[meteorite-list] WHERE ARE THE NANODIAMONDS IN PRIMITIVE METEORITES? PREL...

From: Starsinthedirt at aol.com <Starsinthedirt_at_meteoritecentral.com>
Date: Mon, 17 May 2010 01:09:39 EDT
Message-ID: <bfc.12e458ee.39222993_at_aol.com>

Shawn, Once again, a very interesting post. I like this series you have
undertaken. In your last post the idea of "low-pressure condensation being
similar to chemical vapor deposition at moderate temperatures" got me
thinking of the unusual shape of Carbonado Diamonds.

This current post gets me thinking of the enstatite fossil meteorite NWA
2965, 2828 etc. In it there are graphite specks. Those specks fool an
electronic diamond tester.

Please keep in mind, I have not found diamonds. They are way to small for
me to detect with my optical microscopes.

An electronic diamond tester works on the principle of thermal
conductivity. Diamonds conduct heat very well! I don't know if the graphite conducts
heat as well as a diamond or if the graphite is so full of nano diamonds
it fools the tester.

I have tried the tester on other graphite inclusions in many other
meteorites and the test is negative. I know this is very unscientific but I found
it interesting and perhaps related to this interesting thread.

Tom Phillips

In a message dated 5/16/2010 1:37:29 P.M. Mountain Daylight Time,
photophlow at yahoo.com writes:
Hello Listers,

Here is the second installment on the topic of nanodiamonds.

WHERE ARE THE NANODIAMONDS IN PRIMITIVE METEORITES? PRELIMINARY TEM RESULTS

BY:
L.A.J. Garvie, Center for Meteorite Studies, Arizona State University,
Tempe, Arizona 85287-1404, USA,
lgarvie at asu.edu


Introduction:

Nanodiamonds are abundant in
primitive meteorites. The work of [1] shows that most
primitive meteorites have similar matrix normalized
nanodiamond concentrations (within a factor of ca.
2.2), consistent with their location in the matrix. Huge
numbers of meteoritic nanodiamonds occur in
primitive meteorites, on the order of 3 x 1017 per gram
of matrix. Nanodiamonds from primitive meteorites
display a uniform size distribution and a mean
diameter near 2 to 3 nm [2, 3]. They occur in the
primitive members of all classes of chondrites [1, 4-7],
with matrix-normalized values from ca. 700 to 1500
ppm [1, 6]. Despite their abundance in primitive
meteorites, they may be scarce in fragile, C-rich IDPs
thought to have originated form comets [8]. At least
some nanodiamonds are believed to be pre-solar based
on their excesses of the heavy isotopes of noble gases
such as Xe and the trace elements Te and Pd [9-12].
These isotopes may have a supernova origin.

Diamond dominates the residues of primitive
meteorites after extreme acid dissolution and chemical
oxidation. The dissolution removes the majority of
minerals and sp2-bonded carbon leaving primarily
diamond with a few percent of acid resistant minerals,
e.g. [1]. Transmission electron microscopy (TEM)
images of the residue show a m?lange of nanometersized
diffracting domains. Despite many decades of
research on nanodiamonds, relatively little is know
about their location within the meteorite matrix. To
begin to answer this question I have started to
undertake work on locating nanodiamonds in the
primitive meteorite matrices. Initial work is being done
to find diamonds in the HF/HCl residue used to
prepare the insoluble organic matter (IOM). The
experience with finding diamonds in the IOM residue
is then used to find diamonds in the raw, but
disaggregated, meteorite matrix.

Click on the link below for the whole article

http://www.lpi.usra.edu/meetings/lpsc2010/pdf/1388.pdf

Shawn Alan
eBayshop
http://shop.ebay.com/photophlow/m.html?_nkw=&_armrs=1&_from=&_ipg=

______________________________________________
Visit the Archives at
http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list mailing list
Meteorite-list at meteoritecentral.com
http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Mon 17 May 2010 01:09:39 AM PDT