[meteorite-list] Analysis of meteorites with an SEM

From: ensoramanda <ensoramanda_at_meteoritecentral.com>
Date: Sun, 24 Feb 2008 02:12:44 +0000
Message-ID: <47C0D29C.5020302_at_ntlworld.com>

Hi all,

Over the years I have always enjoyed all the images people have posted
showing meteorites in many ways, beautiful photographs, thin sections
etc etc. I wish to share some images and data of another kind showing
meteorites in another light.

Yesterday I helped my local University with their open day by setting up
a display of some of my meteorite collection and talking to students and
on local radio. In the afternoon I was let loose in their labs where we
cut a couple of meteorites, a NWA 4576 mesosiderite and an unclassified
piece (ordinary chondrite). A great feeling being the first to see the
inside of a meteorite since it was formed.

Then I was shown how to use their SEM (scanning electron microscope) and
left to collect data from my samples....a fantastic priviledge to be
allowed to scan around my own pieces like that. I ended up with nearly
40 images and related graphs showing the elemental compositions of
various parts.

For those not familiar with an SEM, the samples are loaded into a vaccum
chamber and you then drive the samples around on the computer screen
looking for unusual areas to point the cursor at. Once the areas or
points are chosen the SEM can then almost instantly give you a graph
showing the elements and their percentages...from which a trained eye
can work out the minerals present.

Not being trained in any way to do this then this where I lack the
knowledge to interperate the data...although I can take a good guess at
which is likely to show olivine, troilite. The lighter areas of the
images are the nickel iron.

If anyone on the list has had experince interpereting this sort of data
I would be interested in your comments on what some of the data shows.
For others on the list it might just be an opportunity to look at some
images of meteorites in another way.
So feel free to download the word document (nearly 7 meg) and have a
look if you wish.

http://www.gigasize.com/get.php?d=pz9y3b013tb

(I hope this link works)

The first 7 pages are sample 1, the chondrite, and the rest are NWA
4576...which seems to be the most interesting.
The 2 pages of percentages show 2 areas of Nickel Iron which I guess may
be Taenite and Kamacite due to the different nickel to iron ratios.

I am intrigued by the areas showing carbon dots and the areas with
chlorine and iron and oxygen which I presume are due to weathering?

I will take some photographs of the samples as cut if anyone would like
to see the slices and end cuts.

Graham Ensor, Nr Barwell, UK
Received on Sat 23 Feb 2008 09:12:44 PM PST