[meteorite-list] Black Diamonds: A interesting PBS NOVA article

From: Fries, Marc D <marc.d.fries_at_meteoritecentral.com>
Date: Mon, 13 Apr 2009 08:27:21 -0700
Message-ID: <C608A7E9.76F0%Marc.D.Fries_at_jpl.nasa.gov>

Howdy Stirling

    You get nanocrystalline diamond from nitrogen in the source
gases/liquids. This happens because nitrogen will substitute for carbon in
the diamond crystal lattice, but it brings an extra electron with it. The
crystal solves that problem by incorporating a vacancy defect for every
nitrogen defect. Add enough nitrogen and you wind up with diamond that is
loaded with defects and won't grow large, clear crystals - exactly what you
see with carbonadoes. Nitrogen also multiplies the growth rate and the
nucleation density, so the whole thing grows quickly as diamond goes - as
much as mm's per hour. Note that that growth rate most likely discounts
formation in the initial fireball after a large impact. It also doesn't
matter how the diamonds are made - nitrogen will have the same effect.

    Carbonadoes are very cool. They're also maddening, because we've got a
lot of data about them but there are multiple reasonable explanations for
most of their attributes! I'm glad to see all this interest in them, and
I'm pretty confident that someone will "solve" them in my lifetime.

    Now, back to my place at the oars...

Cheers,
MDF


On 4/12/09 1:02 PM, "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
wrote:

> Hi, Marc, List,
>
> I'm not competent enough in this area to
> have an opinion worth much but I find it
> difficult to imagine how a loose, open crystal
> structure, amorphous hexacrystalline carbon
> could form "naturally" in the titanic pressures
> at the depths where diamonds are made; I
> always read it was 50 to 90 miles down.
>
> On the other hand, it makes intuitive sense
> it should happen in a zero-gee or low-gee
> environment even if shock is involved. It also
> spoils my picture of somebody landing on a
> small asteroid and finding it to be one giant
> diamond the size of Manhattan!
>
> Or at least a diamond as big as the Ritz-Carlton
> Hotel in Manhattan, a notion about diamond
> size that occured long ago to F. Scott Fitzgerald
> http://www.readbookonline.net/read/690/10627/
> in his story "The Diamond As Big As The Ritz"
> (1922).
>
>
>
> Sterling K. Webb
> -------------------------------------------------------------------
> ----- Original Message -----
> From: "Fries, Marc D" <marc.d.fries at jpl.nasa.gov>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Sunday, April 12, 2009 1:57 PM
> Subject: Re: [meteorite-list] Black Diamonds: A interesting PBS NOVA
> article
>
>
> Wish I?d seen this one when it came out; I?d have gladly written a
> rebuttal
> paper. Not quite sure how they can claim there is a "complete absence
> of a
> deep Earth fingerprint", especially since they point out the low
> delta-C13
> values in carbonadoes themselves. The same range of values is seen in
> reduced carbon from both terrestrial and martian igneous rocks, as other
> papers have noted. Nitrogen has been noted in mantle fluids numerous
> times
> as well and could easily be the source of the nitrogen in carbonadoes.
> I've
> never seen "planar defect lamellae" in a carbonado, which this paper
> mentions but doesn't show. Planar defects can be simply the result of
> strain while buried, and only for silicates have the criteria for
> distinguishing strain-induced lamellae from shock-derived PDF's been
> established. All of the features of carbonadoes can be explained by
> formation in a deep-Earth environment from carbonaceous fluids or gases
> with
> the caveat that it would have to be a very reducing environment. There
> are
> two comments to be made about that - 1) that very fact has been used to
> explain away the possibility that a natural reactor is the source of
> carbonadoes, and 2) it would be a rare environment, but that is
> consistent
> with the fact that carbonadoes have basically only been found once in
> Earth's historical record. It also only requires a casual perusal of
> the
> mineral record to see examples of extremes of both reducing and
> oxidizing
> environments in the Earth's crust.
>
> Beyond this note, I'm really too busy to get into this. Carbonadoes are
> very cool and still mysterious, but I have yet to see a convincing
> argument
> that they are extraterrestrial. I've examined a few myself and found
> them
> to be a marvelous oddity, but a terrestrial oddity. I certainly
> wouldn't
> evoke an asteroid-sized diamond impactor to explain them.
>
> Cheers,
> MDF
>
> On 4/10/09 9:28 PM, "Steve Schoner" <schoner at mybluelight.com> wrote:
>
>> Here is the first article by Stephen Haggarty and others:
>>
>>
http://www.garai-research.com/research%20statement/carbonado/carbonado-infrar>>
e
>> d.htm
>>
>> Looks to be a very compelling argument.
>>
>> Steve.
>>
>> [meteorite-list] Black Diamonds: A interesting PBS NOVA article
>> Paul bristolia at yahoo.com
>> Fri Apr 10 23:15:49 EDT 2009
>>
>> * Previous message: [meteorite-list] Gamma Ray Burst caused mass
>> extinction? (With URLs to PDF Files)
>> * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
>>
>>
>> Steve Schoner wrote:
>>
>> "Here is a very interesting PBS article on carbonados.
>>
>> http://www.pbs.org/wgbh/nova/diamond/sky2.html "
>>
>> Also look at:
>>
>> Kagi, H. and S. Fukura, 2008, Infrared and Raman spectroscopic
>> observations of Central African carbonado and implications for
>> its origin. European Journal of Mineralogy. vol. 20, no. 3,
>> pp. 387-393, DOI: 10.1127/0935-1221/2008/0020-1817
>> http://eurjmin.geoscienceworld.org/cgi/content/abstract/20/3/387
>>
>> McCall, G.J.H., 2009, The carbonado diamond conundrum.
>> Earth-Science Reviews. vol. 93, no. 3-4, pp. 85&#8211;91.
>> http://dx.doi.org/10.1016/j.earscirev.2009.01.002
>>
>> Yokochi, R., D. Ohnenstetter, and Y. Sano, 2008, Intragrain
>> Variation in g13C And Nitrogen Concentration Associated
>> with Textural Heterogeneities of Carbonado. The Canadian
>> Mineralogist. vol. 46, no. 5, pp. 1283-1296, DOI:
>> 10.3749/canmin.46.5.1283
>> http://canmin.geoscienceworld.org/cgi/content/abstract/46/5/1283
>>
>> Diamonds, II: Diamond and Carbonado: Crystal Habits and Surface
>> Morphology
>> http://www.turnstone.ca/diamond2.htm
>>
>> yours,
>>
>> Paul H.
>>
>>
>>
>>
>> ____________________________________________________________
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Received on Mon 13 Apr 2009 11:27:21 AM PDT