[meteorite-list] Nickel tests

From: Fries, Marc D <marc.d.fries_at_meteoritecentral.com>
Date: Wed, 23 Sep 2009 14:42:02 -0700
Message-ID: <C6DFE43A.C04C%Marc.D.Fries_at_jpl.nasa.gov>

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.
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Received on Wed 23 Sep 2009 05:42:02 PM PDT