Nickel drop test for meteorites

[Briansl]

Hello

I have a question regarding the nickel allergy drop test with cotton swabs you can buy online for use on stonier type meteorites.

Is that test better for a solid iron nickel meteorites or does it work on all meteorites, ordinary, enstatite, on the fusion crust, or are some rocks just too low in nickel for a drop test to detect?

Thank you.

 

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[Red-Coat]

Welcome to Tnet.

I have a mild allergy to nickel and so have used such testing kits (I tried one called “Nickel-Alert” and another called “Reveal & Conceal”). They’re “qualitative” rather than “quantitative” but very sensitive, and will give a positive result for metallic nickel contents above about 10-15ppm. For that reason, they were of limited value to me since my allergy is only mild and I don’t generally get a skin reaction at those low levels. There are more expensive test strips available (eg Quantofix) which give a better idea of how much nickel is present but at best they’re “semi-quantitative”.

There’s also a product available with the registered trade mark “Meteorite-ID” but it’s essentially the same test solution, branded to attract that market. It doesn’t “identify” meteorites, but gives a positive result in the same way as the allergy-test kits when there is more than about 10-15ppm of metallic nickel.

These tests have their place, but are of limited value. Nickel-containing minerals (non-metallic) are not at all rare in terrestrial rocks, but most of them won’t give a positive result to a test kit. However, neither will the classes of meteorite which have (virtually) no native metal. Terrestrial rocks containing metallic nickel (alloyed or not) which will give a positive result are rather more rare. However, industrial man-made materials such as metallic slags may well also give a positive result.

That means if you have a specimen in which you can see native metal (including as shiny flecks or veins) and it tests negative for nickel, then it’s not a meteorite. But the reverse is not true. If you can see native metal and it tests positive for nickel, you can’t say it is a meteorite… only that the possibility is elevated to the extent that further testing may be worthwhile if other characteristic features of meteorites are present.

 

[wedoitall]

"One easy test for grains or slabs that are at least a few millimeters in size is simply to measure the electrical resistance with an ohmmeter. You can buy handheld multimeters in any good hardware store for $30. In resistance mode (ohms), putting the leads some distance apart on any of these iron meteorites would give a low resistance – <100 or probably <10 ohms. This test may not work on an ordinary chondrite because the iron grains are not connected. Shiny hematite or pyrite aggregates will have high electrical resistance because they do not conduct electricity."

Metal, iron, & nickel | Some Meteorite Information | Washington University in St. Louis

sites.wustl.edu