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, [email protected] <[email protected]> wrote:
From: [email protected] <[email protected]>
Subject: Re: [meteorite-list] WHERE ARE THE NANODIAMONDS IN PRIMITIVE
METEORITES? PREL...
To: [email protected], [email protected]
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,
[email protected] 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,
[email protected]
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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