[meteorite-list] Meteorite identification

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:14 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C8698E57B9_at_US-Torrance.mail.saic.com>

Hi Bob,

> I opened my yap on DOME-L (the list for planetarium professionals)
> about the so-called Leonid Meteorites. Next thing I know, I'm
> agreeing to write an article for "The Planetarian" about how to
> identify meteorites.

> Actually, I'm writing from the assumption that any sample is _not_ a
> meteorite until proven beyond a reasonable doubt.

Very sensible. At least 999 times out of 1000 you're sure to be
right.

> Thus, I'm looking for ways to _disqualify_ specimens. So
> I'm doing a little fact-checking and asking for comments.
> If it fails magnet-on-a-string, I say that it is obviously
> not a meteorite. Can I really make this generalization?

No; the odds of a meteorite failing the magnet-on-a-string
test are very small, but unfortunately not zero.

> Are there meteorites without iron?

Without appreciable elemental iron? Yes, for example some
achondrites probably have very little elemental iron. But
without any iron at all? No. Meteorites can contain iron
compounds (minerals) that magnets are not attracted to.

> Another thing I say to look for is common terrestrial minerals
> that are never found in space. I list quartz, mica, and fossils
> (Martian microfossils notwithstanding. What other very common
> earthly minerals are not found in meteorites?

There's probably a long list of sulfides, sulfates and carbonates
that are common on earth but exceedingly rare in meteorites.

> The other disqualification I mention is a porous nature (like
> furnace slag).

Pretty safe bet.

> Any other ideas?

Crystal habit is a big discriminant -- if you see crystal faces
(e.g. quartz, garnet, mica), you're done. (The exception would
be crystalline nickel/iron in an octahedrite.)

Cheers,
Rob
Received on Mon 26 Nov 2001 09:38:59 PM PST