden chain were the characteristic accessories of the class enemy, the bourgeois and the industrial tycoons. Credit card companies associate their product with wealth by naming and coloring their top-of-the-range cards “gold;” although, in an attempt to out-do each other, platinum has now overtaken gold.

On the other hand in the Book of Genesis, Abraham was said to be rich in gold and silver, and Moses was instructed to cover the Mercy Seat of the Ark of the Covenant with pure gold. Eminent orators such as John Chrysostom were said to have a “mouth of gold with a silver tongue.” Gold is associated with notable anniversaries, particularly in a 50-year cycle, such as a golden wedding anniversary, golden jubilee, etc.

Great human achievements are frequently rewarded with gold, in the form of medals and decorations. Winners of races and prizes are usually awarded the gold medal (such as the Olympic Games and the Nobel Prize), while many award statues are depicted in gold (such as the Academy Awards, the Golden Globe Awards the Emmy Awards, the Palme d’Or, and the British Academy Film Awards).

Medieval kings were inaugurated under the signs of sacred oil and a golden crown, the latter symbolizing the eternal shining light of heaven and thus a Christian king’s divinely inspired authority. Wedding rings are traditionally made of gold; since it is long-lasting and unaffected by the passage of time, it is considered a suitable material for everyday wear as well as a metaphor for the relationship. In Orthodox Christianity, the wedded couple is adorned with a golden crown during the ceremony, an amalgamation of symbolic rites.

The symbolic value of gold varies greatly around the world, even within geographic regions. For example, gold is quite common in Turkey but considered a most valuable gift in Sicily.

Toxicity

Pure gold is non-toxic and non-irritating when ingested and is sometimes used as a food decoration in the form of gold leaf. It is also a component of the alcoholic drinks Goldschläger, Gold Strike, and Goldwasser. Gold is approved as a food additive in the EU (E175 in the Codex Alimentarius).

Soluble compounds (gold salts) such as potassium gold cyanide, used in gold electroplating, are toxic to the liver and kidneys. There are rare cases of lethal gold poisoning from potassium gold cyanide. Gold toxicity can be ameliorated with chelating agents such as British anti-Lewisite.

While hot rocks can be extremely annoying (article on: “What are hot rocks?”, they are really a good indicator that gold may be nearby. As most experienced prospectors know, gold likes to hang around in highly mineralized ground. In actual fact, the more severe the soil is and the more hot rocks there are, the better the percentages of strolling over a gold nugget. Learning what hot rocks are and how to detect around them does take endurance and patience, however with a little practice you’ll be able to work around them in no time. Listed here are a number of suggestions that I have found useful for dealing with them:

1) If your detector has an adjustable Gain, strive lowering it and elevating the coil slightly above the ground. This may cause a loss of some depth and sensitivity, however may be extra preferable than listening to the constant zips and boings of the hot rocks.

2) If you’re operating a VLF (Very Low Frequency) detectors, your greatest bet can be to use a DD coil. The DD configuration will considerably assist scale back the effects of hot rocks and floor noise.

3) In the event you occur to be using one of the newer Pulse models, you’ve got a lot more options. With the new soil timings discovered on these machines it’s doable to re-work hot rock infested areas using the Monoloop coils. We have found a lot gold on pre-worked patches through the use of the setting (some standard, some automatic – depending on make/model of your detector). These timings are incredibly highly effective tools, and are making it potential to recover gold that has been hidden for decades beneath a veil of noise. If you happen to own any one of the pulse machines, I might highly encourage you to go back to site that’s plagued with hot rocks. Should you one of the first detectorists with this newer technology to hunt it again, you possibly can do exceptionally well. There is an old hydrolic operation that I keep going back to and doing pretty well. It has been hit by many detectors over the past decade that I am sure have pulled many ounces of nuggets from the area. With my pulse detector that completely ignores hot rocks, I am able to go into the bowls where the concentrates are thick with hot rocks and pick out small nuggets that the other detectors have passed over. This method continues to pay!

Many time hot rocks may be tuned out by ground balancing directly over them. This will likely eliminate the hot rock, however in turn cause the bottom to change into noisy. Due to this fact I do not advocate this practice. I discover it is more efficient to simply study the soil and take care of the hot rocks as they come. This usually entails kicking them apart with my boot or simply tossing them off into the bushes. The simplest strategy to deal with hot rocks is to easily memorize what they look like in a particular location. This way it is possible for you to to quickly acknowledge them whenever you hit them. Fortunately the new rocks in any given area are usually pretty homogenous, so it’s best to only should memorize a few completely different types.

One thing worth mentioning is that hot rocks can mask a nugget. We have discovered many little nuggets here in Oregon hiding directly under them. So, in case you hit one and for some reason it doesn’t sound the same as the remainder, it is best to transfer it out of the best way and test the ground beneath. A common rule is, if the hot rock shouldn’t be too big, kick it out of the way. Or, “When it doubt; kick it out!” I do not enjoy listening to hot rocks anymore than you do, but as I discussed above, I do like seeing them. If you end up in an unusually noisy patch of hot rocks, slow down and work the world very carefully. These spots do require further effort, however you by no means know, that next signal you get may very well be the start of a brand new patch!

Practically all soils associated with gold prospecting areas include “hot rocks”. A hot rock is a rock which doesn’t include gold, but which causes the metallic detector to sound off. They come in two primary types.

Negative scorching rocks (also known as “cold rocks”) are normally magnetite or contain magnetite. They provide a negative response because their ground balance value is the next quantity than the soil they’re found in. They are usually dark in color, and are often heavy because of their iron content. In some instances they’ll have rust stains. They are normally interested in a magnet, and

for that reason gold prospectors always carry a magnet-the final word ferrous/nonferrous discriminator. In motion all metals mode, negative hot rocks produce a boing sound moderately than the zip sound of a metallic target reminiscent of gold. Another difference is that as you sweep forwards and backwards over a sound to test it, a “zip” sound will appear to remain in the same place whereas a boing sound will seem to be in two totally different places and to wander around. Be taught these variations and it is possible for you to to disregard negative hot rocks.

Positive hot rocks are usually iron-bearing rocks which have been oxidized by natural weathering processes, such that their ground balance number is a number lower than the soil they’re discovered in. They’re usually small, right on the surface, and sound just like a gold nugget. They’re frequent in many gold prospecting areas. They are usually, however not always, drawn to a

magnet. They’re most often reddish in colour but are sometimes black, brown and even yellow.

A particular class of optimistic hot rock is electrically conductive rocks. In gold prospecting situations the most typical electrically conductive sizzling rocks are sulfide ore (peacock ore, pyrrhotite, etc.) crystals. These can sound identical to a gold nugget, however in lots of geological settings the gold shouldn’t be present in the same sort of rock because the sulfide ores. Subsequently the sulfide ore signals will be ignored as soon as the host rock will be identified. A couple of geological settings include graphite or graphitic slate rock which tends to offer a very broad signal which doesn’t sound like gold and which can’t be ground balanced out. If the rock sounds like metal, is black in color, and you’ll write on paper with the rock as you would with a pencil, you’ve obtained graphitic rock. As a way to use a metal detector where there’s graphitic rock you’ll probably have to scale back the sensitivity setting of the metal detector.