Neither alloy occurs naturally in Earth rocks, so a natural rock that contains kamacite or taenite is a meteorite. The metal occurs as two different alloys known as kamacite (lower nickel concentration) and taenite (higher nickel concentration). “Iron-nickel” means that the metal is mostly iron but it also contains 5-30% nickel. As a consequence, meteorites have concentrations of nickel that are much greater than that of nearly any terrestrial rock. More than 95% of all meteorites contain iron-nickel (FeNi) metal. I recommend testing for Cr and Mn because most industrial (man-made) iron contains higher concentrations of these elements than does metal in meteorites. If the metal contains more than 0.05% chromium or manganese, then it is not a meteorite. A metallurgical testing lab can provide this analysis. If you have a piece of metal that does attract a magnet and want to know if it is an iron meteorite, then obtain a chemical analysis for the elements iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), and manganese (Mn). Meteorites do not contain visible grains or chunks of nonferrous metals like aluminum, manganese, chromium, copper, brass, or gold. If you have a piece of metal or a rock that contains metal but it does not attract a magnet, then it is not a meteorite. The metal in meteorites strongly attracts a magnet. Back to Some Meteorite Realities Take-home message
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