[meteorite-list] Meteorite Yields Carbon Crystals Harder Than Diamond

[STARSANDSCOPES at aol.com]

Hi list,  This is off topic (sort of)  to  this very interesting post but 
it 
does mention graphite and  diamonds.   

I have shared this observation before and every  time I have mentioned it  
I 
have been taken wrong!  Has any else  noticed how the graphite inclusions  
in the fossil EL3, NWA 2828, 2965,  Al Haggounia 001 etc. fool an 
electronic  
diamond tester?

Now  this is the part I have been taken wrong on, I'm not  saying I have  
found testable size diamonds but rather the graphite will set off  an  
electronic diamond tester!  Those testers operate on thermal   
conductivity.  

I can take my optical scopes to 2000X but that is  no  help in this stuff.

I have tried similar inclusions in other  meteorites  and nothing.  Is the 
inclusion made of nano diamonds  or just a material  that is as thermally 
conductive as  diamonds?   Which ever, it is  interesting!

Tom  Phillips

In a message dated 2/3/2010 6:23:57 P.M. Mountain Standard Time,  baalke
@zagami.jpl.nasa.gov  writes:

http://www.physorg.com/news184402061.html     

Meteorite yields carbon crystals harder than diamond
by Lin  Edwards
physorg.com
February 3, 2010 

(PhysOrg.com) -- Two new  types of ultra-hard carbon crystals have been
found by researchers  investigating the ureilite class Haverö meteorite
that crashed to Earth in  Finland in 1971. Ureilite meteorites are
carbon-rich and known to contain  graphite and diamonds.

The super-hard diamonds were created when graphite  in the meteorite
experienced the intense heat and pressure of entering the  Earth's 
atmosphere and crashing into the ground. The graphite layers would  
have been heated and shocked enough to create bonds between them, in  
much the same way as humans manufacture
diamonds.

The new carbon  crystals were too small to test for precise hardness but
they are known to be  harder than normal diamonds because the researchers
found them by using a  diamond paste to polish a slice of the meteorite.
The crystals were raised  more than 10 µm above the polished surface,
which meant they were harder than  the diamonds in the polishing paste.
The researchers had seen carbon crystals  that resisted the diamond
polishing in one direction before, but the new  crystals were unaffected
when polished in every direction.

The  scientists then used an array of mineralogical instruments,
including  microscopy, spectroscopy and energy-dispersive X-rays among
others, to study  the structure of the crystals. This allowed them to
identify them as  representing two new carbon polymorphs or diamond
polytypes.

One is an  ultra-hard rhombohedral carbon polymorph similar to diamond,
while the other  is a 21R diamond polytype ultra-hard diamond. The
existence of ultra-hard  diamonds had been predicted decades ago, but
they have never before been  found in nature. The novel form consists of
fused graphite sheets similar to  artificial diamond.

Professor Tristan Ferroir, leader of the research  team from the
Université de Lyon in France, said the discovery was  accidental, but
they had thought an examination of the meteorite would "lead  to new
findings on the carbon system."

Professor Ferroir said there is  currently no way to compare the
structure of the new crystals to boron  nitride and lonsdaleite, the 
artificially manufactured ultra-hard diamonds,  but the findings help 
scientists gain a better understanding of carbon  polymorphs and give 
them new materials to investigate and perhaps  synthesize. They also 
show the carbon system is more complex than previously  thought.

The findings on the new diamond were published in the Earth  and
Planetary Science Letters journal on February 15.

More  information:*  http://dx.doi.org/10.1016/j.epsl.2009.12.015
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