Carl,
You are right, the nickel chemical test has lots of problems with false
positives, not to mention a short shelf life after mixing. On the subject
of XRF guns, they will tell you that nickel is present but not the
percentage. The software claims that, but it is bogus. I am an operator
for our XRF gun at the Geology Museum at the Colorado School of Mines. We
have done extensive testing of this machine and found that it has severe
limitations. Here are the results of a study done at the museum:
1. XRF can only identify elements and can predict almost nothing about
quantities.
2. Most of the time it can identify the presence or absence of elements, but
not all of the time. The software will identify elements that aren't there.
You have to read the spectra to determine if the alpha and beta lines are
indeed there. Large amounts of lead or iron, (i.e.. meteorites), will block
other readings.
3. Avoid quantities, one can't even say that there appears that there is 3x
as much A as B. The only way this works is with man made alloys and pure
samples that the machine can be calibrated to.
The only good part is that I can test for nickel with a high degree of
accuracy in about 30 seconds and tell the meteorwrong bringer that I used a
scientific test to prove, what I probably already knew, that what he has is
definitely not a meteorite. It has also allowed us to correct specimens in
the collection that are mis- identified.
Blain, you need to come over to the museum, we have much to share.
Dan Wray
----- Original Message -----
From: <cdtuc...@cox.net>
To: "Paul G. Spears" <pgspe...@cox.net>; "meteoritelist"
<meteorite-list@meteoritecentral.com>
Sent: Sunday, March 13, 2011 9:37 AM
Subject: Re: [meteorite-list] Nickel found in hematite and magnetite?
Paul,
I find tons of what you are describing.
Color tests work on almost any amount of nickel and also give false
positives based on knowing exactly what shade of red to look for. I don't
know which red is the correct red.
I have an AXE that tests bright red with a red color nickel test but in
actually only has only a trace amount of nickel and scientists believe it
needs more than just a trace. I may never understand why that is. I have
been told that " nature has no way of separating the metals " but if that
is true then why is there always a different percentage of nickel and why
can it be as high as 60-ish percent and as low as just a few percent?
That said, If it is a highly oxidized iron meteorite it would have a
relatively high percentage of nickel as opposed to just a trace
percentage.
Blain's XRF gun gives complete analysis in percentages and would tell you
if it has several percent nickel. if it does then the core of the rock may
still be shiny iron. You could cut it in half and look inside.
Blain offers this service and it is quick and inexpensive. Well worth the
cost and the only way to be certain.
Carl
--
Carl or Debbie Esparza
Meteoritemax
---- "Paul G. Spears" <pgspe...@cox.net> wrote:
In a specimen that may be a hematite, a strong presence of nickel was
found.
Is that possible? While the specimen is very attractive to magnets,
tests
positive for nickel, and looks and weighs like iron, it has many pock
marks
and some white inclusions that may be quartz. Anyone come across similar
specimens?
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