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

[Starsinthedirt 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 mélange 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=

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