[meteorite-list] WHERE ARE THE NANODIAMONDS IN PRIMITIVE METEORITES? PRELIMINARY TEM RESULTS

[Shawn Alan]

Tom, List
 
I am happy your enjoying the nanodiamond series. As for the electronic diamond detector which band do you have? I hear and have read that the
Gemoro ULTRATester II Diamond Moissanite Sapphire Tester with ULTRAdock is a great diamond detector.
 
I can see how graphite might trick a diamond detector in thinking its a diamond cause its a carbon base element. I bet graphite too is a good conductor with heat.
 
Here is something I just found on graphite from this website
http://www.galleries.com/minerals/elements/graphite/graphite.htm
 
Definition and write up from the link:

Graphite: is a polymorph of the element carbon. diamond is another polymorph. The two share the same chemistry, carbon, but have very different structures and very different properties.

    * Diamond is the hardest mineral known to man, Graphite is one of the softest.
    * Diamond is an excellent electrical insulator, Graphite is a good conductor of electricity.
    * Diamond is the ultimate abrasive, Graphite is a very good lubricant.
    * Diamond is usually transparent, Graphite is opaque.
    * Diamond crystallizes in the Isometric system and graphite crystallizes in the hexagonal system. 

write up from the link:
Somewhat of a surprise is that at surface temperatures and pressures, Graphite is the stable form of carbon. In fact, all diamonds at or near the surface of the Earth are currently undergoing a transformation into Graphite. This reaction, fortunately, is extremely slow.
All of the differences between graphite and diamond are the result of the difference in their respective structures. Graphite has a sheet like structure where the atoms all lie in a plane and are only weakly bonded to the graphite sheets above and below. Diamond has a framework structure where the carbon atoms are bonded to other carbon atoms in three dimensions as opposed to two in graphite. The carbon-carbon bonds in both minerals are actually quite strong, but it is the application of those bonds that make the difference.

It may seem strange that one of the softest minerals (and a very slippery lubricant) is the high-strength component in composites used to build automobiles, aircraft, and of course golf club shafts.  It is the weakly bonded sheets that slide by each other to yield the slipperiness or softness.  Yet when those sheets are rolled up into fibers, and those fibers twisted into threads, the true strength of the bonds becomes apparent. The threads are molded into shape, and held in place by a binder (such as an epoxy resin). The resulting composites have some of the highest strength-to-weight ratios of any materials (excluding, of course, diamond crystals and carbon nanotubes).

Graphite can only be confused with the mineral molybdenite which is metallic bluish silver in color. However, molybdenite is much denser and has a silver blue streak.

Most graphite is produced through the metamorphism of organic material in rocks. Even coal is occasionally metamorphosed into graphite. Some graphite is found in igneous rocks and also as nodules inside of iron meteorites.
 
But this might be different from presolar graphite too.
 
Here is something else I found about the origains of presolar grains and where they come from:

http://iopscience.iop.org/0004-637X/631/2/976/pdf/0004-637X_631_2_976.pdf
 
Abstract from the link:
The chemical, isotopic, and microstructural

information preserved in these grains can be extracted with TEM

and NanoSIMS analyses and used to form a more detailed and

accurate picture of grain condensation in stellar outflows. The isotopic

compositions of individual presolar grains often permit inferences

as to the types of stellar sources that produced them, such
as asymptotic giant branch (AGB) stars and supernovae.
 

 
I would have to agree that graphite and the nanodiamonds could set off a diamond detetor, it would be interesting to take that detector and test it with some Tagish Lake and see what happens. Why I suggest that is because Tagish Lake has the highest amount of nanodiamonds present in the meteorite then any other meteorite out there. One other note to add, Canyon Diablo is know to have diamonds included in it.
 
Shawn Alan



--- On Sun, 5/16/10, Starsinthedirt at aol.com <Starsinthedirt at aol.com> wrote:


From: Starsinthedirt at aol.com <Starsinthedirt at aol.com>
Subject: Re: [meteorite-list] WHERE ARE THE NANODIAMONDS IN PRIMITIVE METEORITES? PREL...
To: photophlow at yahoo.com, meteorite-list at meteoritecentral.com
Date: Sunday, May 16, 2010, 11:09 PM


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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