H&K is a well known and respected fabricator what they have written below is pretty much right. It really is worth your while to download and read the whole report.
Sluice Myths
Before we go much further we really need to look at the all to popular myths surrounding
sluice box operations and these same myths are also applicable to the operation of power
sluices and dredges. Many of these myths have been discussed at the various prospecting
forums for many years and have been presented in various professional papers but still
largely go ignored by the vast majority of people who actually use sluices on a daily
basis. For this reason we really need to revisit these myths and bring them back to the
forefront once again as they are critical elements in the process of how we use and
evaluate sluice operations.
The best and most complete list of these myths that I have run across was originally
presented in an 1989 report entitled Gold Losses at Klondike Placer Mines prepared for
the Klondike Placer Miners Association and well reprint them here.
The first myth is all too common and weve all experienced this with our own boxes and
that is: Ive recovered a lot of extremely fine gold, therefore Im recovering all of the
gold particles which are coarser.
The truth is that almost any sluice box no matter how primitive will recover a certain
amount of fine gold even as larger particles get washed away.
The second myth is also all too familiar and that is: Im recovering a lot of small
nuggets and flakes so therefore Im recovering all of the nuggets that are larger.
Actual test samples at numerous sites have shown that this myth is almost universally
false as sluices set up for fine/small gold recovery are very poor at trapping larger
particles above 16-mesh in size.
The third myth is so tired that weve all seen or heard it mentioned about a thousand
times on the discussion boards and that is: Ive panned my tailings and found no gold so
my box is getting it all. Weve talked about this before and other researchers have
proven that tailing piles are highly segregated and in their own right very effective
concentration devices so to be accurate a person has to pan the bottom of that pile in
order to actually sample what the sluice is missing. In other words you really need to re-
sluice all of your tailings to actually see how effective your sluice is working and nobody
really does this. This is where a small backpack dredge really becomes effective as a re-
sampler.
This myth is one of my particular sweet-spots as I very often rework tailing piles left by
other prospectors as they are fast and easy to do since the materials are already cleaned
and classified just sitting there at the edge of the river. Some of our most productive days
have been in working these piles on the Bear River. At one spot we could actually see
small flakes in the tailings somebody had left behind so we just hand-panned the pile and
it was pretty productive.
The fourth myth is also one of those classics that has been proven wrong by other
researchers even though it still persists and that is: I recover all of my gold in the first
few feet or first few riffles of the sluice so Im sure that Im recovering all of the gold in
my materials.
This myth is just plain wrong in almost all respects and has been scientifically proven
wrong by several researchers but it still lingers on. Basically if this is what youre
experiencing it means that the lower half of your sluice isnt working at all and that a lot
of gold is just being washed away as its pushed back up into the laminar flow strata.
The fifth myth is perhaps the most dangerous and that is when a person falls in love with
a particular piece of equipment and wont give it up even if it doesnt work. They justify
hanging on by some weird twist of logic that goes something like: This is the most
effective gear available and even if Im loosing some gold it is less than if I used some
other gear. Also heard is: Loosing gold is inevitable but this rig collects as much as is
scientifically possible so it is state of the art equipment.
A good miner never falls in love with his equipment, as there is no such thing as a
perfect piece of gear.
The sixth myth is that using riffles of any style in a sluice box will automatically
guarantee that youll be washing away about 50% of all fine gold that is contained in the
source gravels.
Like many other myths this is just not factual in reality and has been proven wrong by
many researchers. The success or failure to capture fine gold has nothing whatsoever to
do with riffles or meshes or capture fabrics but is almost exclusively dependent on proper
classification and stratification of source gravels that are run down any type of sluice at a
proper velocity.
Taken from
http://www.hecklerfabrication.com/files/sluice-build-partIII-2.pdf
{Quote} The fourth myth is also one of those classics that has been proven wrong by other
researchers even though it still persists and that is: I recover all of my gold in the first
few feet or first few riffles of the sluice so Im sure that Im recovering all of the gold in
my materials.
{End quote}
I must disagree with Myth number 4 it all comes back to how your gear was designed.These days a lot of Bankers are designed to do just that.
Another Quote from a rather well know and respected prospector whom I have talked to about this report stated. In the last 5, 10 or even 20 years incredible advances in equipment and techniques have thoroughly kicked the old 'tried and true' right out the window. And he is so right.
