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

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun, 12 Apr 2009 15:02:50 -0500
Message-ID: <82E2FB0B4E6D446DA6DFD88631A397D1_at_ATARIENGINE2>

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-infrare
> 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 Sun 12 Apr 2009 04:02:50 PM PDT