This article is about finding gold with a metal detector in the hydraulic mines of the Sierra Nevada mountains, California. The methods described are for the Fisher gold bug (GB) and Gold Bug 2 (GB 2) and the Whites Gold Master II (GM II) and Gold Master V/SAT (GM V/SAT).
This information may or may not be applicable to other detectors and other areas such as stream beds or the desert areas of the south west. 
Hydraulic mining was carried out during the gold rush but was pretty much stopped by a court decision in 1884 because of the millions of cubic yards of debris washed into the rivers.
This method used high pressure jets of water from cannon like nozzles called monitors or giants to cut into the gold bearing gravels and wash it into large sluice boxes.
The most productive areas for this method were ancient stream beds that were covered by volcanic debris forty million years ago (give or take a couple years).
Today, these mines are open areas with a few stunted trees, many stacks of rocks and in most of these mines, a lot of exposed bedrock.
The size of these mines range from a couple acres to well over a square mile. Most of the hydraulic mines in California are north of Highway 50 although there are a few to the south.
Once you have seen a two or three of these mines, you will easily be able to recognize others even from a couple miles away. To get an idea of the scale of these mining operations, there are three guys standing in the lower left of the photo.
What you need
Metal detector
While any metal detector is capable of finding gold, you really need a machine designed for prospecting.
Unfortunately, these detectors aren't very good for much else. Some of the features that set these detectors apart from coin or treasure machines:
- They usually use a higher operating frequency for increased sensitivity to small pieces of gold.
- Elliptical coils which have some of the advantages of a large round coil (depth) and a small coil (ability to detect small targets). They also get into tighter places.
- Multi turn ground balance controls for very precise adjustmets in highly mineralized soil. No automatic ground balance here.
Basic tools
Having spent many weekends in these mines, I have had the opportunity to see what kind of stuff other nugget shooters carry while detecting.
Some folks strap the detector box on their chest and put on a belt with two loaded tool pouches and other tools hanging from the belt loops. I come from the minimalist school. I have a belt with a tool pouch and one loop.
The pouch has a small pocket that holds a plastic gold bottle, a larger pocket to hold trash and the largest pocket holds a Jimmy Sierra tray (more on this later). I carry the detector and a small pick with a 15 inch handle.
The belt loop is usually empty unless I think I might need something special like shears for lopping off low growing manzanita branches.
Recommendations:
* Fisher gold bug 2 detector. A Whites GoldMaster II or V/SAT is an excellent (and less $) second choice. Don't forget a coil cover. They are much cheaper to replace than coils when they wear out.
* Fisher ear phones are the best I have found for either Whites or Fisher detectors. They are quite sensitive and they have a built in diode that quiets the very loud signals.
* The pick I use has a 15 inch wooden handle with a magnet at the end. The head is made from an automobile leaf spring. It is about two inches wide at one end and tapers to a point at the other. This pick has the weight to hack into bedrock and the strength to pry small boulders from their homes. I have seen a pick advertised in the mining magazines which looks similar called the Mag-Na-Pick.
* The Jimmy Sierra tray is a black plastic tray about six by eight inches. If you can find a similar size tray, just cut the lip off one end and it will be close enough.
* An unbreakable container to hold your gold. A 35 MM film container will work.
* A small but detectable piece of gold stuck on a plastic bottle cap or something similar to be used as a test piece. I just used tape to stick mine on. If you don't have any gold yet, use a flat piece of lead maybe about twice the size of a pin head.
A few other items can be handy up in the digs:
A small coil for your detector can dramatically increase your gold finds. You do lose some depth (not much though) but you gain by getting between and by getting closer to rocks and other obstructions that others have passed by.
This can be virgin ground even in the hardest hit areas. Someone I know is using the six inch elliptical coil on his Gold Bug 2 almost exclusively and he is doing very well. I am starting to move in that direction too.
My problem is, if I head for the hills with two coils, I'm always worrying about having the wrong coil on the detector no matter which one I am using.
For cutting branches, small or large lopping shears or even a pruning saw will do the job.
A small rake or a three prong hand cultivator works well for breaking up soil.
They work even better if you weld a piece of flat bar stock on top of the teeth so you can turn it over and use it as a scraper. These rakes work especially well under bushes (right in photo).
If you get into a nail patch, a magnet rake helps to clean it out. These patches can be productive because no one has really detected them.
The rake is made from two pieces of 3/4 inch aluminum conduit and the teeth are cow magnets . This idea came from Larry Salle's excellent book "Zip Zip" (left in photo).
Another way to clean up nail patches is to get one of those magnets you see advertised that is supposed to lift 500 pounds or something similar. Just attach the magnet to a stick and it's ready to go (center in photo).
One other item to think about are the shoes you wear while nugget shooting. Gold detectors are very sensitive and will "see" any metal in your shoes from a surprising distance. In addition to the obvious metal eyelets etc, many hiking boots and shoes have metal shanks in the soles.
Usually, there is information on the shoe box or a tag attached to the boots describing the features. Try to find a pair that doesn't have any metal in or on them.
Finding Gold
Throughout the rest of this article, I am going to suggest experiments and other things to try. These suggestions should help to make using your detector more comfortable and hopefully, flatten the learning curve a little.
They are best done in the area where you will be searching but you can do most of them at home if you can find a "clean" place.
Warning - Beginning of soapbox - In the preceding section I left out the most important thing you need. That is the patience and perseverance to learn a new skill and to never think you've learned it all.
You may have purchased your detector from a dealer who implied all you have to do is wander around the gold country waving your new detector and you will get rich. It doesn't work like that!
I didn't find anything but trash for the first two weekends but on the third, I found one - and then another - and then another ..... and it got easier after that. These machines are very sensitive and are constantly talking to you. You have to concentrate and try to figure out what they are saying.
My advice for beginners:
* Make sure you are in a place where there is detectable size gold.
* The ground should have low mineralization and it shouldn't vary much.
* If you are in such a place and you aren't finding any gold, Figure out what you are doing wrong instead of looking for a new place.
* If there is someone around that is finding gold, most will be willing to take a few minutes to help you get started.
* Dig everything at first but try to guess what it is.
* Leave the spouse, kids and dog home while learning. I have seen a lot of frustrated folks who have to stop and look for the dog or the kids start saying "when do we go home?" - "I'm tired" - "I'm hungry" etc.
* Never stop experimenting and learning.
- End of soapbox
Adjusting your detector
This includes the physical set up and tuning of the detector. The intent is to focus on stuff that either isn't in the manual or isn't emphasized.
Setting up
The first thing to think about is setting up the detector for your body dimensions and style of searching. When you are swinging the detector all day, these adjustments are critical.
Usually, the coil should rest on the ground a few inches in front of your feet when you are standing straight up. If the stem is too long, the detector will be unbalanced and your arm will eventually let you know.
If is too short, you will be slightly bent over and your back will complain. When you think it's about right, try one notch either way for a couple hours and see how you feel.
When you know it is right, mark the hole so if you collapse the detector for storage etc, you can set it back quickly. Oh, don't forget to tighten the collar.
The Gold Masters have an alternate mounting location for the control box under the arm rest. I recommend you at least try this location for a day or two to see if you like it.
It makes the detector perfectly balanced but I found it a little more awkward to twiddle with the controls and it got in the way when I was separating a piece of gold from the dirt. It may work great for you though.
The gold bugs are light enough so you don't have to worry over such things unless you are using a 14 inch coil. I have a big coil and found that after a couple hours of swinging it, I thought my arm would fall off!
After I got home, I decided to try belt mounting the control box and adding a weight equal to the box (about a pound) under the arm rest. It feels a lot better now. If you decide to belt mount the Gold Bug box, here is a trick that works great.
Call up the nice folks at Fisher and order the little bracket on the stem that the box slides on to. You can then attach the bracket to a belt using flathead screws and T-nuts. Countersink the bracket for the screw heads and put the nuts on the inside of the belt Be sure the screws don't protrude from the nuts.
With this arrangement, you can slide the box on and off the belt in a couple seconds instead of threading the belt through the slots.
The coil should be adjusted so it doesn't flop around but it does need to be able to move fairly easily. It is very important to keep the coil parallel to the ground so you will be moving it often as the slope changes.
Notice the screw that attaches the coil to the stem is plastic. The implication of this is that the less metal near the coil the better. Since the cable has metal in it, one or two wraps around the lower stem is the maximum.
You can wrap the rest of the cable around the upper stem near the control box but if you use two coils, it is quicker to wrap the cable horizontally between the stem and the bottom of the box when changing coils.
It is important that you never put any strain on the cable (wires will break) but you don't want the cable moving too much in relation to the coil (false signals) either. I set the coil a little past perpendicular to the stem and wrap the cable over the top of the stem (the cable comes out on the left side of the coil so it should wrap from left to right over the top of the stem).
If you find you are getting a lot of false signals because the cable is floppy or you don't have enough range of movement, you should make adjustments right away.
Tuning
The proper tuning of your detector (and keeping it tuned) will be a big factor in how much gold you find or even whether you find any gold at all.It is a fairly quick and easy procedure that will become second nature to as you gain experience.
Tuning is simply setting the the electronics in your detector to the local conditions (such as ground mineralization, temperature etc) and your equipment (such as headphones and the coil you are using).
The three controls that aren't fully covered in the manual are the , threshold and ground balance.
Sensitivity
I always try to run the sensitivity wide open (and with the GB2, audio boost on) but there are many high mineralization areas where it will drive you nuts and you won't be able to distinguish between a real target and all the other noise.
Trust me, in these locations, you will find more gold even when you desensitise your detector. The mode and mineralization switches on the GB2 and the VSAT switch on the GM may help in these conditions (see the manual).
As you gain experience and learn what the different sounds mean, you may be able to increase the sensitivity in the hot areas and hopefully find more gold. When in doubt, drop your test piece on the ground and make sure you can hear it.
Threshold (Gold Bug) or Tuner (Gold Master)
Although this control changes the loudness of the threshold tone you hear, it is *NOT* a volume control. Simply stated, the lower you set the tone (and still hear it OK) , the more sensitive your detector will be.
This implies you should set the volume control on the gold bug to max before setting the threshold because you can then lower the threshold and still hear the tone at a comfortable level. If you use headphones with built in volume control/s, you need to adjust them so you can hear the tone OK but won't blow your ears off when you wave the coil over a railroad spike.
There is one annoying problem with all the gold detectors I have used. The tone drifts when the temperature changes. You have to keep readjusting the threshold in the morning as the temperature goes up and again in the evening as the temperature goes down. Sometimes you even have to fiddle with it when moving from sunshine to shade or vice-versa.
Ground Reject (Gold Bug) or G.E.B (Gold Master)
This one seems to confuse many beginners and it is the one you need to readjust the most. So, what does it actually do you ask? It tunes the detector to the mineralization in the ground so that moving the coil in relation to the ground doesn't give you false signals.
If the ground balance is not just right, then moving the coil over a small hole or lifting it to go over a rock will give you a signal. If it's REALLY not right, then moving the coil at all will give you all kinds of confusing signals and you won't be able to hunt at all.
Here's a scenario that has happened to me too many times: I'm wandering around not paying close attention to the changing mineralization and I think I hear a little signal. I dig a little hole and check the dirt - nothing. I recheck the hole and the signal is louder now.
I repeat the digging and checking and the signal is even louder now. On the third dig I usually enlarge the sides of the hole in case I wasn't centered over the target. The signal is louder but not as "zippy" as it was.
Now I begin to suspect the adjustment of the detector, move off to the side of the hole, re-ground balance and recheck - no signal - time wasted.
The manuals explain the procedure pretty well but there are a couple things I want to add.
* You only need the pump the coil six inches or so and even less as you get better at it. I have seen a couple beginners moving the coil up and down from the ground to above their heads.
* You can get a little confused about which way to move the ground balance control depending the sound your detector makes as the coil movins up or down. Remember it this way: If the tone gets louder when the coil moves down, turn the control down like a radio. If it gets softer going down, turn it up.
* As the ground mineralization changes, you will have to change the ground balance as you would expect. You will find that as the ground gets hotter the adjustment becomes more critical. In ground that is not so bad, you can just use the corse control but in hot ground, you will need to use the fine control.
* Your detector will be a little more sensitive to gold if your ground balance is *SLIGHTLY* positive (louder going down). It should never be negative. Experiment: If your detector is a little more sensitive with a slightly positive ground balance, what happens if you are in a patch with a lot of very small gold pieces and you turn the ground balance more positive?
Other Controls
* To discriminate or not to discriminate - that is the question. The gold bug 2 and the Gold Masters have iron discriminate but they are very different in the way they operate.
Both require the coil to be pretty much dead centered over the target and the signal must be of a certain strength for the discriminate circuitry to do their thing.
In the iron discriminate mode, the Gold Masters still have the threshold tone and signal every target but they insert something like a hiccup in the middle of the signal if it is "sure" the target is ferrous.
The advantages to this design are that you can leave the detector in the discriminate mode all the time because you don't lose any sensitivity or depth (some will argue that point) and you can be pretty confident the target is ferrous if you get an iron signal although a couple guys told me they found the Gold Master sometimes lies (iron signal but target is gold) in some fairly specific areas in the desert.
The main disadvantage is the "sure" part. You will get "good" signals from almost all hot rocks (more on them later) and small or deep targets. I have dug eight inch deep holes and only then the GM starts signalling iron (the nail being a couple inches deeper).
The false signals on hot rocks bothers me the most though. The Gold Masters have a meter that is supposed to help with the iron discriminate but I have found that if it moves at all, it goes full scale and you get the audio iron signal anyway so the meter seems pretty useless except as a battery check.
The Gold Bug 2 goes silent ( no threshold tone) in the iron discriminate mode and all the other adjustments seem to go to some factory preset values.
The advantage of this iron discriminate design is it knocks out virtually all hot rocks but there are some disadvantages. The main disadvantages are reduced sensitivity and depth so you usually wouldn't hunt in this mode, a steeper learning curve, plus more false iron signals than the Gold Masters. 
In theory, it is supposed to only beep if the target is non-ferrous. In practice though, many iron targets get through. The shape of the target seems to have something to do with it.
For instance, if the coil moves across a nail, you get a signal but when the coil moves at 90 degrees (along the length of the nail) you get no signal. Also, flat pieces of tin cans get through.
Here are a couple examples of the steeper learning curve: Say you are hunting in the normal all metal mode and you hear a semi weak signal.
You flip the switch to the iron discriminate mode and the signal is gone. Is it because the target is ferrous or because of the reduced sensitivity and depth in this mode, the target just can't be detected? You can learn how strong a good signal has to be in the normal mode to be detectable in the iron discriminate mode but it takes a while.
The opposite is also true. If you hear a strong signal and it is still strong in the iron discriminate mode, is it because it's a good target or iron trash that because of it's size and/or shape gets through the discriminator? If the target is a nail laying flat, going over it at different angles will usually tell you.
If that doesn't work, I usually raise the coil up off the ground until the signal gets weaker in the normal mode and see if it is still there in the iron reject mode.
While you can learn how weak the signal has to be to get an idea of what the target is, it may be best to dig these targets anyway since this isn't as reliable as the other two methods.
Let's look at the good side of this discrimination scheme.
Although you lose some depth and sensitivity and usually can't hunt in this mode, the ability of knocking out hot rocks really saves time. If I am in an area with zillions of them, I can turn on the iron reject and only dig the signals I hear.
Also, I have found many small (usually pea size or smaller), rounded, reddish-brown rocks that look and sound just like most of the small hot rocks in the area. If you were using a Gold Master or the original Gold Bug, you would probably put them in your trash pocket and move on.
If they get past the Gold Bug 2's iron reject, almost all of them have at least one piece of gold inside - most have more than one. I call them "3 packs" or "5 packs". I would much rather dig nails than hot rocks because they can be separated faster especially with a magnet and nail patches have never been properly hunted!
VSAT control on the Gold Master - I never found any use for it but I don't hunt in the desert where it is intended to be used.
Mode control on the original Gold Bug - Set to Autotune, the other two positions are useless.
Searching
OK, you are in a hydraulic mine, have all your stuff together and your detector is all tuned up, lets go find some gold.
I think the best way to start this section is to take a quick tour around a typical dig. Most of the area you will want to hunt will be reasonably flat with exposed bed rock here and there.
Quite often, there will be steep banks of reddish gravel around the flat area on at least one side. These banks can be two or three hundred feet high. This is the ore that was being mined. Take a close look at the gravel in the banks so you will recognize it later.
If you run your detector over the stuff, you will probably find many hot rocks. Usually the bottom two or three feet had the best gold and the old timers sometimes just washed the rest into the drainage because there wasn't enough gold to pay for the wear and tear on their sluice boxes.
There had to be some place for the water and tailings to drain out of the digs. The mine could be open on one side or there may be one or more tunnels. If there is a tunnel, the miners often put their sluice in it.
Lets take a closer look at the "reasonably flat area". In the typical mine you will usually see some stunted trees eking out an existence by sinking their roots into bed rock cracks and some trees that enjoy a better life in areas where the gravel or dirt covers the bed rock.
There are often many piles of rocks that were either too large to move or would cause too much damage if allowed to go through the sluice box.
In general, the best places to look are on bed rock or where dirt or other material appears to be shallow enough that any gold on bed rock is in range of your detector.
