Leach Gold from ore's by using
electro-chlorine. Leaches gold from ore at comparable cost to cyanide but
it is no more toxic than a common household swimming pool More Info
Now Available !
Get the most historic book ever written about gold and
precious metals processing
De RE Metallica
||Complex Ores :Myth's and Facts of Fire Assaying the
Definition Of the Word Assay: To perform a
analysis on a given sample using standard well accepted techniques and
procedures. The data derived from these analytical procedures should have
the ability to be duplicated by the assayer and other assayers
Fact: No Refinery
in the world that writes checks for the purchase of precious metals
relies on anything but standard well accepted assay procedures.
profitable operational mine relies on anything but standard well
accepted assay procedures.
people theorize that a fire assay is a worthless exercise because it fails
to recognize a multitude of problems that arise from analyzing "complex
ores". The main problem with these assertions is that what they are
calling complex ore's are usually simple and very workable (usually
worthless) ores. It seems that when a company or individual receives one
extremely high assay (usually high in Platinum Group Metals) and many low
assays on the ore body in question, it evolves into a "complex ore". This
will more often than not be used as a justification for the low assay. The
mine principles go from being novices one minute, to well seasoned experts
based on the wide variety of complex ore propaganda available to them. From
sub micron metal clusters, amorphous colloidal silica particles, to unstable isotopes, the ideas
are definitely out there to find. But the one FACT that remains
constant is that NOT one person or company on the face of this earth has a
profitable operation that is based on any these principles.
The term "complex ore" has been so misused by ignorant misguided people
that it has retained a personality of it's own. To some people the term
has a certain allure, a chance to be part interesting exciting
opportunity. They feel that they are taking part in something historic,
because they took part in or help fund someone that "cracks" the complex
It is very interesting that some assayers and chemist are able to
isolate these exotic complexes using instrument analysis or special
leaches. When it comes to a instrument analysis such as AA, ICP, or
DCP the instrument compares the sample, to a KNOWN value of precious
metals (standards). Standards are prepared by weighing real actual gold,
silver, platinum, etc......The instrument only measures what real known
values are in he standard and compares that to what real values are in the
sample. If "complex", not yet fully discovered precious metal values are
present in the ore, YOU WOULD NEED A COMPLEX UNDISCOVERED STANDARD
IN ORDER TO ANALYZE THE SAMPLE. No chemical supplier in the world sells
complex standards for analyzing precious metals.
Well accepted definitions of a complex ore
which can be difficult to assay
A true complex ore can be thought of as a
mineralogical trash pile. Ore bodies that are high in such reagent
consuming minerals such as mixed sulfides of (iron, copper, tellurium,
selenium) are traditionally known of as complex or refractory ores. Other
elements such as nickel, chrome, lead and bismuth can lead to interference
and some difficulty in an assay. But those who have experience with these
ores or even have taken the time to read the textbooks of others who have
had similar experiences, find that most all ores can be assayed by fire
assaying. I personally have yet to see a ore whose recoverable
values could not be determined by a properly performed fire assay (23
years and about 7,500 plus fire assays).
It is very common for a real complex ore to
not respond to standard fire assaying techniques. But the thing that
people who misuse this premise leave out of the argument, is that it is
usually very obvious why the fire assay was unsuccessful. An example of
this would be a high iron sulfide ore which would be considered a true
complex ore. If the sulfide ore is fluxed with the same amount of lead and
borax glass as a normal ore the result will be a gooey fused mess. A
competent assayer will use a flux designed for the "complex" sulfide ore
to insure a proper assay. The true complex ore is one that can be
difficult to assay, but those with experience and knowledge should be able
to produce repeatable assays.
Hypothesis of why fire assay may not work
Listed below are some of the 'theories" of why fire assaying is
unable to identify precious metals in certain ores. We'll refer to these
ideas as theories, but really they are just ideas.
Precious Metals Have Volatilized in
cupellation process !
It is true and factual
that some small percentages of precious metals tend to have some loss
during the cupellation process. But this fact is often misused by some
who claim 100 % of the precious metals will gas off during cupellation
no matter how you flux or pre-treat a particular ore. If all of the
precious metals volatilized off in the cupel then, we can assume that
they were present in the lead dore' from the fusion. We then
should be able to eliminate cupellation by dissolving the lead in nitric
acid and be left with a gold insoluble. Any platinum group metals could
be precipitated or analyzed by instrument for quantities present.
Another way to determine if values are
volatilizing is to have a known inquart (preferably silver) in your
assay. If something truly is present in the lead dore' that causes
volatilization then your inquart will gas off along with any values that
hypothetically are in the ore sample.
And yes very rarely (3 times), I
personally have seen inquarted samples (up to 1 gram of Silver) end up
with no button whatsoever in the cupel. Usually this is caused by the
flux and fusion time collecting just the right amounts of interferences
into the lead dore'. The fusion pours nice and the lead dore' will
appear clean. This phenomena happens due to collected amount of possibly
copper, tin, bismuth, selenium, tellurium (each sample would be
different). Usually the cupel is discolored or darkened due to the
Some main things to try in order to
eliminate this from happening are, changing your sample size and flux.
Roasting the ground ore prior to assay to remove any harmful sulfides
which might be causing the problem. Dissolve your lead dore' in nitric
acid to see if any amounts of precious metals are present. Scorification
of the lead dore' is also a well accepted procedure to remove any
un-desirable interferences before cupellation.
- You need to inquart (seed) the sample with large amounts of
Inquarting a fire assay with small amounts (5-10mg) of "gold free"
silver inquarts is a well accepted procedure. But some people argue that
in order to collect all the metals present, the sample needs to be
inquarted with large amounts of precious metals. One scenario calls for
the 1part ore to 1part silver inquart for assaying the ore. The main
problem with this is usually .999 silver, purchased from a reputable
refinery, is used in the assay. When this silver is used, it means that .1 % is
not silver and most likely other precious metals. The .1 % of
a ton equals 29 ounces of something per ton that is not pure silver.
Lets say 10 % of the impurities are gold (usually higher for
.999 silver) that would be 2.9 ounces of gold per every ton of .999
silver. If the sample was then inquarted on a one to one basis with the
silver, a cupeled dore would be produced which would contain gold and
precious metals from the silver.
A blank sample (using exact same flux and fusion times) but leaving
the ore out, is a good way to determine approximately how much precious
metal impurities are present in the silver. The dore produced from the
blank should be tested exactly the same way as any dore' used to
evaluate a ore sample, preferably side by side for comparison.
- Precious metals did not collect in lead and remain in slag!
If the ore does contain precious metals, it is possible (in some
cases) that if fluxed improperly some of the precious metals could
remain in the fusion slag. But it would be extremely rare (almost
impossible) if all precious metals in a sample (100%) reported to the
slag and ended up being repelled by the by the lead. If something was
present in the ore to cause detectable amounts of precious metals to
report to the slag, then a properly done wet acid digest or neutron
activation would show the values present.
- Must re-melt your ground slag many times in order to break down
the complexity of the sample !
Grinding your slag repeatedly is often recommended for problem
"complex" ores in order to break down the complex bonds. Some
"promotional assayers" go as far to say that re-fusing the slag will
stabilize the unstable isotopes in the complex ore. If the ore did
contain radioactive unstable isotopes of lets say gold, then the laws of
physics state gold isotopes don't stabilize into other gold isotopes.
They become other elements based on their decay methods.
- Long fusion times and high temperatures !
Some people think that the lack of high temperatures and long fusion
times are reasons that a fire assay does not recognize values in some
ores. The argument is that high temperatures can break down the
metal-metal bonds or metal clusters. Again these are ideas and no
profitable mining company or refinery implements these to recover any
extra precious metals that they feel are complex in nature.
It is well accepted by chemists and assayers alike, that if a ore will
produce an accurate wet digest then it should be able to produce
similar results when fire assayed. This being said, if a assay was
obtained by wet chemistry instrument analysis methods of lets say 1.5
ounces of gold per ton of ore. Then similar results of 1 to 1.5 oz per ton
should be able to be reproduced by fire assay. Often one or more fire
assayers cannot duplicate the false positive that can be obtained by
improperly performed wet instrument digest.
Use extreme caution when dealing (and investing large sums of money)
with assayers who claim that any ore in question cannot or does not
respond to fire assaying. Any ore no matter how "complex" in nature can be
tested for precious metals by fire assaying. Wet digests are very accurate
if done correctly, but the results should be in comparable ranges
to the fire assay, and visa versa. The main thing is not to be duped by
some part time chemist who thinks he's re-invented the wheel. Always try
to get a second or even third opinion (from reputable labs) if you hear
the term "Complex Ore, Will Not Respond To Fire Assay."
||Have a Question?
Can't find any specific info anywhere. Just send us a e-mail and we will
be glad to try to answer your question or solve your problem.
Recover Gold Dry Using RMC's Dry
Air Concentrators. Process 2-150 Tons per hour. Self Cleaning
Adjustable Speed Concentrator. More Info