Gold Detection and Black Sand

There are several methods to search for the native gold (in dust or nuggets) alongside the rivers.


1. You can randomly stumble upon a deposit by moving tons of sand with your shovel and pickaxe, or slowly pass it through a gold pan or a more sophisticated sluice box. After a day of intense work, you might be lucky to retrieve a few grams of this precious metal.


2. You can also prospect for big gold nuggets with a good metal detector. However, it might take a long time and, most importantly, it is necessary for the gold to exist in the river in the first place, which is not always the case. It might take weeks before you find something.


3. Another, more efficient and effective method is not to look for gold itself, but for the magnetic Black Sand.


That latter method allows for a higher payoff and is less strenuous. We recommend using the magnetometers, especially the popular MAG 505, the most affordable and efficient magnetometer of all. In fact, it is much easier to detect the concentrations of Black Sand for its strong magnetic field than gold itself.


The concentrations of Black Sand are most commonly found on the paths of the rivers or the streams that transport the minerals off the ancient volcanic mountains. If the river is naturally gold bearing, one can find large concentrations of gold mixed with the Black Sand. One of the records of a large concentration of natural gold over 100 kg found within the Black Sand was made in French Guiana. For that reason, this above-mentioned method is the most practical of all in searches for gold in rivers.


The MAG 505

Metal detecting is the easiest way to prospect for gold in areas that are new to you.


The technology in the last decade has mushroomed making detectors cheap, precise, and lightweight. In addition, the energy requirements have dropped drastically. Most detectors now have automatic ground balancing so you can virtually turn it on and go. The latest and most effective technology is the hypersensitive two-flux gate magnetometer the MAG 505 from Deepers Detector Company:


http://deepers.com/English/Mag505.eng.html
http://deepers-detector.com/English/MAG_Description.html

Note: If you are working with a VLF detector, do not use discrimination option. Your target is not gold (unless you search only for large nuggets near the surface) your target should be the Black Sand. The best detector for this work is a magnetometer MAG 505 from Deepers Detector Company.

To use MAG 505 in searches for gold, you must first look for a likely area for gold to accumulate. Look for things located downstream of the apex of the inside bend of the wash. When water flows around the curve, it is restricted and tends to speed up until it reaches the point of the curve where it can begin to expand again and tends to slow down, dropping Black Sand and hopefully gold long the way.


To increase your odds a bit, now that you have found the perfect curve to check, find and remove a boulder and/or detect around the area of its origin. Pay special attention to the area downstream of the boulder. Treat any obstruction to the smooth flow of water around the inside bend as a potential gold trap. A boulder, gravel bar, elevation change, or even a gap along the flow will create a vortex on the downstream side of the irregularity. The vortex, no matter its size, will trap gold if gold was present during the times of water flow.


What we want is the Black Sand, which is a certain indicator that heavy stuff lies here. Using MAG 505 will allow you to detect small changes in ground conductivity and locate the large deposits of Black Sand. Discrimination will remove the response to Black Sand and reduce the sensitivity to gold as well, so do not use it. Dig up the area that the detector indicates all the way down to bedrock and pan or dry wash it as usual. With a little luck, you will find the gold.

TAKE INTO CONSIDERATION


GOLD IS HEAVY AND IS ALWAYS FOUND ON THE BEDROCK

Gold is extremely heavy, six or seven times heavier than rock, and, therefore, it settles on the bottom of the gold bearing streams. The key word here is “bottom”. Gold's excessive weight forces it down-downhill, downstream, down into the sands and gravel, down into bedrock cracks and crevices, and down in your sluice box or gold pan. Gold is assisted in its downward movement by wind, rain, earth tremor, rockslide and agitation. Once gold settles on the creek bed, it will sift downward through the lighter sand and gravel. Because of its weight, it will continue to sink until it reaches bedrock, where it will become trapped in crevices and such.


WATER VELOCITY

Because gold has a tendency to sink, it will concentrate wherever the creek slows down or loses sufficient velocity to drag it further. In other words, if gold is dragged down a mountainside to a deep, motionless pool, it will immediately sink to the bottom. The first principle of prospecting, then, is to search where the flow of water decreases.


Therefore, pay special attention to the edges of whirlpools, at the tail of eddies, beneath waterfalls and in deeper pools. Fine gold is usually found in the shallow areas, and coarse gold in the deeper areas. A popular misconception is that all nuggets sink immediately to the bottom at, or near, its source. This is generally true, but depends a great deal upon the size of the nugget and the flow of the water. For example, a stream flowing at only one-half mile per hour can lift and carry gravel about the size of a pea. At five miles per hour, stones the size of cannon balls will tumble freely. When the velocity is slightly greater than 20 miles per hour, boulders that weigh nearly a ton can be moved gradually. In addition, during spring run-off, the velocity is often much greater than this.


OBSTRUCTIONS

Gold tends to be deposited at any point where obstructions hinder or halt its progress. Large rocks beneath the surface act as natural riffles and can accumulate rich pockets of placer gold. Likewise, a fallen tree trunk or other natural obstruction will impede the gold's progress, causing it to sink. If a tree trunk, embankment or other obstruction projects from the bank into the current, a vortex is likely to form. It is in these deep pools that many of the richest "glory holes" have been found. However, these pools are usually deep, and may be accessible only through the use of scuba gear, underwater dredges, and the like.


SHORTEST DISTANCE BETWEEN TWO POINTS

Again, due to its weight, gold tends to take the shortest route as it is carried downstream. It therefore deposits on the inside of bends and curves in its journey. Then, as these areas tend to lose velocity, the gold sinks to the bottom. Quite often the suspended sand, silt, iron and gold particles will build up until a small drift of sand is formed.


This type of deposit is easily recognizable above or below water, and has accounted for many of the famous “11 gold bars" of past history. The strike at Hills Bar, near Hope in 1858, which touched off the B.C. gold rush, yielded nearly $2 million. Unfortunately, you cannot make much money trying to pan these sandbars. Even a professional gold panner would have a hard time. You will save yourself a lot of wasted effort, sore muscles and discouragement.


BLACK SAND


Black Sand Iron pyrites and Gold



Iron pyrites and Black Sands are good indications of gold. When these are spotted it is always a smart idea to prospect. Black Sands are heavier than surrounding sand and settle much in the same manner as does gold. Therefore, if Black Sands are present, you can be assured that conditions are favorable for placer gold deposits. However, since this principle was well known to early prospectors, it is almost certain that the most obvious Black Sands have already been panned. If this proves to be the case, modern technology may be very useful. A metal detector or a magnetometer can determine the presence of gold and Black Sand deposits beneath the surface, which went undetected by earlier prospectors. Some people search for small nuggets with a metal detector, and many have been successful. However, if you intend to encounter something bigger, more valuable and worth your time, use a magnetometer such as MAG 505, which has proven its efficiency and effectiveness in searches on the land and underwater (the coil is submersible, the electronic box is not).


ANCIENT STREAMBEDS

Over the tens of thousands of years that lodes were being broken up and deposited in streams, the entire topography of the surrounding area was changing. Massive landslides and titanic upheavals frequently dammed up rivers and streams, forcing the water to find alternate routes. When this happened, the former streambeds were left high and dry, and these often contained much-concentrated gold, as can be confirmed by the following example.


During the Cariboo gold rush, two strolling Chinese miners discovered a large area of gold-bearing land just north of Quesnel. China Cut, as the discovery was named, is estimated to have produced nearly $1 million. The discovery was made along the course taken by the Fraser River during the Tertiary era, 70 to three million years ago, and high above the present level. China Cut and the Tertiary Mine, 9 miles north of Quesnel, are the only two places yet discovered where the present Fraser River cuts through the ancient Tertiary riverbed.


So, always be on the lookout for signs of an ancient or dried-up streambed, as it could produce gold beyond your wildest dreams. In fact, if a major new placer discovery were to be found today, it undoubtedly would occur in an ancient, unmined riverbed!


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