Meteorite Authentication
A nickel spot test is one of the most common ways to screen a suspected iron meteorite, and one of the easiest to get wrong. In this short clip the same meteorite reads negative twice and then positive, depending entirely on how the surface was prepared.
A nickel test on a Gebel Kamil iron meteorite, run on three differently prepared surfaces.
Two negatives and a positive, on one meteorite
The specimen is Gebel Kamil, an ungrouped iron from the Kamil crater in Egypt. It carries very high nickel, above roughly 16 percent, which is exactly what makes its behavior here worth watching. If any meteorite should pass a nickel test on sight, this one should.
First I file the exterior to expose fresh metal, place a drop of DMG reagent on it, and rub with a cotton patch. No color. The test reads negative.
Next I move to a freshly sawn face, cut before filming. Same drop of DMG, same rub. Negative a second time, on bright fresh meteoritic metal.
Then I take the other half of the cut piece, which I etched with ferric chloride. One drop of DMG on the etched face and it turns bright pink almost at once.
Why the surface decides the result
The DMG test does not react with solid metal. It reacts with nickel that is already in solution as ions. To get a reading you have to pull nickel off the surface and into that ionic form first.
Filing and sawing expose clean metal, but clean nickel-iron is fairly inert. A drop of DMG sitting on a passive surface does not dissolve enough nickel to register, so the result reads negative even though the metal is full of it. That is a false negative.
The etch changes the chemistry. Ferric chloride attacks and oxidizes the surface, freeing nickel into an available, ionic form. When the DMG meets that prepared surface the nickel is already waiting, and the color develops at once.
A negative nickel test does not mean there is no nickel. It can simply mean the nickel never made it into solution. The test reads the surface you give it.
Same meteorite. Same reagent. Three different results.
How to run the test so the result means something
For a valid reading the metal has to be dissolved or activated first, not just exposed. In practice that means a small acid step to put a trace of metal into solution before the DMG goes on, or testing a surface that has already been etched, as shown here. Skip that step and a real iron meteorite can read negative and get wrongly dismissed.
This is also why a nickel test is a screening tool and not a final verdict. A positive result supports meteoritic origin but does not prove it on its own, since stainless steel and some industrial alloys also contain nickel. Confirming a meteorite, and classifying it, still comes down to laboratory analysis and, for classified material, publication in the Meteoritical Bulletin.
Keep learning
- Meteorite vs slag: how to tell the difference
- Are meteorites magnetic?
- Authenticity and certificates
- Types of meteorites
Frequently asked questions
Can a real meteorite fail a nickel test?
Yes. If the metal surface has not been dissolved or activated, a nickel spot test can read negative even on a high-nickel iron. The test detects nickel in solution, so the surface has to be prepared before the reagent can react.
Why did the etched face turn pink when the filed face did not?
Ferric chloride had already attacked the etched surface and freed nickel into ionic form, so the DMG found nickel waiting and reacted at once. The filed and sawn faces were clean, inert metal, and a plain drop did not dissolve enough nickel to show color.
Does a positive nickel test prove a rock is a meteorite?
No. It supports meteoritic origin, but stainless steel and some industrial alloys also contain nickel. A nickel test is one screening step alongside density, magnetic response, fusion crust, and internal structure, with laboratory analysis for confirmation.
What is the correct way to run a nickel test?
Expose fresh metal, then put a trace of it into solution with a small acid step before applying the DMG, or test a surface that has already been etched. Looking for a pink to red color picked up on a clean cotton swab is the standard read.
