[meteorite-list] Nickel tests

From: Darryl Pitt <darryl_at_meteoritecentral.com>
Date: Wed, 23 Sep 2009 18:45:11 -0400
Message-ID: <525FAD66-398B-4507-AEDD-7AAFDAC8922E_at_dof3.com>

Further to what Marc mentioned, I've experienced false negatives which
were remedied by having first applied a few drops of dilute HCl on the
target surface.





On Sep 23, 2009, at 5:42 PM, Fries, Marc D (3225) wrote:

> I've also had mixed results with the nickel allergy kit, but I think
> I've
> figured out how to get reasonably reliable results.
>
> I think the problem is that the companies who make these things
> probably
> have liability lawyers telling them to err on the side of false
> positives
> (which won't really cause them trouble) rather than on sensitivity
> (which
> might put them in court defending against a false negative result).
> This
> means that false positives will occur.
>
> You have to liberate nickel from the sample to detect it.
> Weathering can do
> this for you, which means that you might not detect nickel in a
> fresh sample
> face, especially for a polished iron meteorite.
>
> So here's what I've found that seems to work:
>
> - start with the unknown sample and a known meteorite - an NWA unk
> will do
> as long as you are sure it is a meteorite
> - place a drop of vinegar on both samples
> - wait five minutes, so that the acid will dissolve some nickel
> - do the nickel test on both drops of vinegar
> - wait five minutes, and don't get excited if they're both red at
> first
> - compare the results
>
> In the event of a false positive, the swab will start out red and
> then fade.
> The known meteorite should stay red. If they both stay red and look
> about
> the same after five minutes, you've got a good case for nickel in the
> unknown sample.
>
> That's my take; I'm certain there is a lot of experience out there
> on this
> topic.
>
> Cheers,
> MDF
>
>
>
> On 9/23/09 2:19 PM, "Meteorites USA" <eric at meteoritesusa.com> wrote:
>
>> Hey Mike,
>>
>> I've used the nickel allergy test as well with mixed results.
>>
>> Sometimes is works sometimes it doesn't. In fact I would say it is
>> not
>> reliable most of the time unless you have a good control specimen.
>>
>> I kept getting false positives and even negative results on known
>> meteorites. In fact I took a Canyon Diablo iron that I had sliced and
>> tested it for nickel. Hmmmm imagine my surprise when it showed NO
>> results. I figure the test kit was old or out dated but whatever. The
>> point is it didn't work on a 100% genuine meteorite, why would I
>> trust
>> it with something I'm not sure of?
>>
>> There are nickel tests that work, but I have not tested many of them.
>> Your best bet is to test your test kit. Testing against a known
>> authentic meteorite is a good method. Then test against your
>> "possible"
>> meteorite. Your results will be more reliable because now you have a
>> control specimen to compare results.
>>
>> Hope this helps...
>>
>> Regards,
>> Eric
>>
>>
>>
>>
>>
>> Mike Hankey wrote:
>>> I've done some nickel tests on some of the slag/meteor wrongs we
>>> have found.
>>>
>>> It tests positive for nickel.
>>>
>>> Does this sound normal?
>>>
>>> So I guess the only way to confirm slag (if you can't do it
>>> visually)
>>> is to cut it open and if there are holes / bubbles then it is
>>> slag. Or
>>> if the slice doesn't look like a meteorite slice it is slag.
>>>
>>> For the record, I am personally looking for west like fusion crusted
>>> stones and this is what I am training people to look for. At the
>>> same
>>> time when I get reports about weird rocks I have to follow up and
>>> take
>>> a look. Not all slag looks the same, there are a lot of different
>>> types. I'm getting pretty good at identifying / ruling things out,
>>> but
>>> the nickel test threw me for a loop.
>>> ______________________________________________
>>> http://www.meteoritecentral.com
>>> Meteorite-list mailing list
>>> Meteorite-list at meteoritecentral.com
>>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>>>
>>>
>>
>> ______________________________________________
>> http://www.meteoritecentral.com
>> Meteorite-list mailing list
>> Meteorite-list at meteoritecentral.com
>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>>
>
> ______________________________________________
> http://www.meteoritecentral.com
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Wed 23 Sep 2009 06:45:11 PM PDT