Meteorite testing

I do not test or classify meteorites

I do not test rocks to determine if they are meteorites. I do not classify meteorites and I do not provide “Certificates of Authenticity.” I am a retired geochemist and I no longer have a laboratory. Please do not send me samples.

If, based on the information that you provide me, I think that your rock might be a meteorite, then I can probably put you in contact with someone who does classify meteorites. I will not do that, however, unless I am >95% certain that the rock is, in fact, a meteorite on the basis of the information that you provide me. It will likely cost you several hundred dollars to have it classified because classification requires a lot or time on expensive laboratory instruments. For amateur finders it is more convenient to find a meteorite dealer who will buy it unclassified as the dealer will have contacts who can classify it. Be aware, however, that most meteorite dealers will ignore you because, like me, they are contacted every day by sincere persons with meteorwrongs.

Stony meteorites

If you are particularly certain that your rock is a meteorite and you really want to convince me or any other scientist, then I urge you to obtain a chemical analysis at a commercial rock-testing laboratory. There are many labs around the world that can provide such tests. At a minimum, I need “whole-rock” data for Na₂O, MgO, Al₂O₃, SiO₂, K₂O, CaO, TiO₂, Cr₂O₃ or Cr, MnO, and Fe₂O₃ as well as trace elements Ni and Co.

See also: Geochemical Analysis Reports

I recommend Actlabs, which has branches on several continents. Ask for analysis code Meteorite(ICP/ICPMS). I have no financial interest in Actlabs, I just know that they do a good job. First, however, send me some photos of the rock so that I have the chance to say, “If that rock were mine I would not spend the money to have it analyzed because it does not look like a meteorite.”

Actlabs requests a 5-gram sample (a US nickel weighs 5 grams). They can do the analysis on as little as 1 gram, however, if you request “no LOI” (loss on ignition, i.e., % weight loss when the sample is heated to a high temperature). LOI is sometimes useful, but never critical, for determining whether or not a rock is a meteorite.

Send me a copy of the report that Actlabs sends you (the XLS file, not PDF) and I will tell you whether the rock composition is consistent with that of a meteorite. A chemical analysis is sufficient for me to say “yes, it is” or “no, it is not” 99 times out of 100. If I conclude that the composition of your rock is not consistent with any kind of meteorite, then I will probably not be able to tell you just what kind of rock it really is. Rock-type identification requires other kinds of tests. If it is a meteorite, then a meteorite petrologist is required to classify it and obtain an official name. For example, I can say with 99+% certainty that your rock is an ordinary chondrite from the chemical composition but I cannot reliably tell you which type of ordinary chondrite it is (H, L, or LL). It will be easier for you to catch the attention of an overworked meteorite petrologist or meteorite dealer if you have the compositional data.

Please

Do not bother Actlabs (or any other lab) with questions about meteorite identification. They are chemists who are experts in rock analysis. It is not their job to interpret results. They have no one on staff who is a meteorite expert. They do not classify meteorites. They do not offer “Certificates of Authenticity.” I am the meteorite composition expert, which I do for free. Actlabs sends persons with meteorite questions to me.

Check your own data with Chemical composition of meteorites.

July, 2022: I have received results of analyses of 672 samples from Actlabs and more than 140 samples from other labs. Only 9 of the rocks have been meteorites, 6 ordinary chondrites, 2 iron meteorites, and 1 pallasite. More than half of these rocks were from northern Africa or the Middle East and a couple, I believe, were stones that someone had bought or inherited.

Handheld XRF (X-ray fluorescence) analyzers

Handheld XRF analyzers *are* useful for recognizing iron meteorites. This photo was sent to me by someone who had what he believed to be a sample of Campo del Cielo, one of the most commercially available iron meteorites. The sample was tested in a coin shop. The “official” Ni, Co, and Fe concentrations of CdC are 6.7%, 0.46%, 92.9%. The meteorite might be a Campo, but then it might not. It is definitely an iron meteorite, however, which typically contain 5-25% Ni, much greater than nearly any man-made iron-rich object. (A U.S nickel coin [5-cent piece] is 25% Ni and 75% Cu.) Handheld XRF analyzers tend to overestimate concentrations rare elements like gold (Au). The concentration reported above is 0.083% (830 ppm), yet I’m unaware of any of any iron meteorite with >0.0005% (5 ppm) Au. Similarly, concentrations of copper (Cu) in IAB irons such as Campo del Cielo are typically only 0.01-0.04%.

Several persons, before contacting me, have brought their rocks to scrap-yard dealers or jewelers to have them tested with a hand-held “XRF gun.” Most of the results that I have been sent from XRF guns, however, have not been useful to determine if the rock is a meteorite. There are at least three problems. Most of the instruments are designed or programed to do analysis of metal for metallic elements, e.g., useless elements for stony meteorites like Cu (copper), Mo (molybdenum), and W (tungsten), not the rock-forming elements. So, for example, there are typically no data for Si (silicon) or Ca (calcium), critical elements for determining if a rock is a stony meteorite. Second, data for Na and Mg are also critical to distinguish earth rocks from meteorites and those elements cannot be determined by X-ray fluorescence in air. Third, it seems that some users do not really know what they are doing. For, example, a fellow contacted me once saying “Big time reputable gold dealer tested it with his X ray gun.” The big-time-reputable gold dealer told him that his rock contained “at least 15% Bohrium,” an element that does not occur in nature and the only isotope of which has a half-life of ~85 milliseconds. Others report the presence of platinum-group elements, which cannot be detected in rocks by XRF because the concentrations are too low – part-per-billion levels in terrestrial rocks and part-per-million levels in chondrites.

Energy dispersive X-ray fluorescence

I also receive reports obtained by EDX or, more properly, EDXRF – energy dispersive XRF. Such data are commonly obtained with a scanning electron microscope (SEM). In EDXRF, a small (usually much less than a millimeter) electron beam is aimed at the sample and the emitted X-rays are collected with a detector that sorts the X-rays in order of increasing energy to yield an X-ray spectrum. For the purpose of identifying meteorites, the main problem with EDXRF is that unless the sample has been ground to a fine powder, a “spot” analysis is obtained, not a “bulk” (whole-rock) analysis. We need to know the bulk composition, not the composition of several small spots that may only represent individual mineral grains. If the beam was at least 2 mm in size or the beam was rastered, an ordinary chondrite could likely be distinguished from a terrestrial rock with EDXRF data but it would not be possible to recognize most achondrites as meteorites.

X-ray diffraction (XRD)

People also send me results obtained by X-ray diffraction. XRD identifies the major minerals in a rock, not the chemical composition. In my experience, XRD results are often ambiguous. Some minerals that occur in meteorites largely do not occur at all in terrestrial rocks. So, the identification of, e.g., kamacite and troilite would be strong evidence that a rock is a meteorite. These two minerals are common in iron meteorites. Most of the minerals that are unique to meteorites are nevertheless minor to rare in stony meteorites and may not be detected by XRD. The three most abundant minerals in stony meteorites are olivine, pyroxene, and plagioclase. These three minerals are also among the most common minerals in terrestrial igneous rocks. Some minerals that are common in terrestrial rocks are rare to absent in freshly fallen meteorites. Quartz and calcite are good examples.

Bottom line: XRD can often prove that a rock is not a meteorite but it rarely provides unambiguous evidence that a rock is a meteorite.

Iron meteorites

If you have found a piece of metal that you think might be an iron meteorite, you need to have it analyzed (at a minimum) for iron (Fe), nickel (Ni), chromium (Cr), and manganese (Mn). Unfortunately, I do not know a lab that does this cheaply. If somebody out there does, please let me know. In proper hands, a handheld XRF analyzer would be useful for iron meteorites.

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