Gerard,
I was able to get my single post "crash course" in basic mining from Mr. Greg John. Mining novices like myself will find it educational. Mr. John can be reached at nxr123@aol.com, although give the gentleman a break with your e-mails, I'm sure he's got a lot to deal with already.
"Hi! I read your questions on the thread. My name is
Greg John and I take care of the operations down here
at Death Valley Junction (just north of the Franklin Lake
Playa.) I'll try to answer your questions briefly, since you
probably have found most of the answers on-line already.
But, just in case, this e-mail might clarify some points.
Really, the distinction between the terms assay and
recovery come from traditional mining. For example, let
us consider gold. A standard fire assay for gold takes
about 30 grams (technically approx. 29.167 grams, which
is termed an assay ton) of ground ore and mixes it with
a flux usually composed of litharge (lead oxide - lead is
the "collector" of the gold), borax, sand (silica), flour
(or some such carbon source - carbon "reduces" the
lead and precious metals from their positive valance
or oxidation states to their neutral or zero oxidation
metallic state), and other ingredients. Fundamentally,
the flux lowers the melting temperature of the ore and
the lead collects the gold out of the ore. Sometimes an
inquart or addition of silver or gold is added to aid the
lead in collecting the gold.The gold is then gotten out
of the lead by a process called cupellation. The lead
is "sucked" into the cupel, leaving a gold + silver bead.
This bead is analysed for its gold content either by
separation or by disolving and reading the solution
using an atomic absorption machine or ICP, &c.; naturally,
if an inquart was used, that amount must be numerically
subtracted.
The fundamental point, is that a standard lead
fire assay such as this is not an economical
method of extracting gold from the ore.
In traditional mining, a recovery process is a economical
method of extracting gold from the ore, such as cyanide
leaching. Typically, however, cyanide leaching does not
extract as much gold out of the ore as a fire assay. Usually,
recovery methods extract on the order of 80% of the gold
that can be extracted by assay methods. It is not impossible,
though, to get as high as 97% recovery efficiency.
So the assay essentially gives you a benchmark to measure
the efficiency of recovery.
The terms assay and recovery can become
undifferentiated when the assay method is
economical; i.e., it is a recovery method.
Industry standard for evaluating an ore body is still standard
fire assay. So one approach is to treat the ore to make is
fire assayable. Thus satisfying industry standard. Another
approach is to go straight to production. Thus showing large
scale extraction.
The Johnson Process seems to be the key to making the
Franklin Lake material fire assayable and to be a recovery
process. Testing continues.
Please feel free to e-mail if you have any more questions
or comments. I hope this has been helpful.
Greg"
One of the issues that came to mind is the possibility of innocent contamination if "gold is added to aid the lead in collecting the gold" and the addition is not calculated into the reading properly. However, with the professionalism of Ledoux, a very unlikely scenario to say the least. Given the complexity of the process, I would surmise that the hire-ups at Ledoux simply wanted a re-test to make sure everything was exact given what's at stake here.
Best regards,
sh |
