[meteorite-list] Ni-only Detector

[MexicoDoug at aol.com]

Hello Mark,

Aside from the small amounts for which you have rightly raised a red flag, 
unless the detector destructively uses a flame ionization oven to scorch the 
earth, I don't think so.  In any case, all US coins except pennies have nickel 
content in the ranges of meteoric iron, so does white gold jewelry, so a Nickel 
only meteorite detector might be good for coinshooting the beach and park, 
too.

Thirty years ago when BFO's were being overtaken by TR detectors (two 
different types of technology), we heard all kinds of promises like detectors that 
were coming out that could "discriminate" for the first three inches against 
pull tabs, etc., but at greater distances detect everything.  Then, shortly after 
that, we heard that new technology was coming out that  that could draw a 
picture in a sort of "x-ray vision" scenario for the metal detected.

While I have not kept up with the very latest (my principal detector is 27 
years old with TR/VLF modes and works just fine), I have had the opportunity to 
use plenty of new ones.  I don't think any are as good as another 1970's 
vintage Whites Coinmaster 4 for finding gold alloy, for example.  And the promises 
I mentioned were always too good to be true.  Sure, now a detector might be 
able to guess and whisper to you "Nickel" (refering to the US coin alloyed with 
25% nickel content) or something like that and flash such an icon, but after 
all these years I am not sure if even one that is capable of detecting gold 
only is around or feasible and that certainly is a worthwhile market for 
prospectors.

The problem partly is that the ground and surface matrices are unpredictable 
to make anything reliable, and even if this is possible, then there is the 
problem of the orientation and shape of the object itself.  I would guess that 
most detectors that discriminate iron still have problems with elongated iron 
objects overloading and giving false positive signals.  Finally, even if both of 
the first challenges are met then there is the degree of oxidation of the 
target.  Weathered vs. fresh.

An added consideration is that some of the best performance of a detector I 
have seen for meteorites is when the signal is low frequency and least 
processed.  Discrimination requires processing, and since iron occurs with the nickel, 
it would need to have a perfect flat (0) response to iron, a special type of 
discrimination which ignores.  That would be a fantastic detector to use over 
grounds that are laden with iron pipes, and by the way gold and nickel 
typically are very similar in signal type.  

Taking all this into consideration, I think you can confidentally chock up 
the perfect Nickel only (when alloyed in iron 5%+, etc.) discrimination as 
another one of those hopeful miracles we like to have, and also another excuse for 
the manufacturers keeping our trigger finger on yet another $500 - $1000 USD 
to spring for a new detector that can find only WMD's, or meteorites or gold or 
whatever.

Saludos
Doug


minador escribe: 

One last thing.  I heard a rumor that one of the major companies is bringing
out a detector designed strictly for meteorites that only detects nickel.
Considering how little metallic nickel is present in meteorites, I doesn't
sound feasible to me.  But I really don't know the theory behind metal
detectors, whether it's the metal or iron mineralization that sets off the
detector.  Has anyone heard about this?  It just sounds too easy.

Thanks again all for your ideas!

Take care,

Mark

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