Ferromanganese & Ferrochrome

A type of meteorwrong that we have encountered ~15 times (persons have sent samples or photos) is an industrial alloy called ferromanganese that is used in making steel. Ferromanganese is characterized by:

  • High density, 7.2-7.4 g/cm3, which is perhaps the first characteristic that people notice

  • 75-85% manganese (Mn), 6-7% carbon (C), with the rest being mainly iron (Fe)

  • Black exterior (presumably MnO), but not shiny or glassy like a meteorite fusion crust

  • On the inside a silvery, metallic luster consisting of submillimeter crystal grains on broken faces, very unlike any iron meteorite

  • No rust, as on many iron meteorites

  • No attraction to a cheap magnet, although it may attract a rare-earth (neodymium) magnet

Two views of a large sample of ferromanganese. This one gave a gray streak.

I might expect this stuff to be found mainly along railroad tracks, but people have reported finding it on the street, in their yards, or out in the wilderness. Pieces I have seen range in size from a golf ball to a large grapefruit.

Google “ferromanganese meteorwrongs” for more information.

We have also been sent samples of another alloy used in steelmaking, ferrochrome. It is mostly chromium (Cr, 50-70%) and the rest is mainly iron.

Ferrochrome. This sample, at least, is more yellow on the interior than ferromanganese.
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